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Title: General Anatomy, Applied to Physiology and Medicine, Vol. 2 (of 3)
Author: Bichat, Xavier
Language: English
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                           GENERAL ANATOMY,

                              APPLIED TO

                       PHYSIOLOGY AND MEDICINE;

                           BY XAVIER BICHAT,

       PHYSICIAN OF THE GREAT HOSPITAL OF HUMANITY AT PARIS, AND
                 PROFESSOR OF ANATOMY AND PHYSIOLOGY.

                      Translated from the French.

                        BY GEORGE HAYWARD, M.D.

         FELLOW OF THE AMERICAN ACADEMY OF ARTS AND SCIENCES,
               AND OF THE MASSACHUSETTS MEDICAL SOCIETY.

                       _IN THREE VOLUMES._

                             VOLUME II.

                            _BOSTON_:
                   PUBLISHED BY RICHARDSON AND LORD.

                       J. H. A. FROST, PRINTER.
                                 1822.



DISTRICT OF MASSACHUSETTS, _to wit_:

  DISTRICT CLERK'S OFFICE.

BE IT REMEMBERED, that on the seventeenth day of April, A.D. 1822,
in the forty-sixth year of the Independence of the United States of
America, _Richardson & Lord_, of the said District, have deposited
in this office the title of a book, the right whereof they claim as
proprietors, in the words following, _to wit_:

"General Anatomy, applied to Physiology and Medicine; by Xavier Bichat,
Physician of the Great Hospital of Humanity at Paris, and Professor of
Anatomy and Physiology. Translated from the French, by George Hayward,
M. D. Fellow of the American Academy of Arts and Sciences, and of the
Massachusetts Medical Society. In three Volumes. Volume II."

In conformity to the Act of the Congress of the United States,
entitled, "An Act for the Encouragement of Learning, by securing the
Copies of Maps, Charts and Books, to the Authors and Proprietors of
such Copies, during the times therein mentioned:" and also to an Act
entitled, "An Act supplementary to an Act, entitled, An Act for the
encouragement of Learning, by securing the Copies of Maps, Charts and
Books, to the Authors and Proprietors of such Copies during the times
therein mentioned; and extending the Benefits thereof to the Arts of
Designing, Engraving and Etching Historical and other Prints."

  JOHN W. DAVIS,
  _Clerk of the District of Massachusetts._



CAPILLARY SYSTEMS.


The two great vascular systems, with red and black blood arise and
terminate, as we have said, in the capillaries, which form in the
lungs, as in all the other parts the limits that separate them, and in
which they are changed from one to the other. There are then evidently
two capillary systems distinct from each other, and which are even
opposite. One, generally spread throughout the body, is the seat of
the change of red blood into black. The other, confined wholly to the
lungs, exhibits an opposite phenomenon; it is in its divisions that the
black blood becomes red.

As the capillaries, which serve for the origin and termination of the
black abdominal blood, are intermixed on both sides with those of the
general capillary system, since in the abdomen they are continued with
the arteries and in the liver give origin to the veins, I shall omit
them in these remarks, and attend only to the general and pulmonary
capillary systems.

These two capillary systems, the first especially, deserve the more
particular consideration, 1st, because the circulation is governed
in it by laws wholly different from those of the other parts; 2d,
because most of the important functions of life take place there, as
secretions, nutrition, exhalations, &c.; 3d, because their small tubes
are affected on many occasions by diseases, as they are the seat of
inflammations, metastases, &c.; 4th, because animal heat is especially
produced in these tubes, &c.

The lowest species of animals have in reality only a capillary
circulation. Their fluids do not move in great masses, in canals which
carry them to all parts of the body, and afterwards bring them back
again. There is only an insensible oscillation of these fluids, in
tubes of the greatest delicacy and number. This kind of circulation is
one of the points of contact, or rather of transition from animals to
vegetables, which, destitute of the circulation with a sensible motion,
have evidently like the zoophytes, that of an insensible motion and of
the capillary vessels.

I shall first examine the general capillary system, and afterwards the
pulmonary.


ARTICLE FIRST.

OF THE GENERAL CAPILLARY SYSTEM.

This system exists in all the organs; all are in fact composed of an
infinity of capillaries, which cross, unite, separate and unite again,
by communicating in a thousand ways with each other. The vessels of
any considerable size, those among the arteries, in which the blood
circulates by the influence of the heart, and those among the veins,
which correspond to the first, have really no connexion with the
structure of the organs; they wind along their interstices; and are
lodged in the cellular texture that separates their lobes; but the
capillaries alone essentially make part of these organs, they are so
combined with them; that they truly enter into the composition of
their texture. It is in this view, that we may with truth consider the
animal body as an assemblage of vessels.

From this first view, it is evident that the extent of the general
capillary system is immense, that it embraces all the smallest
divisions of our bodies, so that we can hardly conceive of any organic
particles united without capillaries. It follows hence, that this
system is not only an intermediate one between the arteries and the
veins. It is from it, that all the exhalants, all the excretories,
&c. go. It furnishes all the vessels that carry nutritive matter to
our organs; we ought to describe it then as existing in parts where
arteries do not penetrate, as well as in those where they do.


I. _General Division of the Capillaries._

Since this system is not destined merely to unite the arteries to the
veins, and change the black blood to red, it is evident that other
fluids besides the blood, must circulate in them; this is in fact what
observation proves. There are many parts in the animal economy, in
which white fluids alone circulate. We know the hypothetical opinions
of Boerhaave upon the white arteries, the decreasing vessels, &c. We
shall find these opinions in all books; I shall only say here what
accurate observation shows us. That there is in the general capillary
system, parts in which the blood especially moves, others pervaded
only by white, or greyish fluids, &c. is a thing of inspection, and
has no need of proofs. But what is the proportion of these fluids in
the different organs? it is this that must be examined; now there are
parts where the blood predominates almost exclusively in the capillary
system, others where it exists in part, and in which there is a portion
of different fluids, others in fine in which these fluids alone are
found.


_Of the Organs in which the Capillaries contain only Blood._

It appears that in the muscular system, in the spleen, in certain
parts of the mucous surfaces, as in the pituitary membrane, &c. the
blood so predominates in the capillary tubes, that almost every other
fluid is unknown in them; thus fine injections demonstrate few other
vessels; the arteries and the veins are seen there in great abundance.
The blood, or its colouring matter, is in them, as I shall say, in two
different states; in one, it stagnates and serves then to colour the
organ; in the other, it circulates and contributes to its nutrition,
its excitement, &c.


_Of the Organs in which the Capillaries contain Blood and Fluids
differing from it._

These organs are the most numerous in the animal economy. The bones,
the cellular texture, the serous membranes, a part of the fibrous
system, the skin, the vascular parietes, the glands, &c. &c. exhibit
this arrangement in a very remarkable manner.

To give an idea of the capillary system in this kind of organs, let us
take one in which it is easy to examine it, the serous membranes, for
example. When we lay them bare in a living animal, their transparency
permits us to see in an evident manner that they contain but very
little blood in their capillary system; there are many branches under
them, but they appear to be only contiguous; raise, for example, in a
small living guinea-pig the peritoneal coat of the stomach; the red
arteries, which at first view appeared to be in this coat, remain
untouched. These membranes, certainly owe their white or greyish colour
to the small quantity of blood they receive from their small vessels,
to which the next trunks give rise. After having thus exposed a serous
membrane, in order to see the quantity of blood that is found in it in
a natural state, irritate it with any stimulant; at the end of some
time, it will be covered by an infinity of reddish streaks, which will
be so numerous, that they will change its whiteness into the red colour
of the mucous surfaces.

Force fine injections into a dead body, they will so fill the capillary
system of the serous surfaces, of those of the peritoneum, for example,
that those surfaces will be wholly black, and appear formed only by
a net-work of vessels, whilst very few are apparent in the living
body, because it is not the blood that fills them. When we cannot open
animals to convince us of this, surgical operations, in which the
intestines are laid bare, the peritoneum being untouched, wounds of the
abdomen, the cesarian operation, &c. will prove incontestably that in
the natural state, the blood fills ten and even twenty times less of
the vessels, upon the serous surfaces, than injections show us in their
texture.

Examine these surfaces in chronic and acute inflammations, of which
they are the seat, in the first especially, they exhibit a vascular
net-work, so full of blood, that their redness is often deeper than
that of the muscles.

All the organs of which I have spoken above, exhibit the same
phenomenon. Observe what takes place in the skin; fine injections show
there infinitely more vessels than are filled with blood in a natural
state; the face of a child well injected, is wholly black. Who does not
know that oftentimes from the effect of passion, the blood fills with
great rapidity, in the skin of the cheeks, numerous vessels, which in a
calm state of mind are not apparent?

Examine the conjunctiva, taken as an example in inflammations;
frequently in a short time it changes its white to a bright red,
because the blood fills vessels, in which it did not before pass; you
can easily distinguish these vessels with the naked eye; you can see
that the blood accumulated in this membrane, is not effused, but that
it is contained in real vessels.

I take for example the organs that have one of their surfaces free from
adhesion, because the state of the capillary system is more easily
distinguished in them; but the others present the same phenomenon; we
shall see that the cellular texture, certain fibrous organs, &c. &c.
examined comparatively, on the one hand in animals that we dissect
alive, on the other in an inflammatory state or after fine injections,
present a much less number of vessels in the first, than the second
case.

It can then be established as an incontestable fact, that in many of
the organs of the animal economy, the general capillary system is,
in the ordinary state, entered in part by blood, in part by other
different fluids, that appear to be white.

The proportions vary singularly; thus the capillary system of the
serous membranes contains hardly any blood as I have said; that of the
skin more; the mucous surfaces still more, &c. But whatever may be the
relation, the difference is not less real in the capillary system.

Perhaps also there are always in this system empty vessels, destined
to receive fluids under certain circumstances; thus the urethra, the
excretory ducts in certain cases, the orifices of the lacteals in the
intervals of digestion, contain nothing. It is difficult to conceive
of the rapidity of the passage of the blood in the capillaries of the
face, and in those of other parts of the skin, if these vessels contain
a fluid, which is to be displaced by the blood. However, nothing but
what is founded upon experiment can serve to decide this question.


_Of the Organs in which the Capillaries do not contain Blood._

These organs are less numerous than the preceding. They are the
tendons, the cartilages, the hair, certain ligaments, &c. Dissected in
a living animal, not a single drop of blood escapes from these organs,
and yet there is no doubt that capillaries exist in them; oftentimes
very fine injections demonstrate them there. Inflammation, also,
frequently fills these capillaries with blood. Into the hair, this
fluid enters in the plica polonica, &c. The non-vascular appearance
of these organs in the living body, is illusory; it is because their
fluids are divided into very small streams, the circulation of them is
more slow, and their colour different from the blood, that we cannot
perceive them.


II. _Difference of Organs in respect to the number of their
Capillaries._

Though the capillaries exist every where, yet they are more or less
numerous in the different organs; in making fine injections, it is easy
to be convinced of this. What anatomist has not been struck by the
prodigious number of vessels in this way developed, upon the skin, the
serous surfaces, the cellular texture, &c. compared with those in the
fibrous organs, in the muscles even, &c.?

I have sought for the cause of this difference, and it has not appeared
difficult to find it, since where injections develop few capillaries,
there is only nutrition going on, as the bones, the muscles, the
cartilages, the fibrous bodies, &c. are a constant proof; on the
contrary, in all those in which many fluids enter, there are, besides
nutrition, other functions, such as exhalation and secretion. Hence why
a serous surface, almost as white as a cartilage in the living body,
becomes ten times darker than it by the same fine injection; why the
skin, compared to the fibrous organs, exhibits the same phenomenon;
why in proportion to the arteries that enter a muscle and a gland, the
latter admits much more injection than the other.

These observations, which are uniform and invariable, prove that the
capillary system is as much more developed in a part, as it has more
functions to sustain. Observe in fine, that it is a kind of depot
in which the fluids remain for a certain time, before serving for
nutrition, exhalation and secretion. Where these three functions are
united, it is necessary that there should be more fluids there, than
where only one of them exists; hence more capillary vessels.

The capillary system is not then in the organs in proportion to their
size; a portion of the pleura contains more vessels than a tendon that
is ten times larger. It is the nutritive substance that fills the place
that these vessels do not occupy.

We might, from what has just been said, divide the systems into two
classes, from the development of their capillaries; place on one side
the serous, the mucous, the glandular, the dermoid, the synovial,
the cellular, &c.; on the other the osseous, the cartilaginous, the
fibrous, the arterial, the venous, the fibro-cartilaginous, &c. The
first class surpasses the second, considerably, in the number of its
small vessels. Observe, also, that inflammation, different eruptions,
all the affections, in which there is, as it is called, an afflux of
humours to a part, are infinitely more frequent in the first than the
second class, because all these affections are essentially seated in
the capillary system, which is more developed in them.

Asphyxia, apoplexy, and all the affections that make the black blood
stagnate in the general capillary system, prove the same thing; in
fact, examine the livid head of one who has died of asphyxia, or of
apoplexy, you will see that it is especially in the skin and the
cellular texture that the blood is arrested; that the muscles, the
aponeuroses, exhibit besides the blood ordinarily found in them, only a
small quantity of superabundant fluid, in comparison with what there is
in the first organs.


_Remarks upon Injections._

From all that has been said, it is evident, that fine injections,
which form a convenient method of knowing the capillary system of an
organ, cannot show which vessels of this system admit red blood, and
which circulate only white fluids. In fact, the injected matter passes
equally into each, and we cannot distinguish that, which in the living
body is very distinct.

In order to form a precise and accurate idea of the quantity of
blood that enters each of the organic systems during life, it is
indispensably necessary to dissect those systems during life. I shall
frequently have occasion in this work, to make this truth felt, which
appears to me to be of much importance in many respects. If a fine
injection but partially succeeds, it almost always shows vessels that
really exist, but which were not sanguineous during life. Even the
coarse injections of our dissecting rooms frequently exhibit these
phenomena, especially in the face, the neck, &c.; and much more so, if
the matter injected is very delicate, and managed with much address. I
cannot conceive why physiologists have always taken as an indication of
the blood vessels, the state of injected organs; by opening any part of
a living animal, they may clearly see how deceptive this method is.

Injections are of no advantage except in the great vessels, in which
the blood circulates in a mass by the influence of the heart; in the
capillaries, they do not reach the precise point that exists in nature.

I wish that in dissecting rooms, the pupils, after having dissected
the arteries and veins, would finish their labours upon the vessels
by the dissection of a living animal, for the purpose of seeing the
quantity of blood that each system has in its capillaries; this
knowledge is essential to the study of inflammations, fungous tumours,
&c. Anatomical cabinets in which preparations are kept, are of no use
in this respect; these preparations are more likely to deceive in
proportion as the injections have succeeded well.


III. _Of the proportions which exist in the Capillaries between the
Blood and the Fluids that differ from it._

In the organs in which the blood, or the white fluids differing from
it, alone enter, there can be no variety in the proportions; but the
varieties are frequent in those where these fluids enter at the same
time. In the serous, the dermoid, the mucous systems, &c. there are
sometimes more, sometimes less small vessels filled with blood; the
cheeks, of which I have spoken, are a remarkable example of this.
The least emotion, the slightest agitation, or a motion a little too
violent, accumulates, diminishes, and varies, in a thousand different
ways, the quantity of blood in them. The whole exterior of the skin
exhibits the same phenomenon, though less frequently. When this organ
is irritated or excited at any point, it immediately reddens; it
becomes white if it is compressed. Cold and heat uniformly produce
analogous varieties, when the change from one to the other is sudden.
All the mucous surfaces exhibit the same arrangement; see the glans in
the erection of coition, or in the flaccidity that succeeds it; the
difference in the quantity of the blood that this external membrane
contains, is very evident. Lay bare a serous surface; at first
white, soon there will be numerous red streaks. If we could see the
capillaries of the glands, I presume that we should find the quantity
of blood variable in these vessels, and that during the time that the
secreted fluids are poured out in abundance, their system would be
more copiously supplied than at any of the time when it furnishes the
materials of the secretions. Why are not the kidnies and the liver
subject to the same varieties in the quantity of their blood, as the
surface of the skin? When, by a violent motion, sweat pours out in
abundance, and the external surface of the body looks more red, does it
not indicate that the blood is there in a greater proportion?

There are two things to be distinguished, however, upon this subject;
it is only when the copious secretions arise from an increase of
life, that a greater afflux of blood is supposed to take place in the
glandular system. When this increased secretion proceeds from a want
of vital energy, the blood is not in greater quantity in the gland.
The same observation applies to exhalation; thus, in the above case,
in the commencement of fever, &c. more blood enters the skin; but when
the sweat arises from weakness, as in phthisis, &c. there is not this
accumulation of blood in the capillary system. But this deserves a
longer explanation.


 _Different proportions of Blood in the Capillaries, according as the
 Secretions and Exhalations are active or passive._

I call those exhalations and secretions active, which are preceded
and accompanied by an evident development of vital forces; and
those passive which exhibit an opposite phenomenon. If we examine
the phenomena of the animal economy, it will be easy to see this
distinction, which appears to me essential in diseases; now, in
whatever organ you study it, you will always see every active
exhalation or secretion preceded by a greater afflux of blood to the
part; all passive exhalations and secretions present an opposite
phenomenon. Let us begin with exhalations.

1st. Cutaneous exhalation is active from violent running, or a paroxysm
of fever, as I have said, from the action of caloric upon the body,
hard work, &c.; the skin is then more expanded and deeper coloured;
more blood enters it, &c. This excitement of the skin makes it more
fit to be influenced by external agents, and to influence in its turn
all the other organs. It is the suppression of these transpirations
which causes so many accidents in the animal economy. Observe, on the
contrary, the complexion of the body in phthisical sweats, in those
produced by internal suppurations, in those that are the effect of
fear, in all those that are called colliquative, &c.; this complexion
is more pale than in a natural state; it is not capable of being
influenced, because its vital activity is then small, and its forces
languish.

2d. In the exhalations of the serous surfaces, there are some that are
essentially active; such is that of pus; for we shall see that the
formation of this fluid upon these membranes is without any kind of
erosion, that it flows evidently from the exhalants, instead of serum;
very often even it flows at the same time. Nothing is more frequent, in
fact, than the milky or purulent serum that is found in the peritoneum,
the pleura, &c. whether the fluids are exactly mixed, or the pus
floats in flakes in the serum. Now this active exhalation of serum or
of pus, which appears to be here principally coagulated albumen, this
exhalation, I say, is evidently preceded by a considerable accumulation
of blood in the capillary system, an accumulation which constitutes
inflammation, and without which exhalation cannot take place. Observe,
on the contrary, serous exhalation, increased by the weakness that any
organic disease gives to the serous membranes; to furnish this fluid,
the blood is never accumulated in them in greater quantity. Open the
membranous sacs, after the diseases of the heart, the womb, the lungs,
the liver, the spleen, &c. you will find them full of water, but more
diaphanous than usual, because they have received less blood.

3d. What I have said of the serous exhalations, must be said of the
cellular; some of them are active, such as those of pus and the
serum that sometimes accompanies it; others are passive, as the
leucophlegmasia after organic diseases. The same observation is to be
made as before; there is an accumulation of blood in the capillary
system in the first kind, a diminution of this fluid in the second.
Observe the fatty exhalation; a man in health who is very fat, has a
rosy colour upon the integuments distended with fat, which indicates
the abundance of blood in the capillary system. On the contrary, in
certain cases of sudden corpulency after diseases, in that which
is called false fat, and accompanies weakness, a general paleness
corresponding with the fatty bloating, indicates the absence of the
sanguineous fluid.

4th. Mucous exhalations present also an analogous phenomenon. I
shall prove soon that the hemorrhages from the mucous surfaces are
real exhalations; now some of them are active, a name which Pinel
has given them in his Nosography; these are the nasal, pulmonary,
gastric, uterine hemorrhages, &c. of young people and even of adults.
All these hemorrhages are accompanied by a local increase of action,
by greater heat, by a deeper colour of the mucous membrane, by the
greater abundance of blood in the capillary system. Who does not
know, that Galen predicted a hemorrhage from the redness which he
saw upon the nose and the eye of the patient? On the other hand,
observe the hemorrhages of the mucous surfaces, which take place
after long diseases, hemoptysis, which terminates the diseases of the
heart, hematemesis, the effect of organic derangement of the liver,
hemorrhages from the intestinal canal, so frequent at the end of all
the long organic diseases of the abdomen, &c. nasal hemorrhages in
certain low fevers, those which take place in scurvy from the different
mucous surfaces, the gums especially, &c. all these hemorrhages, which
are truly passive are not accompanied by this preliminary sanguineous
congestion in the capillaries, by this increased activity of vital
action; it might be said that it is the blood, which transudes, as
in the dead body, through the pores, that have not power to retain
it. This distinction is so true, that without making a theory of it,
physicians conform to it in their practice. We bleed to arrest an
active hemoptysis, but would you bleed to stop that which comes on in
the chronic diseases of the thorax? The same observation applies to
all the hemorrhages; they require means wholly opposite, according as
they are active or passive; a remark moreover that is applicable to
all diseases that have increased exhalations or secretions, whatever
may be their seat. It is not the phenomenon that we are to resist, but
the cause that has produced it. We diminish the forces, when serum is
accumulated in the thorax, from a pleurisy; we increase them, when it
accumulates from a disease of the heart, the lungs, &c.

What I have just said of exhalations applies to secretions. The mucous
glands pour out a greater quantity of fluids in two ways, sometimes
from irritation, sometimes from the want of force. When this happens
in the intestines, there results from it in the first case a diarrhœa
from irritation, in the second a colliquative one. Now it appears
that the blood enters the gland in greater abundance in the one than
the other case. Its increase takes place undoubtedly in most acute
catarrhs, in which there is active secretion of mucus; its diminution
or at least its want of increase is not less sensible in many chronic
catarrhs, in which we may consider the secretion as passive. We know
that the abundance of urine, of bile, sometimes supposes an increased,
sometimes a diminished action of the kidney and the liver. Is there not
a superabundance of semen from excess of vitality, and an unnatural
flow from weakness? All the secreted fluids have the same arrangement;
now according to these two opposite causes of the superabundance of
the secreted fluids, the capillary system of the glands is certainly
penetrated with a different quantity of blood. Though the phenomenon
be the same, the treatment in the diseases in which it is manifest,
is as in the preceding cases, wholly opposite, according as the local
increase or diminution of life concurs to produce it.


_Consequences of the preceding Remarks._

From all that I have said, it is evident that in the organs whose
capillary system contains in part blood, and in part different fluids,
the proportion of the first to the others is infinitely variable; that
a thousand causes in a state of health, as in that of disease, by
bringing to the organ more or less blood, can fill more or less its
capillary system.

The trunks and branches that go to an organ, are they more or less
dilated, according as the capillary system of this organ is more or
less filled with blood? For example, when the mucous glands pour out
fluid in the greatest quantity, are the neighbouring branches more
full? Some experiments that I shall mention hereafter do not seem to
prove it.


IV. _Of the Anastomoses of the General Capillary System._

All that has been said evidently supposes a free communication
established between all the parts of the capillary system; this
communication is in fact clearly demonstrated by observation. When we
examine a serous injected surface, of which the capillary system is
full, we see that this system is a real net-work with fine meshes, and
in which no vessel runs a distance of more than two lines, without
communicating with others. The passage then, is constantly open between
the portion that receives blood, and that which admits fluids differing
from it. The same arrangement exists in the dermoid system, in the
origins of the mucous, &c. and in general in all those in which the
capillary system contains blood and white fluids.

On the other hand, the organs in which we find only white fluids,
evidently communicate with those that are near them, and in which there
is blood; those in which blood alone flows, have the same arrangement.

The capillary system must then be considered as a general net-work,
spread throughout the body, which communicates on one side in every
organ, and on the other from one organ to another. In this respect
there is from the head to the feet a general anastomosis, a free
communication for the fluids. It is in this way that we can conceive
of the permeability of the body, and not from the cellular texture, in
which the serous and fatty fluids alone stagnate.

As the arteries enter the capillary system, and as the veins, the
exhalants, the secretories, go from it, it is evident from this manner
of considering the capillary system, that all these vessels ought to
communicate with each other; that by pushing a fine fluid into the
arteries, it should go out by the excretories, the exhalants, and
return by the veins, after having gone through the capillary system;
this is in fact what takes place. In this respect, a thousand ways
are constantly open for the blood to escape from its vessels, which
communicate thus everywhere without, and do not present any mechanical
obstacle to the blood in their cavity, which life alone retains within
the limits of its circulation. The oozings after death through the
exhalants, the excretories and the veins, are so well known, so many
anatomists have related examples of them, that I think it unnecessary
to give them in detail here. We have seen, then, fine injections pour
out upon the serous membranes, upon the pericardium, the pleura, the
peritoneum, &c. transude upon the mucous surfaces, even upon the skin.
We have seen them flow through the ureters, the pancreatic, biliary,
salivary ducts, &c. Haller, in the article upon each organ, has not
failed to relate examples of this sort, which prove the communication
of the arteries with all the other vessels, by means of the capillary
net-work. What anatomist has not sometimes made even coarse injections
return by the veins? The communication of these vessels with the
arteries, through the capillary system, is now an anatomical axiom. At
one time, it arrested much attention. It has been asked, if there was
any thing intermediate between the arteries and the veins; inspection
proves that the capillary system alone is there.

Hence it is necessary to represent the capillary system as a kind
of general reservoir, in which the arteries enter on one side, and
from which go out on the other side, in all the organs, the nutritive
exhalants, in some, certain particular exhalants, as those of the
sweat, the lymph, the fat, &c. in others the secretory vessels, &c. It
is a common reservoir, if I may so express myself, in which the red
blood enters, and from which the black blood, the exhaled, the secreted
fluids, &c. go out.

This idea is not hypothetical; the injections of which I have spoken
are the most evident proof of it. Let it not be said that it is a
transudation after death, analogous to that of the bile through the
gall-bladder: if it were so, not only the fine fluids injected would
go out by the excretories and the exhalants, and return by the veins;
but in oozing through the pores, they would fill the whole cellular
texture. On the contrary, nothing escapes into the cellular texture,
around the vessels by which the injection passes; there is then a
continuity of tubes from the artery which has received the fluid, to
the excretory, the exhalant, or the vein which transmits it.

These are the communications of the capillary system that explain
how the skin becomes livid on the place on which a dead body has
for a long time lain, as on the back, for example; how by turning a
dead body, so that the head may hang down, it becomes full of fluid;
how, on the contrary, by placing upright the body of one dead from
apoplexy, asphyxia, &c. the capillary system of the face is freed
in a great measure from the blood it contained; how an erysipelas
disappears on a dead body, when the blood, arrested during life on a
part of the skin, by the vital action, is spread after death to all the
surrounding parts; how every kind of analogous redness of the skin,
and even of the serous surfaces, disappears because the blood goes by
the communications of the capillary system to the neighbouring organs.
During life the tonic action retains the fluid in a determinate part;
abandoned to its gravity, and other physical causes, after death, it
soon disappears from the part in which it was accumulated, on account
of the innumerable communications of the general capillary system.

I would observe to those who examine dead bodies, that these
considerations are very important. Thus we must not judge of the
quantity of blood which penetrated the inflamed peritoneum or pleura,
by what is seen twenty-four hours after death; local irritation was a
permanent cause that fixed the blood in the part; this cause having
ceased, it escapes from it. A serous membrane may have been very much
inflamed during life, and yet exhibit almost its natural appearance
after death; as it is in erysipelas. I should have been often tempted
from opening dead bodies, to deny the existence of an affection which
had been real. The same remark applies to the inflamed cellular
texture, the mucous surfaces, &c. Examine a subject that has died of
angina, which during life gave the deepest red colour to the pillars of
the velum pendulum pelati, to the velum itself and the whole pharynx;
after death, the parts assume nearly their natural colour.

I would observe that in this respect it is necessary to distinguish
acute from chronic affections. In the chronic inflammations, for
example, of the pleura, of the peritoneum, &c. the redness continues
after death, because the blood is combined, as it were, with the organ;
it makes a part of it, as it makes a part of the muscles in a natural
state. So the chronic affections of the skin, of the mucous surfaces,
retain after death nearly the same blood, that they had during
life; whereas in acute affections, the blood retained for a time by
irritation, escapes when life has ceased, upon which this irritation
depended. These principles can be applied to many diseases; I repeat
it, they are of great importance in examining bodies. The neglect of
them has often led me into an error, upon the degree and even the
existence of acute inflammations, of which the organs that I examined
had been the seat.

 V. _How, notwithstanding the general communication of the Capillary
 System, the Blood and the Fluids differing from it, remain separate._

Since in the dead body, and consequently during life, there is in
the capillary system no organic obstacle to the communication of the
fluids through its small branches; since the general net-work that
these vessels form is everywhere free, how does it happen that the
blood does not pass into the part destined to the white fluids? how
is it that these do not enter where the blood is to circulate? Why
does not this fluid go out by the exhalants and the excretories, since
these tubes communicate with the arteries by the anastomoses of the
capillary system? This depends wholly upon the relation which exists
between the organic sensibility of each part of the capillary system,
and the fluid that it contains. That which carries the blood, finds in
all the other fluids irritants that make it contract at their approach;
and reciprocally, where the other fluids belong, the blood would be a
foreign fluid. Why does the trachea admit air, and reject every other
fluid? Why do the lacteals choose only chyle from the contents of the
intestines? Why does the skin absorb certain substances, and repel
others, &c.? It all depends upon this, that each part, each portion of
an organ, every organic particle, has its own sensibility, which is in
relation only with one substance, and repels others.

But as this kind of sensibility is remarkably subject to vary, its
relation to substances foreign to the organ changes also; thus the part
of the capillary system which rejected blood, admits it at the moment
when its sensibility has been increased. Irritate a part of the skin,
it reddens in an instant; the blood flows there; while the irritation
continues, it remains; when it ceases, it disappears. Whatever be the
external means which raise the cutaneous or mucous sensibility, we
observe the same phenomenon. We can in this way bring more or less
blood into some parts of the capillary system. Bring the hand to the
fire, the heat exalts the sensibility of its system, more blood enters
it; take it away, this property resumes its natural type, and the blood
is brought back to its ordinary quantity. The internal organs which
are subjected less to the causes of excitement, have less varieties in
their capillary system; yet, however, there are many, and all arise
from the same principle.

A series of organized tubes are unlike an assemblage of inert ones.
These last require mechanical obstacles to prevent the communication
of fluids with each other; where there is a communication between the
tubes, there is a communication in the fluids. On the contrary, in the
living economy, it is the peculiar vitality with which each tube is
animated, which serves for an obstacle and a limit to the different
fluids; this vitality performs the part of different machines that we
place in the communicating tubes, to separate them from each other.
Every organized vessel is then truly active; it admits or rejects
fluids which enter there, according as it is able or not to support
their presence. Disproportion of capacity has nothing to do with this
phenomenon; a vessel may have mere than four times the capacity of
the particles of a fluid, and yet refuse to admit them, if this fluid
is repugnant to its sensibility. It is in this point of view that the
theory of Boerhaave has a great defect.

At the period in which this physician wrote, the vital forces had not
been analyzed. It was necessary to employ physical forces to explain
vital phenomena; hence it is not astonishing that all his theories
are so incoherent. In fact, theories in the vital phenomena borrowed
from physical forces, exhibit the same inadequacy, as those would in
the physical phenomena borrowed from vital laws. What would you say,
if in explaining the motion of the planets, rivers, &c. they should
talk of irritability and sensibility? you would think it absurd; it is
equally absurd, in explaining the animal functions, to talk of gravity,
impulse, inequality of the capacity of the tubes, &c.

Observe, that the physical sciences made no progress until they
analyzed the simple laws that preside over their innumerable phenomena.
Observe also, that medical and physiological science was not accurately
explained, until the vital laws were analyzed, and it was shown
that they were everywhere the principles of the phenomena. See with
what ease all those of the secretions, exhalations, absorptions,
inflammation, capillary circulation, &c. are referred to the same
principles, flow from the same data, by deriving them all from their
real cause, the different modifications of the sensibility of the
organs which execute them. On the contrary, see how each presented a
new difficulty, when the mechanical causes were employed to explain
them.

From what has been said, it is then evident, that in the innumerable
variations of which the fluids of the capillary system are susceptible,
in the different portions of the system which they fill, there is
always antecedent variations in the sensibility of the vascular
parietes; these varieties produce the first.

It is especially in the capillary system and its circulation, that the
variations of the organic sensibility of the vessels produce varieties
in the course of the fluids; for as I have observed, in the great
arterial and venous trunks, in the heart, &c. the fluids are in too
large masses, and they are agitated by too strong a motion, to be thus
immediately subjected to the influence of the vascular parietes. Thus
when nature wishes to prevent the fluids from communicating in the
trunks, it places among them valves, or other analogous obstacles,
which become useless in the capillary system.

Though the anatomical arrangement be the same in the living and the
dead body, there is then a very great difference in the course through
the capillary system, in one and the other. Push, into the aorta of
an animal in whom you destroy life by opening this artery to fix in
it a syringe, different fine fluids; you will never see them fill the
capillary system, pour out by the exhalants, the excretories, &c. as
when the subject has been some hours deprived of life. The organic
sensibility inherent in the parts repels the injection; it can only
circulate in the great trunks, in which there is a large space. I
have injected, with other views, a great number of times, fluids by
the arteries and the veins; now, the capillary system is never filled
with these fluids; they circulate only in the great vessels, when the
animal can bear them. Mr. Buniva has also made comparative experiments
with injections upon living animals and those deprived of life; he has
experienced in the first a resistance which he has not found in the
other; now this resistance is in the capillary system, whose vessels
refuse to admit a fluid to which their organic sensibility is not
accommodated.


VI. _Consequences of the preceding principles, in relation to
Inflammation._

From what has been said thus far, it is easy, I think, to understand
what takes place in the inflammatory phenomena, considered in general.

If a part be irritated in any manner, immediately its organic
sensibility is altered, and increased. Without previous connexion with
the blood, the capillary system is then placed in relation with it; it
as it were calls it there; it flows there and remains accumulated until
the organic sensibility returns to its natural type.

The entrance of the blood into the capillary system is then a secondary
effect of inflammation. The principal phenomenon, that which is the
cause of all the others, is the local irritation which has changed
the organic sensibility; now this local irritation may be produced in
different ways; 1st, by an irritant immediately applied, as a straw
upon the conjunctiva, cantharides upon the skin, acrid vapours upon
the mucous surface of the bronchia or the nasal cavities, atmospheric
air upon any internal organ laid bare, as we see in wounds, &c.; 2d,
by continuity of organs, as when a part of the skin, of the pleura,
&c. being inflamed, those that are near it are also affected, and the
blood flows there, as when one organ is diseased, that which is near it
becomes so by the cellular communications; 3d, by sympathies; thus the
skin being seized with cold, the pleura is sympathetically affected;
its organic sensibility is increased, the blood immediately enters it
from every part. When this property is raised in one of these three
ways in the capillary system, the phenomena that result from it are the
same. For example, when in the pleura it is raised because the air is
in contact with this membrane, because the lungs that it covers have
been first affected, or because coin has seized upon the skin in sweat,
the effect is nearly analogous, as it respects the entrance of the
blood in the capillary system.

It is then the change that takes place in the organic sensibility, that
constitutes the essence and the principle of the disease; it is this
change which makes a pain more or less severe soon felt in the part;
then the sensibility that was organic, becomes animal. The part was
before sensible to the impression of the blood, but did not transmit
this impression to the brain; then it transmits it, and this impression
becomes painful. Irritate the healthy pleura in a living animal; it
does not suffer; irritate it on the contrary during inflammation, and
it gives signs of the most acute pain. Who does not know that most
often and almost always, a pain more or less acute is perceived in the
part, some time before it becomes red? Now this pain is the indication
of the alteration that the organic sensibility undergoes; this
alteration exists some time, often without producing an effect; this
effect, which is especially the afflux of blood, is subsequent.

It is the same of heat. I shall say hereafter how it is produced. It is
sufficient now to show that it is, like the passage of the blood in the
capillary system, only an effect of the change that has taken place in
the organic sensibility of the part; now this is evident, since it is
always consequent upon this change.

There happens then in inflammation exactly the reverse of what
Boerhaave thought. The blood accumulated according to him, in the
capillary vessels, and pushed _à tergo_ by the heart, as he termed it,
was truly the immediate cause of the affection, whereas, from what I
have said, it is only the effect.

If we reflect a little upon the innumerable varieties of the causes
which can alter the organic sensibility of the capillary system, it
will be easy to understand of what infinite varieties inflammation
is susceptible, from the momentary blush that comes and goes in the
cheeks, to the most serious phlegmon and erysipelas. We might make a
scale of the degrees of inflammation. By taking the cutaneous, for
example, we should see at the bottom the redness that arises and
disappears suddenly by the least external excitement upon the dermoid
system, which we can produce at will, and in which there is only an
afflux of blood; then those that are a little more intense, which
occasion cutaneous efflorescences of some hours, but without fever;
then those that continue for a day, with which there is some fever;
then erysipelas of the first order; then that which is more intense,
and which gangrene soon terminates. All these different degrees do
not suppose a different nature in the disease; the principle of them
is always the same; there is always, 1st, an antecedent increase of
organic sensibility, or alteration of this property; 2d, afflux of
the blood only if the increase is not great, afflux of the blood,
heat, pulsation, &c. if it is. As to fever, it is a phenomenon common
to every severe, acute local affection; it appears to depend on the
singular relation which connects the heart with all parts; it has
nothing peculiar in inflammation, but the particular modification it
receives from it.

The afflux of the blood in an irritated part takes place in
inflammation, as in an incision. In this the divided point has been
irritated by the instrument; soon the whole blood in the neighbourhood
flows there and escapes by the wound. This afflux is so evident a
result of irritation, that in a slight incision, the blood scarcely
flows at the instant of the division of the integuments, because there
is but little of this fluid at the divided place; but a moment after,
the irritation which has been felt, produces its effect, and it flows
in a quantity disproportioned to the incision.

When the alteration of the organic sensibility which produces
inflammation, has no varieties except in its intensity, the
inflammation itself differs only in degree. But the nature of the
alteration is oftentimes different; a feeble character is frequently
united with it; the part has then less redness, heat, &c. Other
modifications are also observed; now all these depend upon the
difference of the alterations that the organic sensibility experiences;
at least these alterations always precede them.

The influence of these alterations is not less evident when
inflammation terminates, than when it begins. If the organic
sensibility has been so raised, that it is as it were exhausted,
then the solid dies, and the fluid, which is no longer in a living
organ, soon becomes putrid. Examine the phenomena of every gangrene;
putrefaction is certainly only a consequence; there is always, 1st,
a desertion of the solids by the vital forces; 2d, putrefaction of
the fluids. The first is never a consequence of the second. When the
organic sensibility begins to diminish, the blood brought there by
inflammation is already susceptible of putrefaction; but the defect of
tone in the solid always precedes. There is this local phenomenon, as
well as the general, in putrid fever. It is incontestable that in this
fever, the blood has a tendency to be decomposed, to become putrid; I
will say further, that it often exhibits a commencing putrefaction.
The index of the alteration of this fluid is always the general state
of the forces of the solids; these have first lost their spring;
the symptoms of weakness are evident before those of putridity. All
the animal fluids tend naturally to putrefaction, which takes place
inevitably when life abandons the solids in which they circulate. In
proportion as the forces diminish in the solids, this tendency is
manifested. A commencement of putrefaction in the fluids during life,
is not a general phenomenon more improbable than the local phenomenon
of which we have spoken, viz. that the blood of an inflamed part
begins to putrefy and the part consequently becomes fetid, before the
organic sensibility has entirely abandoned the solid. It is only when
this ceases, that this putrefaction becomes complete; but then it is
extremely rapid, because it had commenced during life. So bodies that
have died of putrid fevers decompose with a rapidity far surpassing
those that have died of other diseases, because putrefaction had really
commenced before death.

Inflammation with a livid colour, small degree of heat, prostration of
the forces in the part, and termination by gangrene, is evidently to
well marked adynamic fever, what phlegmon is to inflammatory fever,
what irritation of the primæ viæ, which is called bilious affection,
is to the meningo-gastric fever, &c. I think if we examine attentively
local affections and general fevers, we shall always find a particular
kind of fever corresponding in its nature to a particular kind of local
affection. But let us return to inflammation.

If it terminates by suppuration, it is evident that there is a new
alteration of the organic sensibility to produce pus. The same thing
in scirrhus. The termination by resolution takes place when this
sensibility returns to its natural type. Examine well the inflammatory
phenomena in their succession; you will see, that always a particular
state in this property, precedes the changes they exhibit.

When our medicaments are applied upon an inflamed part, it is not upon
the blood that they act; it is not by lessening the heat, or relaxing.
The expressions _to soften_, _unbend_ and _relax_ the solids, are
inaccurate, because they are borrowed from physical phenomena. We
relax, we soften dry leather by moistening it; but we only act upon
the living organs, by modifying their vital properties. Observe that
though we already begin to recognize the empire of these properties in
diseases, medical language is still wholly borrowed from theories which
employ physical principles in the explanation of morbid phenomena. We
have arrived at a period when the manner of expressing ourselves upon
these phenomena should be changed; I do not here speak of the names of
diseases. Certainly every emollient, astringent, discutient, relaxing,
tonic, medicament, &c. employed with different views upon an inflamed
part, only acts by modifying differently from what it was, organic
sensibility. It is thus that our medicaments cure or often aggravate
diseases.

From what has been said, it is evident that the solids perform the
first part in inflammations, and the fluids only the second. Modern
authors have perceived this truth, and they have immediately assigned
an important part, in this respect, to the nerves; but we have seen
that these appear foreign to organic sensibility, that they are so
even after the most rigorous observation. The nervous influence, that
at least which we know in other parts, is, in inflammation, as in
secretion, exhalation and nutrition, almost entirely wanting. There is
in this affection, unalteration of the organic sensibility, and this is
every thing.

The kind of blood varies in inflammation, and in this respect, I
think the following rule is generally uniform; whenever the organic
sensibility is much raised, the life augmented and there is an increase
of forces in the inflamed part, then it is the red blood that remains
in the capillary system; then there is always great heat there. On
the contrary, when the inflammation approaches the putrid character,
the part becomes of a dull and livid colour; the capillaries appear
to be filled with black blood; the heat is less. In general, a bright
colour, in all eruptions analogous to inflammatory tumours, announces
the increase of the organic sensibility. A livid colour, on the other
hand, indicates its prostration; petechiæ are livid; scorbutic blotches
are so; a livid colour in tumours is the forerunner of gangrene. Do you
wish to know when cold acts as a stimulant? It is when it reddens the
end of the nose, the ears, &c. When these parts become livid, other
phenomena announce at the same time, that its action is sedative. This
is supported by my experiments upon life and death, which have proved
that the black blood everywhere interrupts the functions, weakens,
annihilates even the motion of the parts, when it is brought to them by
the arteries.


_Differences of Inflammation, according to the different Systems._

From what has been said upon inflammation, it appears that it has for
its seat the capillary system, for its principle an alteration in
the organic sensibility of this system, for its effect the afflux of
blood into vessels in which it did not before circulate, a consequent
increase of caloric, &c. Now where the capillary system is more
developed, where the organic sensibility is greater, inflammation
ought to be more frequent; and this is the case. It is especially in
the cellular, serous, mucous and dermoid systems that we observe it;
fine injections demonstrate in these systems a capillary net-work
infinitely superior to that of the others. Besides, as if there is not
only nutrition, but also exhalation and oftentimes secretion in these
systems, there must be more organic sensibility, a property from which
all these functions are derived.

On the contrary, inflammation is rare in the muscular, osseous,
cartilaginous, fibrous, arterial, venous systems, &c. where there are
but few capillaries, and where the organic sensibility presiding only
over nutrition, is necessarily found in a less degree.

Besides, as the capillaries make an integral part of the system where
they are found, and as each system has its peculiar kind of organic
sensibility, it is evident that they ought to partake of this kind; now
as it is upon this property that all the inflammatory phenomena depend,
they ought to present an aspect wholly different in each system. This
is what we shall be convinced is the case by an examination of each. I
shall only present here generally, that essential point of view, upon
which authors have not insisted.

Let us take first the systems most exposed to inflammation; we shall
see that phlegmon is the inflammatory kind of the cellular, erysipelas
that of the dermoid, and catarrh that of the mucous. We have not yet a
general name to express that of the serous; but who does not know how
it differs from the others?

In the systems rarely subject to inflammation, we know this affection
infinitely less than in the preceding; but there is no doubt that
it differs essentially. Compare the length and permanency of that of
the bones, with the rapidity and disposition to change of that of the
muscles, or rather of the fibrous bodies, in rheumatism.

The results of inflammation do not vary less than its nature; if
resolution does not take place, each has its own mode of suppuration.
Compare the pus of erysipelas, that of phlegmon, the milky or
flocculent fluid of the serous membranes, the whitish or greyish
humour, of a mucous consistence, that escapes from the membranes of
the same name after catarrh, the blackish sanies of the bones in
suppuration, &c. We shall see that some organs, as the fibrous bodies,
do not suppurate.

Gangrene once taken place, is everywhere the same, since it is only
the absence of life, and all dead organs have the same properties. But
according to the sum of organic sensibility which each system has, it
is more or less disposed to die after inflammation, in the midst of
others which retain their life. Who does not know that the carbuncle
which soon kills the part it seizes, only attacks certain systems; that
the osseous, the cartilaginous, the nervous, &c. are always exempt from
it?

The essential fault of every medical doctrine is that of considering
diseases too abstractedly; they are so modified in each system, that
their aspect is wholly different. If I may be allowed the expression,
it is always the same individual, but in entering each system, it has a
different appearance there, so that often you cannot recognize it. When
will medicine be so far advanced that the treatment will correspond
with these varieties? There should certainly be a general treatment of
inflammation; but it should be modified differently, according as we
apply it to phlegmon, erysipelas, catarrh, &c.

This then is a very evident proof of that peculiar character which
inflammation takes in each part. We know with what ease and rapidity
the blood flows to any part of the skin in consequence of irritation
there; prick or rub briskly a part of this organ, it reddens in a
moment. This takes place also, though less sensibly, on the mucous
surfaces. This is not equally seen upon the serous; I have frequently
ascertained this on living animals, when I have laid bare these
surfaces and irritated them in different ways. The afflux of the blood
does not immediately follow the irritation: there is always an interval
between one and the other, never less than an hour.


VII. _Structure, and Properties of the Capillaries._

What is the structure of the capillaries? So great is their tenuity
that we evidently cannot have upon this point, any kind of data founded
upon experiment and observation. Only it is very probable, it is even
certain, that this structure is modified differently in each organ,
that it is not the same in the tendons, the aponeuroses, the muscles,
&c. that it really partakes of the nature of the organ of which it
makes an integral part.

The membrane which lines the excretories, the arteries, the veins,
the exhalants, vessels which go into the system of the capillaries or
come out of it, is very like that of these capillaries; but it is not
certainly the same.

It is the diversity in the structure of the capillaries, according to
the organs in which they are found, which has an essential influence
upon the difference which the vital properties exhibit, particularly
the organic sensibility and the insensible organic contractility in
each system in which we examine them; hence peculiar modifications in
all those diseases over which these properties preside, and which are
seated especially in the capillaries, such as inflammations, tumours,
hemorrhages, &c. &c.

The difference in structure of the capillary system, sometimes becomes
manifest to the eye. Thus the spleen, the corpus cavernosum, instead of
presenting, like the serous surfaces, a vascular net-work in which the
blood oscillates in different directions, according to the motion it
receives, exhibit only spongy, cancellated textures, whose nature is
but little known, in which the blood appears often to stagnate, instead
of moving, &c.


VIII. _Of the Circulation of the Capillaries._

The circulatory phenomena are of two kinds in the capillary system:
1st, there is the motion of the fluids; 2d, the alterations which they
undergo.


_Motion of the Fluids in the Capillary System._

These fluids are, 1st, the blood; 2d, others differing from it in their
composition, though we only know their differences of appearance. Let
us examine the laws of the motion of each kind.

The blood, after it has entered the capillary system, is evidently
beyond the influence of the heart, and only circulates by that of
the tonic forces, or the insensible contractility of the part. If we
examine the phenomena of this capillary system but little, we shall
be easily convinced of this truth, which Bordeu first taught. The
capillary system is really the boundary, beyond which the influence of
the heart does not extend. Hence why all the vessels that go out of
this system, exhibit in the fluid they contain a motion that does not
correspond with that of the arteries that go to it. 1st. After what we
have said, there is no doubt of this, as it regards the veins. 2d. It
is also true as it respects the excretories. The increase of secretions
does not correspond with the increase of the action of the heart, nor
does their diminution with the diminution of the pulsations. Who does
not know, on the contrary, that often in a violent paroxysm of fever,
in which the agitation of the arterial blood is very great, all the
glands seem to shut up their ducts and not to pour out any fluid? 3d.
It is the same with all the exhalations; it is not when a fever is the
greatest, that we sweat the most, but when it is somewhat diminished.
Hemorrhages are evidently but an exhalation; now who does not know,
that the pulse is often very weak, when the blood flows abundantly from
the mucous surfaces of the womb, the nostrils, the bronchia, &c.? Who
does not know on the contrary that in extreme agitations of the heart,
most often the blood does not flow by the exhalants? Is the quickness
of the pulse increased during menstruation? It is the redness of the
capillary system, the abundance of the blood of this system, which is
often, as I have said, the forerunner of active hemorrhages; but it
is never the increase of the action of the heart. Oftentimes fungous
tumours, soft flesh that shoots up in wounds of a bad nature, polypi,
&c. pour out blood; the heart has nothing to do with these hemorrhages,
they come evidently from the capillary system. Who does not know, that
frequently when the exhalants pour out copiously serous fluids upon the
membrane of that name, in the production of dropsies, the heart is,
like all the other parts, in a state of real inertia?

Since then all the vessels going from the capillary system exhibit in
their motions no sort of harmony with those of the heart, it is evident
that the influence of this organ is interrupted, is terminated at the
capillary system.

Observe nutrition; it is clearly the capillary system that distributes
everywhere the materials that it has received by the impulse of the
heart; now the influence of this does not extend to the place where the
nutritive matter is deposited. In fact, its impulse everywhere equal
and uniform, pushes the blood with nearly an equal force to all parts,
with some exceptions in the fœtus. Now nutrition is on the contrary
extremely unequal; at one age, it is one part that takes more increase,
consequently receives more nutritive matter; at another age, it is
another organ. This inequality, is the first and principal phenomenon
of growth.

How can we reconcile with the sole and uniform impulse of the heart
in all parts, inflammation, the production of herpes, of different
eruptions, &c. which appear in some places? Would inflammation exhibit
so many aspects, according to the system it seizes, if the heart alone
presided over its development? All the difference between catarrh,
erysipelas, phlegmon, &c. would disappear; and there would be only what
arose from being nearer, or further from the heart.

Let us cease then to consider this organ as the sole agent which
presides over the motion of the great vessels and the small, which,
in these last, driving the blood abundantly to a part, produces there
inflammation, which by its impulse causes the different cutaneous
eruptions, secretions, exhalations, &c. The whole doctrine of the
mechanicians rested, as we know, upon the great extent which they gave
to the movements of the heart.

There are evidently two kinds of diseases in relation to the
circulation; 1st, those that affect the general; 2d, those that affect
the capillary circulation. Different fevers form especially the first
kind. Different eruptions, tumours, inflammations, &c. produce the
second; now, though many relations connect the second with the first,
it is not essentially dependant upon it; the following is the proof of
this; fevers can evidently only exist in animals with great vessels,
in those in which the fluids move in a mass; they cannot take place
in zoophytes and plants, which have only a capillary circulation;
yet these last classes of animals and all vegetables are subject to
all the affections that disturb the capillary circulation. Thus we
see upon plants many tumours; their wounds unite; two portions even
contract adhesions, as a graft proves. The diseases of their capillary
system are no doubt different from those of animals in their progress
and their nature; but they exhibit always the same general character,
because they are derived from the same properties, organic sensibility
and insensible contractility.

Since the diseases of the capillary system are not essentially
connected with those of the general vascular system, they are not
then dependant on it; the circulation of the first is but indirectly
subordinate to that of the second. Hence why the two circulations can
be separate; why more than half of the organized beings have only the
capillary. This is the most important, since it immediately pours out
the materials of nutrition, of exhalations, of absorption: thus it
exists in all organized beings. We cannot conceive of any one without
it, because we cannot conceive of any one that is not continually
composed and decomposed by nutrition.

From what we have thus far said, it is evident, that the blood after
it has arrived in the capillary system, is moved there only by the
tonic influence of the solids; now, as the least cause alters and
changes their properties, it is subject there to an infinity of
irregular motions. The least irritation makes it recede, advance,
deviate to the right, or the left, &c. In the ordinary state, it moves
generally in an uniform manner from the arteries towards the veins;
but at every instant it may find causes of irregular oscillations in
its innumerable anastomoses; hence, as we have seen, the necessity of
these anastomoses. These irregular oscillations in the motion of the
blood in the capillary system, can be seen with a microscope. Haller,
Spallanzani and others, whose experiments are too well known for me
to relate them here, saw them a hundred times. They saw the globules
advance, recede, move in many different directions in animals with
red and cold blood, when they irritated the mesentery or any other
transparent part. In animals with red and warm blood, in those even
whose mesentery is almost as transparent as that of the frog, as in the
guinea-pig, it has appeared to me infinitely more difficult to trace
the motion of the blood in the capillaries.

It is easy to see that all the phenomena of inflammation, of different
eruptions, of tumours, &c. are especially founded upon this
susceptibility of the blood, in the capillary system, to move in an
infinite variety of directions, wherever irritation calls it.

From what has been said, it is evident that there are times when the
blood passes with less rapidity through the capillary system, and
there are others, when it moves more quickly. How then is the relation
always preserved the same, between the arterial and the venous blood?
It is in this way; the irregular oscillations hardly ever take place
except in one part of the capillary system; in no case is the whole
of it affected; thus if the blood moves more slowly in the cutaneous
capillary system, its velocity is increased in the cellular, the
muscular, &c.

This is in fact an invariable law in the vital forces, that if on the
one hand they increase in energy, on the other, they diminish; we might
say, that there was only a certain quantity in the animal economy,
that this might be divided in different proportions, but it cannot be
increased or diminished. This principle results so evidently from all
the phenomena of the economy, that I think it unnecessary to support
it by numerous proofs; now, taking this as incontrovertible, it is
evident that one portion of the capillary system increasing its action,
only at the expense of the others, the sum total of blood transmitted
from the arteries to the veins remains always nearly the same. All the
systems are then, in this respect, supporters of each other; if nothing
passes by the capillaries of one, it is the same thing, provided the
capillaries of another transmit double the amount of fluid that they do
in an ordinary state.

Observe the blood in the cutaneous capillaries before the paroxysm
of intermittent fevers; it recedes from these capillaries; all the
surfaces that it reddened, become pale; the capillaries of the other
systems supply the momentary defect of the action of these. Who knows
if, in many cases where the skin becomes very red, when much blood
enters it, there is not in the other systems a paleness analogous to
that of the skin during the cold fit of fever? I not only think this
very probable, but I have no doubt of it. The external capillaries
certainly contain more blood in summer, whilst those of the internal
systems receive more in winter. There is then continual varieties in
the mode of the passage of this fluid through the general capillary
system; each system transmits by turns, more or less, according as it
is affected.

When we see the glands, frequently in a short time pour out an
enormous quantity of fluid, the serous, cutaneous, mucous exhalants,
&c. furnish also much greater proportions than in a natural state,
we are astonished that the circulation can at the same time continue
with the same regularity; we are not less so undoubtedly, when we see
on the contrary all the evacuations suppressed, and nothing goes out
from the animal solids; now in all these cases, it is the capillary
system, whose forces differently modified in the different parts,
re-establishes the general equilibrium which would inevitably be lost,
if the heart was the agent of impulse which pushed to the extremities
the secreted and exhaled fluids, and transmitted the black blood to the
veins.

Sometimes however a derangement almost universal takes place in the
capillary system, especially on the exterior; this takes place in
sudden changes of the air. Though the vital laws preside essentially
over the capillary circulation, yet the degree of pressure of the
surrounding air can modify it to a certain point; we have a proof of
this in cupping glasses, or in any other means that produce suddenly
a vacuum upon a part of the body; then the fluids pressed in the
neighbourhood by the external air, and not compressed on the contrary
at the place of the cupping glass, raise up and distend considerably
the skin. The sudden changes of the atmosphere produce upon the whole
body, though in a less degree, the effect of a cupping glass. If the
air is rarefied, the whole external capillary system is more full; even
the sub-cutaneous veins swell; a very considerable part of the blood
experiences then a derangement in its motion, between the two systems
with red and black blood. The harmony, the correspondence of these two
systems is disturbed; hence the uneasiness, the sense of weight, &c. of
which we are instantly relieved by a sudden change of the atmosphere.

The evacuation of the blood also establishes differences, though less,
in the capillary system. Bleeding is of two kinds; one lessens the
blood of the circulation of the great trunks; and then it is sometimes
red, as in arteriotomy; but most often it is the black, that is drawn
off; the other takes blood from the capillary circulation; this is
done by leeches, cupping, &c. Each produces a different change in the
course of the blood. Physicians formerly were desirous of knowing from
which vein they ought to bleed. I think it is much more important to
know when we should by bleeding, act upon the general circulation, and
when upon the capillary. In many local congestions, I do not think
that you can diminish the quantity of blood in a part of the capillary
system, by diminishing the mass of this fluid in the great trunks; you
might take a quarter at least of the blood that there then was in the
economy, if the part is irritated, the blood will still flow as much to
this part. On the contrary, you may double by transfusion, the mass of
this fluid in an animal, local inflammations will not arise, because
there must be a preliminary irritation before the blood flows towards,
and enters a particular part of the capillary system.

The fluids differing from the blood which circulate in the capillary
system, 1st. are evidently like it beyond the influence of the heart.
2d. The influence of the tonic powers presides over their motions. 3d.
They are consequently subject to irregular oscillations, according as
the capillaries are differently affected.

We know not the nature of most of these fluids, because they cannot
be subjected to our experiments. They are those that enter the
ligaments, the tendons, the aponeuroses, the hair, the cartilages, the
fibro-cartilages, a part of the cutaneous, mucous, serous surfaces,
&c. They communicate with the blood from which they arise, by the
capillary systems, they afterwards move in their own systems. In most
of the organs in which they exist alone, as in those called white,
they are very slow in their motion, because the sensibility of these
organs is obscure and dull. Thus different tumours, to the formation of
which they contribute, have, as we shall see, almost always a chronic
progress.

There are often in the animal economy those tumours, that are commonly
called lymphatic, though we are wholly ignorant of the fluids that
form them. They are found especially in the neighbourhood of the
articulations; but sometimes only the cartilages, the cellular texture,
the bones, &c. are the seat of these white tumours; it is important
to ascertain the characters that distinguish them from the tumours in
which the blood especially enters.


_Phenomena of the Alteration of the Fluids in the Capillary System._

We have just treated of the phenomena of the motion of the fluids in
the general capillary system; let us now speak of the changes which
they undergo there in their nature.

The blood exhibits a remarkable phenomenon in the general capillary
system; from red, which it was in the arteries, it becomes black. How
does this take place? It evidently can happen only in two ways, viz.
either by the addition or subtraction of some principles. Is it charged
with carbon and hydrogen? Does it deposit only oxygen in the organs?
Are these two causes united to give it its blackness? I think that it
will always be difficult to decide upon these questions, which do not
appear to me to be capable of any positive experiment. However, when
we see the arterial blood furnish all the organs with the materials of
their secretion, nutrition and exhalation, it is to be presumed that it
leaves in these organs, rather than takes from them, the principle of
its colour.

Sometimes the red blood passes through the capillary system, without
losing its colour; for example, when the blood has flowed for a long
time black from a vein, we sometimes see it come out red, or nearly so,
just before it ceases to flow. In opening the renal vein, I have two or
three times made this observation, which has, I think, been noticed by
some authors.

The blood becomes more or less black in the general capillary system.
If you have observed bleedings, you have undoubtedly seen in diseases
innumerable varieties in the colour of the blood that comes from
the vein. Has this fluid a different blackness in each part of the
capillary system? It has appeared to me that the difference is not
very great in this respect. I have frequently had occasion to open the
renal, saphena, jugular veins, &c. the blood has appeared to me to be
everywhere of nearly the same colour. I wished to see if the blood
returning from an inflamed part was more or less black; I made then
in the hind leg of a dog a number of wounds near each other, and left
them open to the air. At the end of three days, when the inflammation
appeared to be greatest, I opened high up on the diseased and the sound
limb, the saphena and the crural veins, in order to examine their blood
comparatively; I could discover no sensible difference. I bled a man
who had a whitlow with an inflammatory swelling of the whole hand,
and the inferior part of the fore arm; the blood appeared of the same
colour as usual. Yet, as the veins bring also the blood of parts not
inflamed, more minute researches must be made.

An object which deserves to be determined with precision, is this, viz.
the cases in which, in general diseases, there is an alteration in the
deep colour of the blood, and the symptoms which correspond with these
alterations. At present we only know that it is more deep coloured in
some cases and less so in others.


IX. _Of the Capillaries considered as the seat of the production of
Heat._

Every one knows the innumerable hypotheses that were made upon the
production of animal heat by the mechanical physicians. Modern
chemists, in showing the insufficiency of these theories, have
substituted one that has not less difficulties. The lungs are
considered by them as the place in which the caloric is extricated,
and the arteries, a kind of tubes, that carry the heat to all parts of
the body. The production of this great phenomenon belongs then wholly,
according to them, to the pulmonary capillary system. I believe, on the
contrary, and I have taught in my courses on physiology, that it is in
the general capillary system that it has its seat.

I shall not stop to refute the hypothesis of the chemists. When we
place on one side, all the phenomena of animal heat, and on the other,
this hypothesis, it appears so inadequate to their explanation, that
I think every methodical mind can do it without my assistance. These
phenomena are the following:

1st. Every living and organized being, both animal and vegetable, has
a temperature of its own. 2d. This temperature is nearly the same
in all ages in animals. 3d. It is entirely independent of that of
the atmosphere; it remains the same in a warm as in a colder medium.
4th. Caloric is often disengaged in health more abundantly in some
parts than in others. 5th. In inflammation there is evidently a more
considerable extrication of it. 6th. The vital forces, especially the
tonic power, have a very decided influence upon the extrication of
caloric. 7th. Each organ has its own temperature, and it is from all
these partial temperatures, that the general one arises. 8th. There
is oftentimes an immediate connexion between the respiratory and
circulatory phenomena, and those of the production of heat; the first
increasing, the second increase also in proportion. At other times this
relation does not exist.

If, below these phenomena, you place the theory of Lavoisier, Crawford,
&c. I do not believe you can make it accord with them, and conceive how
caloric, disengaged in the pulmonary capillary system can be spread,
as they say, through the whole animal economy. By admitting on the
contrary that this fluid is disengaged in the general capillary system,
it is easily understood. But let us explain this way of understanding
the production of animal heat.

The blood draws from two principal sources the substances that repair
the losses it has sustained. These sources are, 1st, digestion; 2d,
respiration; the first pours chyle into the blood, the other mixes
it with different aerial principles. Sometimes cutaneous absorption
introduces into it different substances. The mixture of the blood with
the new substances it receives, constitutes sanguification. Now these
new substances carry continually into this fluid, new caloric; for as
all bodies are penetrated by it, there can hardly be an addition of
a substance to the blood, without the addition of this principle. In
sanguification, caloric combines then with the blood, but it is not in
a free state; it becomes part of the fluid; it is one of its elements.

Thus charged with combined caloric, the blood arrives in the capillary
system; there it gives it out, wherever it undergoes changes. It is
in fact in this system that it is changed into nutritive substance,
into that of the secretions, exhalations, &c. All the functions in
which this fluid changes its nature, in which certain principles are
separated from it, to form certain substances destined especially
to particular uses, necessarily disengage its caloric. I cannot
say precisely how this happens, whether it is more in the internal
alterations that the blood undergoes in furnishing nutrition, or in
those destined to furnish secretion or exhalation. This only is the
general principle, and exhibits three things; 1st, the entrance of
caloric into the blood, with all the substances that repair its losses;
2d, the circulation in a combined state of the caloric newly entered;
3d, extrication of this combined fluid, to form free caloric by the
changes and different alterations that the blood undergoes in the
general capillary system, in forming the materials of the different
functions.

The extrication of caloric is, then, a phenomenon exactly analogous to
those of which the general capillary system is the seat. In nutrition,
in fact, there is, 1st, a combination of new foreign substances with
the blood; 2d, circulation in the great vessels of these substances
combined; 3d, separation of the nutritive substance to enter the
organs. So also the elements of the secreted fluids combine, then
circulate combined, then leave the blood to be thrown out. So, in fine,
every exhaled fluid combines, circulates, and is then separated from
the blood.

From this it is evident that, 1st, the entrance of foreign substances
into the blood by respiration, by digestion or even cutaneous
absorption; 2d, the combination of these substances with the blood
in sanguification; 3d, their circulation in the arterial system, are
three general phenomena common to secretions, exhalations, nutrition,
and calorification, if I may be allowed the term; for the production
of heat is a function and not a property; hence why I think the word
caloricity does not express it.

The caloric arrives, then, in the capillary system combined with the
matter of secretions, exhalations, and nutrition. The blood is the
common fluid that results from all these combinations. In the general
capillary system each part is separated; the caloric to be distributed
over the whole body and afterwards pass out; the fluids of the
secretions go out by the glands; those of exhalations escape from their
respective surfaces; those of nutrition remain in the organs.

It seems to me, that the explanation which exhibits nature always
pursuing an uniform course in her operations, drawing the same results
from the same principles, has a greater degree of probability than that
which shows her separating, as it were, this phenomenon from all the
others, in the way which she produces it.

The manner in which caloric enters the body, is of no consequence.
Vegetables that have no lungs, but only air tubes and absorbents,
and fishes that have branchiæ, have an independent temperature. That
heat may be produced, it is sufficient that foreign substances are
continually assimilated to the fluids of organized bodies, and that
after this assimilation, these fluids, whether they are blood, as in
animals with red blood, either warm or cold, or whether they are of a
different nature, as in those with white fluids and in plants, it is
sufficient, I say, that the fluids undergo different transformations in
the capillary system.

Respiration combines more caloric with the blood; there is consequently
a greater disengagement of this principle in animals who breathe by
lungs, than in others; and even in the first, the greater the lungs,
the greater is the quantity of caloric disengaged; as is proved by
comparing birds, quadrupeds, the cetaceous tribe among fishes, &c.
But these varieties are certainly only in relation to the degree of
temperature; hence there are animals with cold blood, and those with
warm. The general phenomena of the disengagement of heat remain always
the same in animals with lungs, in those without them, and in plants.

From these principles, it is easy to understand most of the phenomena
of animal heat.

The disengagement of caloric is always subordinate to the state of
the vital forces. As the tone of a part is greater or less, it is
more or less warm. This dependance of the heat upon the state of the
forces of the part, is a fact, that is proved by all diseases and
all the phenomena of health; it is as true with regard to heat, as
it is with regard to the exhalations and the secretions. The greater
afflux of blood to an inflamed part and the greater disengagement of
caloric, the increase of this disengagement in the womb and the nose,
and menstruation and the active nasal hemorrhages, &c. the heat of
the chest and active pulmonary hemorrhages, &c. are the effects of
the same cause, viz. the increase of the vital forces of the part. In
general, whenever the tone is much increased, the heat increases also;
hence why there is a greater disengagement of it in almost all active
sweats, hemorrhages, and even secretions; whilst this fluid is not
superabundant in sweats, hemorrhages, or secretions that are called
passive, whatever may be the quantity of fluid separated from the blood
by them.

Each system has its own degree of heat. There is certainly less caloric
given off in the hair, the nails, and the epidermis, than in the
other systems. The white organs, as the tendons, the aponeuroses, the
ligaments, the cartilages, &c. have probably less than the muscles.
Examine the claws of birds, in which there are only these white parts;
they are not so warm as the rest of the body.

The difference of the heat of each system situated in the interior
has not yet been analyzed; I am persuaded that if it was done with
precision, by insulating those which can be, so that they might
communicate by the vessels, we should observe that each separates a
different quantity of caloric, and that consequently there are as
many distinct temperatures in the general temperature, as there are
organized systems.

I am convinced that the ligaments, the cartilages, &c. approximate in
this respect the organs of animals with cold blood, and that if man
was composed of organs analogous to those, his temperature would be
much inferior to what it naturally is. The systems which disengage more
caloric communicate it to those that disengage less. If the hair was in
the middle of the body, it would be as warm as the neighbouring parts,
though its temperature would be independent; it is now always inferior
to that of the body, because it is insulated. Each system has then its
peculiar mode of heat, as each has its peculiar mode of secretion, each
exhalant surface its peculiar mode of exhalation, each texture its
peculiar mode of nutrition; and all this depends immediately on the
modifications that the vital properties have in each part.

It is in consequence of this peculiarity of heat in each system, that
each gives a different sensation in inflammation. Compare the sharp and
biting heat of erysipelas with that of phlegmon; certain dull, obscure
heats, the forerunners of organic affections, with the acute heats
of different inflammations; apply the hand to the skin in different
fevers, you will see that each is almost marked by a particular kind of
heat. Animal bodies alone exhibit these varieties of nature in heat;
minerals have only varieties in degree.

We understand from the principles explained above, not only the
local alterations of heat, but also the general derangement that
takes place in its disengagement, from the effect of diseases,
whether this disengagement is increased, diminished, or affected with
irregularities, as in certain ataxic fevers, in phthisis, when the
palms of the hands and the face are warmer in some cases, &c. Who does
not know that oftentimes when the extremities are frozen, the patient
feels an extraordinary internal heat? It is sufficient that the forces
of the capillary system be differently modified, that the heat may be
so also.

Observe, in fact, that the alterations of heat in diseases are as
frequent as those of the exhalations and secretions, and that they
always present, like the first, a previous derangement in the vital
forces. If chemists apply their theories to these morbid changes of
heat, instead of considering them as a necessary consequence of the
state in which the vital forces are then found, they will necessarily
find in them an insurmountable obstacle.

When we run swiftly, when the blood is violently agitated in the
paroxysm of fever, more caloric is disengaged than at any other time.
Does this prove that it is the general circulation which contributes
to the disengagement of caloric, and that it takes place in the great
vessels? No more than a copious sweat proves that the heart drives it
out. Strongly excited by the shock of the red blood which is suddenly
increased, the capillary and exhalant systems are compelled to
increase their action; now a double effect is the result; 1st, greater
disengagement of caloric; 2d, increased exhalation.

If the heat is increased when respiration is hurried, it appears to
depend only on this, that the latter is hardly ever accelerated,
without the circulation being so too. This is so true, that if you make
for a long time rapidly successive inspirations and expirations, the
heat will not increase. Besides, why should the heat actually increase
by the hurry of respiration? Undoubtedly because more air entering in
a given time, the lungs would absorb more oxygen, and consequently,
according to the opinions of the chemists, more caloric would be
disengaged. But let them present more or less of this principle to the
blood, it absorbs the same quantity. In ordinary inspiration the air
contains much more than can pass into this fluid. When an animal is
made to breathe it pure, the blood does not become more red, because
the same quantity always enters it. So you may in vain put into the
alimentary passages four times more nutritive substance than common, no
more chyle will be formed, the lacteals will absorb no more; there will
only be more excrements, or vomiting will take place.

The state of respiration has no influence then upon the actual heat of
the body; it only contributes to it by constantly introducing a greater
or less quantity of combined caloric. It is thus that animals which
respire the most, have habitually the most caloric.

How can an animal, breathing a very cold air, eating aliments almost
deprived of caloric, &c. in northern latitudes, have as much heat as in
hot climates? It is not the free caloric contained in the parts, but
the combined, which, being introduced into the blood with the foreign
substances, furnishes the materials of that which is disengaged in
the general capillary system. Now the combined caloric is absolutely
independent of temperature. As much fire is elicited from the same
stone by the steel, in the coldest as in the warmest countries.

All the caloric that is combined with the red blood is not disengaged
whilst this fluid is passing through the general capillary system;
there remains some of it still combined with the black blood. Hence
why in the first moments of asphyxia, before death has taken place,
though in consequence of the interruption of respiration, all the
blood that comes through the arteries to the capillaries is black, the
heat continues to be generated for some time. When the contact of the
black blood has even interrupted all the great functions, those of the
brain, of the muscles, the heart, the lungs, &c. it appears that the
black blood then undergoes for some time, a kind of oscillation in the
capillary system, by which it disengages a little caloric. Hence,
why those who have died of asphyxia produced by charcoal, or hanging,
animals killed in vacuo, apoplectics, &c. preserve their heat a long
time after death, as all physicians have observed.

This phenomenon is not however peculiar to the case of which we are
treating. In opening dead bodies at the Hotel Dieu, I have observed
that the time in which they lost their animal heat was very variable;
that a body continues warm a greater or less time, especially among
those who have died suddenly of an acute affection, in the paroxysm
of an ataxic fever, for example, or by a fall, for those who die of a
chronic disease, lose almost immediately their caloric. The difference
in the first is often three, four, or even six hours. This phenomenon
arises from the fact, that whenever death is sudden it interrupts only
the great functions; the tonic action of the parts continues for a
greater or less time after. Now this action disengages a little caloric
from the blood that is in the general system. Thus in violent deaths,
absorption continues some time after death; thus the muscles still
contract; thus perhaps the glands, take up for some hours, from the
blood that remains in the capillary system, the materials proper for
their secretion.

This inequality in the heat of dead bodies can only arise from the
cause I have named; for when the disengagement of caloric has ceased in
the body, that which remains in it becomes in equilibrium with that of
the external air, according to the general laws of this equilibrium.
Now these laws being uniform, their effect would be the same in
every case. Hence then the phenomena related above, are evidently
incompatible with any other theory than that which supposes the caloric
to be disengaged in the general capillary system.

Sympathy has, as we know, the greatest influence upon heat. According
as this or that part is affected, there is disengaged in others more
or less of their fluid. An icy coldness often takes place in syncope.
Ulcerations of the lungs produce a burning in the palms of the hands.
In other affections, the head seems to be the seat of the greatest
heat. In a fever frequently the patient is hot in one place and cold in
another. How does all this happen? in this way; the affected organ acts
sympathetically on the tonic forces of the part; these being raised,
more caloric than usual is disengaged; it is precisely the same as in
sympathetic secretions or exhalations. Whether the vital forces are
raised by a stimulus directly applied, or by the sympathetic influence
they receive, the effect that results from it is exactly the same.

It is necessary to distinguish this sympathetic increase of heat, from
those that are produced by an aberration of perception, as when we
think we are very hot or cold in a part, or experience even a sensation
exactly analogous to those that are natural, though the part to which
we refer this sensation may be in its natural state, there being
neither more or less caloric disengaged in it. It is as when we think
we feel pain in the amputated extremity of a limb. It is an aberration
of perception; it is truly a sympathy of animal sensibility, whereas
the preceding is a sympathy of insensible organic contractility or
tone. It is this last property that is affected; the disengagement of
caloric is a consequence; it takes place as usual, like the perception
that indicates its presence. Another person's hand applied on the
part, feels nothing new in the first case, of which I shall say more
in the following systems; it experiences a warmer sensation in this.
So if the effect of the sympathetic influence is to diminish the tonic
forces, there will be a less local disengagement of this fluid, which
will be equally perceptible to the individual and to any other person
who applies his hand to the part. Diseases continually furnish us with
examples of these phenomena in relation to heat, and no other theory
than the one now given would be able to explain them.

There is a phenomenon that is as difficult to be well understood by
this theory as any other; it is the faculty animals have of resisting
external heat. Every inert body is of the same temperature as the
medium which surrounds it. Every organized body on the contrary repels
the caloric that tends to raise it to a higher temperature than its
own. Perhaps this belongs to the laws of the propagation of caloric, of
which we are ignorant.

It will be asked undoubtedly why in the ordinary state there is only
disengaged a certain quantity of caloric, so as to produce an uniform
temperature of a certain number of degrees of the thermometer. I answer
that it is by the same cause that in the ordinary state the pulse
beats nearly the same number of times in a minute, which makes common
respiration consist of so many elevations and depressions of the ribs,
&c. &c. It is one of those phenomena that belongs to the immutable
order first established, and which it is impossible to explain. Only
it appears that this immutable order depends upon the primitive type
that has been impressed upon the vital forces, a type, which when
nothing excites or diminishes them, produces always phenomena nearly
uniform; but as a thousand causes make them vary, a thousand times
the pulse, respiration, heat, &c. are capable of differing. I would
observe however in regard to the last, that its variations are not so
great as those of many of the other functions. Compare, for example,
the ordinary quantity of secreted and exhaled fluids, with the increase
that takes place under certain circumstances, the common state of the
pulse with its exacerbations in many fevers, &c. you will see that
between the natural and the morbid state there is often an enormous
difference. The heat on the contrary, is never raised but a few degrees
above the temperature of the body. When there appears by touching the
parts, to be a great difference, the thermometer proves that it is in
reality trifling.

I would remark, in concluding this article, that I have not sought
to ascertain how the caloric is disengaged in the capillary system,
what portion escapes, in what relation it is with the red and the
black blood, &c.; none of these can be determined by experiment. Let
us be content in our theories with establishing general principles,
especially analogies between functions that are known, and those
which we attempt to explain, let us attempt merely to offer some
general views; but let us never hazard precise explanations. Some have
endeavoured lately to determine accurately what quantity of oxygen
is absorbed, what quantity goes to produce the water of respiration,
what quantity of carbonic acid gas is formed, how much caloric is
disengaged, &c. This precision would be advantageous if it could be
attained; but no phenomenon in the living economy will admit of it, in
the explanations which it occasions. Chemists and natural philosophers
accustomed to study the phenomena over which the physical forces
preside, have carried their spirit of calculation into the theories
they have formed for those which the vital laws govern. But this should
not be so. In organized bodies, the spirit of the theories should
be wholly different from the spirit of the theories applied to the
physical sciences. It is necessary in these last that every phenomenon
should be accurately explained; that, for example, in hydraulics, all
the portions of the fluids should be calculated in their motions; that,
in chemistry, we should know the precise proportion and amount of each
of the elements that are combined in the changes that bodies undergo.

On the contrary, every physiological explanation should give only
general views, approximations; it ought to be vague, if I may use the
term. Every calculation, every examination of the proportions of the
fluids with each other, all precise language should be banished from
it, because we yet know so little of the vital laws, they are subject
to so many variations, that what is true at the moment we study a fact,
ceases to be so the next, and the essence of the phenomena always
escapes us; their general results only, and the comparison of these
results with each other, should occupy us.


ARTICLE SECOND.

PULMONARY CAPILLARY SYSTEM.

I call by this name the assemblage of the fine and delicate
ramifications, which serve for the termination of the black blood and
the origin of the red, which consequently finish the pulmonary artery
and give origin to the pulmonary veins. The capillaries between the
bronchial arteries and veins have nothing to do with them, they have no
communication, and evidently belong to the general capillary system.


I. _Relation of the two Capillary Systems, Pulmonary and General._

In comparing the preceding system with this, it is difficult to
understand how they can exactly correspond, how the pulmonary can
transmit not only all that passes through the general, but also all the
lymph that returns from the serous surfaces and the cellular cavities,
all the chyle which enters by digestion, &c. &c.

It seems impossible at first view, that in the balance of the
circulation, these capillaries can, constantly and regularly, keep
in equilibrium with those of the rest of the body. By reflecting a
little, however, upon the phenomena of this function, we see that the
discordance is only apparent.

Though the general capillary system is everywhere spread out, yet the
portion in which blood circulates is much more limited than at first
appears. There is a great part of the vessels of this system, in
which fluids differing from the blood move and oscillate in different
directions. Then, where the blood especially enters, as in the muscles,
the mucous surfaces, &c. a considerable portion of this fluid, its
colouring matter particularly, is in a combined state, and not in a
state of circulation. If we cut a muscle transversely in a living
animal, inspection proves clearly this phenomenon, which, joined to the
preceding, diminishes immediately more than half the blood, which at
first appears to move in the general capillary system.

Yet it is evident, that there remains much more of it constantly in
this system than in the pulmonary; to be convinced of this, it is
only necessary to cut the lungs of a living animal. From this it is
clear, that if the heart presided over the motion of the blood in the
general system, and that consequently all that is contained in it was
driven into the veins at each pulsation, the pulmonary capillaries
would be insufficient to transmit it; but there goes out only a certain
quantity, proportioned to what the lungs can receive. It is nearly
the same as when the veins are much dilated, and consequently contain
much blood; no more arrives at the heart, because, as I have said, the
velocity is then in the inverse ratio of the capacity.

Besides, many causes continually divert the blood of the general
capillary system from the direction which carries it from the arteries
to the veins; these causes are especially the exhalations, secretions,
and nutrition. This capillary system is, as I have observed, a common
reservoir, whence the blood is carried into different and even opposite
directions, on one part in the direction of the veins, on another in
that of the exhalants, on another in that of the excretories, on
another, in fine, in that of the nutritive vessels. On the contrary,
in the pulmonary capillary system, there is but a single impulse, and
a single direction; it is that which carries the blood from the artery
to the pulmonary veins, which nothing draws off in its course; for in
passing from the black to the red, this fluid serves no other function;
it has no vessels, but the pulmonary veins, towards which its motion
is directed. There is, then, this great difference in the blood of the
pulmonary capillaries, and that of all the other parts, viz. that the
first is moved only in one direction, that all which arrives in the
lungs goes immediately in this direction; whereas the second has four
or five different directions. Hence this last necessarily oscillates
and varies in its motions, according as it is called more or less
powerfully by the exhalants, the excretories, the nourishing vessels,
or the veins; whereas the other, having but one way to escape, follows
it constantly and uniformly. Let us not be astonished, then, at the
disproportion there is in the capacity of the two capillary systems.

The proximity and distance of the heart are also a real cause that
tends to establish the equilibrium between the two systems. We have
seen, in fact, that each contraction of the left ventricle impresses a
sudden motion upon the whole mass of blood contained in the arteries,
and at the instant that this mass increases on one side, it is
diminished on the other by the quantity that is sent to the capillaries
of the whole body; so that the arterial motion is not progressive,
but sudden and instantaneous, so that at the same time the column of
aortic blood increases towards the heart, it diminishes in its remote
ramifications, and the fluid driven from the heart at each contraction,
does not arrive at the capillaries until after many contractions, since
that which goes from this organ cannot arrive at these vessels until
all which is before it has reached them. The same phenomenon precisely
takes place as it respects the black blood in the pulmonary artery.
Then the longer the course, the longer is the time that is required
for the blood to arrive at the capillaries, and consequently to pass
through them; then the blood from the right ventricle would arrive much
sooner at the left auricle, than that would at the right auricle which
goes from the left ventricle; then, though in what we call the small
circulation, the velocity is not greater, the space passed over being
less, the time employed to go over it is also less; then, the excess
of the fluid contained in the divisions of the aorta, in the general
capillary system, and in the general veins, over that contained in the
pulmonary artery, veins and capillary system, is compensated by the
time the second takes to go its course, which is short in comparison to
that of the first.

Hence we see, why in animals in whom the lungs, as to their
circulation, are in opposition to the rest of the body, nature has
constantly placed this organ at the side of the heart. If one of these
organs was at the head, and the other at the bottom of the pelvis, the
harmony would be inevitably interrupted.


II. _Remarks upon the Circulation of the Pulmonary Capillaries._

Since the blood of all the parts constantly goes through the lungs, it
is evident that an injury of the functions of this viscus would be felt
in all the parts. The phenomena of asphyxia prove that this in fact
takes place. It is in this way that the lungs are immediately connected
with life, and hence the ancient physicians placed its functions among
those which they called vital.

We understand also why pulmonary inflammations have so peculiar a
character; why they are distinguished from others by many phenomena.
No internal organ is more often inflamed than the lungs. If experience
did not prove this at the bed-side of the patient, the examination of
dead bodies would be sufficient to convince us of it. We find in fact
around the lungs, very often traces of old inflammations, particularly
adhesions of the pleura; a phenomenon so common, that I am confident
that there are more dead bodies found with it, than there are without
it. This is an essential difference of this membrane that distinguishes
it from all analogous ones, a difference that arises from the proximity
of the pleura to the organ that it covers. Different causes contribute
to this very great frequency of pulmonary inflammations. 1st. The lungs
are, among the internal organs, the most exposed to direct irritations,
either by the air that constantly enters them and can irritate them,
or by heterogeneous substances that it introduces, or especially by
the changes of heat and cold that it occasions. 2d. These organs are
connected by the most numerous sympathies with the other systems, the
cutaneous, for example; so that perhaps, as it respects inflammation,
a suppression of transpiration has as much influence upon the lungs
alone, as upon all the other organs together. It depends no doubt upon
this that the lungs correspond with all the others by their capillaries.

When the lungs are inflamed, is it the red blood of the bronchial
artery that flows to the irritated place, or the black blood of the
pulmonary artery? I think that it is difficult to decide this question
by experiment; but examination after death appears to prove that the
second performs an important part in it. In fact, this viscus is often
crowded so suddenly, that we can hardly believe that the first would be
able to furnish the blood. Sometimes, though it is not always the case,
we can trace as it were, the progress of this crowding by percussion,
which is infinitely less sonorous in the evening than the morning.
There died a short time since a patient under my care in the hospital,
in whom this difference was perceptible from hour to hour. The progress
is much less rapid, no doubt, in the greatest number of cases; but in
those the black blood has undoubtedly contributed to the crowding of
the lungs.

No organ in the animal economy acquires by inflammation, so great a
size in so short a time, and such excessive weight, as the lungs.
All who open dead bodies know this. Observe the lungs of one dead
of pneumonia; cut them, and you would say at first that they were
solid; they often look like liver, they exhibit the appearance of such
a heavy mass; but macerate them and soon the whole will escape in
fluids. Now examine comparatively the skin, the stomach, the liver,
the kidnies, &c. when they have been the seat of acute inflammation,
that has destroyed the patient; they have nothing approaching to this
enormous increase of fluid, which is seen in the substance of inflamed
lungs. Not only the cavity of the cells is full, but the organ is
also much dilated. I have often had occasion to open those who have
died of pneumonia, in whom one of the lungs was entirely sound; now,
the disproportion of weight between it and the affected one, was
incomparably greater than that between an inflamed kidney and a sound
one.

This phenomenon evidently arises from the fact, that the lungs alone
receive as much blood as the whole body, so that when an inflammation
of this viscus interrupts the course of the fluids, a very great
quantity of them can accumulate there in a given time. It is not
however, properly speaking, the blood that is found crowding the lungs
in pneumonia; the fluid appears whitish when pressed out; we should
say that it was a kind of pus. Much has been said of vomicæ after
pneumonia; but they are extremely rare; there is almost always effusion
in the lungs; the fluid is not collected in a sac.

In pulmonary inflammation, does the blood pass through vessels that do
not ordinarily circulate it, as happens so evidently upon the serous
surfaces, or conjunctiva, &c. when inflamed? I do not think it does,
for we do not know any vessels in the lungs, except the sanguineous.
It appears evident that the blood or the other fluids are effused into
the pulmonary texture, in which they are deposited by exhalation. There
is no doubt that in some phlegmons, this fluid passes, as I shall
say, into the cells of the cellular texture; now it appears that it
happens here in the same way. By breaking or cutting inflamed lungs,
we see clearly that its whole texture is crowded, and filled; whereas
in examining an inflamed serous surface, we see that the blood is
evidently contained in the capillaries.

It is a great mistake to try to represent inflammation as being
everywhere the same, as exhibiting always the fluids, like their
vessels, in the same state. Boerhaave for example thought, that there
could be no inflammation without an _error loci_. There is according
to the state of the parts, their structure, their vital properties, a
thousand different modifications in the new anatomical order that this
affection gives to the organs.

What constitutes the essence of inflammation is, 1st, the irritation of
the inflamed part; 2d, the new modifications that its vital forces have
taken in consequence of that irritation; 3d, the consequent stagnation
of the fluids around it. But in what manner the fluids are arrested;
how they stop in the capillary system; how they are taken up by the
exhalants; how they are poured out, in extravasations, &c.; these are
different effects that arise from the different organization of the
parts; but the principle is always the same, it is always the same
disease. If we could analyze thoroughly the state of all the systems in
inflammation, we should see perhaps, that there was a difference in the
inflammation of each. Besides, the diversity of the symptoms that it
exhibits, a diversity of which I have already spoken, proves that the
state of the solids and the fluids are not the same.

How is it that the blood can pass through the lungs of phthisical
patients, in whom this organ is reduced nearly one half? I would
observe upon this subject, that the blood in the great vessels is
diminished in proportion to the ulceration of the lungs. The diminution
of this fluid is remarkable in many organic affections, but especially
in these, as Portal has observed. If a phthisical patient in the
last stage had as much blood, as before the disease, the circulation
certainly could not go on, or at least there would be a constant reflux
towards the right auricle. Who is ignorant of the small pulse, feeble
though frequent, particularly towards night, in phthisis? Compare it
with the pulse of an inflammatory fever, in which there is evidently
plethora; you will see that they are really the two extremes.

I will make a general observation upon this subject, it is this, that
when the forces are weakened in our organs, or life languishes in them,
the blood is diminished almost continually in proportion; so that this
fluid being considered in the capillary system, as the resistance
opposed to the power of the small vessels, the proportion remains
always the same between this power and this resistance. It is necessary
that the whole should be in relation. If blood was transfused into a
phthisical patient, he would die, because the forces of the solids
would not correspond with the increase of action to which they would be
forced.

The circulation of the pulmonary capillaries, is, like that of the
others, under the influence of the tonic forces of the part, and not
under that of the impulse of the heart. This impulse terminates at the
extremity of the branches of the pulmonary artery. In inflammation then
of the lungs, the blood is not mechanically arrested in this organ;
then, when you bleed, it is not to diminish the _vis à tergo_. You
might draw ten basins from the patient, but the lungs most commonly
would not empty themselves; they would be less fatigued by the
entrance of the blood; but that which was stagnant in the capillary
system would still remain there. So long as there is a point of
irritation, it will be, if we may so say, a magnet which will attract
the blood, and completely change its direction; which was before from
the artery to the veins, it will now be only towards the irritated
point. Bleeding acts then, 1st, by diminishing the blood that enters
the lungs, and consequently by lessening the fatigue of this diseased
organ; 2d, by diminishing the irritation of the solid, which attracts
the blood, and retains it around the irritated place.

The constant excitement that the air gives to the pulmonary capillary
system is favourable to its circulation; but the blood can traverse
this system without this excitement, as is proved by my experiments
mentioned elsewhere.


III. _Alteration of the Blood in the Pulmonary Capillaries._

There takes place here the reverse of what happens in the general
capillaries; the fluid changes from black to red. We have already some
data upon the causes of this phenomenon; but I think new experiments
should be made before a thorough explanation can be given. This is so
much the more necessary, because if we knew how the black blood becomes
red, it would seem that we might know how the red becomes black.

I have stated the phenomena of this change of colour in my work upon
Life and Death; it would be superfluous to repeat them. There will be
found there also many details upon the circulation of the two capillary
systems, which I shall not mention here.


IV. _Remarks upon the state of the Lungs in Dead Bodies._

I will only corroborate here a remark already made in the same work,
upon the extreme frequency of pulmonary congestions in the last moments
of life. As the lungs alone receive the whole blood of the body,
when their forces are weakened, the blood stagnates and accumulates
in them; so that according to the state of their forces in the last
moments, and the disease, these organs will be more or less heavy,
and more or less full of blood. We hardly find them twice in the same
state. All subjects that die in pain have these congestions. Thus
compare the lungs of dead bodies in our dissecting rooms, with those
of animals killed in slaughter-houses; they are entirely different.
The organization is almost always concealed in the first by the fluids
that crowd them. We cannot study this organization well except in
subjects that have died of hemorrhage or syncope. In most others, it
is impossible to distinguish any thing. Hence no doubt the reason that
we know as yet so little of the intimate structure of this important
viscus, as the description I shall give of it will, I hope, prove. I
have shown elsewhere how we can at will accumulate a greater or less
quantity of blood in the lungs of an animal, by the way in which we
kill him.

No other organ in the economy exhibits these extreme varieties of
congestion at the moment of death, in so evident a manner at least,
because no one is a centre of circulation, like the lungs; the liver
even is not an exception, as I have observed. In this respect, those
who open dead bodies, and examine the state of the lungs, should
carefully distinguish the congestion that arises from the disease,
from that which may be perhaps the effect of the interruption of the
circulation in the last moments. I suppose two affections of the chest
exactly similar in their nature, duration and the two subjects they
attack; that syncope terminates the life of one of them; that that of
the other is closed after long distress, in which there is what is
called the rattles; the lungs of the second will certainly weigh much
more than those of the first.

It is very probable that during life, the lungs are in very different
degrees of congestion. We know that most chronic diseases of this organ
occasion, when the patients take rather violent exercise, a sense of
suffocation, oppression, &c. which appear to be owing only to the
superabundance of blood, which, not being able to pass through this
viscus as fast as it is sent there, is stopt, and checks the entrance
and exit of the air.

It is only the diseases of the lungs and heart that are accompanied
constantly with these oppressions, and sense of suffocation. This is
seen in this last organ in aneurisms, sometimes in ossifications, &c.



EXHALANT SYSTEM.


Exhalation and secretion are two functions, analogous in this, that
both of them separate from the blood fluids differing from it, and pour
them upon surfaces where they serve different uses. But the following
are their differences.

1st. In exhalation, there is no intermediate organ between the arteries
and the exhalants; a capillary net-work alone separates them; whilst
on the contrary there is always an intermediate organ between the
excretories and the arteries; it is in this organ that the capillaries
are found, in which the second begin and the first terminate. 2d.
The organized machines which elaborate the secreted fluids are then
much more complicated than those which separate the exhaled fluids.
Thus the bile, the urine, the saliva, &c. differ on the one hand
essentially from the blood, and are on the other much compounded;
whilst the serum, &c. closely resembles some parts of the blood, and
is but slightly compounded, containing but few elements. This double
distinctive character of the two kinds of fluids appears to me to be
very striking. 3d. The exhaled fluids are poured out by an infinity
of small tubes separate from each other; the secreted fluids, on the
contrary, are collected in one or more principal tubes that pour them
on the surface where they terminate. 4th. The exhaled fluids re-enter
in great part into the circulation, after having been thrown out; the
secreted fluids, on the contrary, appear to be especially destined
to be rejected. 5th. Many parts receive the first fluids; they are
deposited upon the serous, mucous, synovial and cutaneous surfaces,
in the cellular texture and even in all the organs of nutrition. The
mucous and cutaneous surfaces, the first especially, are the only ones
upon which the others are poured out.

It follows from all these considerations, that the exhaled fluids, as
the fat, the serum, the synovia, the marrow, &c. differ essentially
from the secreted fluids, as the bile, the urine, the saliva, the
mucous, prostate, spermatic, pancreatic fluids, &c. This difference
appears to have struck a great number of authors; yet most of them
have made use of the term secretion to express the separation of
the exhaled fluids from the mass of blood. I think that there is
much analogy between exhalation and secretion. In both, there is the
capillary system, as I have said, between the vessel that brings and
that which carries away; but the capillary system is certainly arranged
very differently in a gland, from what it is in a serous surface; for
example, wherever there is exhalation, there is certainly nothing but
the capillary system; but where there is secretion, the secretory
organ is too considerable not to admit of something more. Besides, by
trusting to inspection, and without wishing to examine the intimate
nature of the organs, it is evident that where there is secretion,
there is a gland, and that this gland is wanting where there is
exhalation.


ARTICLE FIRST.

GENERAL ARRANGEMENT OF THE EXHALANTS.


I. _Origin, course, and termination._

Authors have formed very different ideas concerning the exhalants.
We know the decreasing vessels of Boerhaave, and the error loci for
which his imagination created these vessels. Lately all the white
vessels continuous with the arteries have been rejected, and in order
to explain exhalation, recourse has been had only to inorganic pores
in the arterial parietes, through which the fluids transude upon the
organs. Frequent observation of similar transudations upon the dead
body, as those of the bile through the gall-bladder, of the marrow
through the osseous texture which it discolours, &c. is one of the
great supports of this method of explaining the exhalant system. But
we have already many times observed, that these phenomena never take
place during life, when the organic sensibility of the parts refuses
to produce them. Besides, exhalation is evidently subjected to the
influence of the vital forces, since it varies continually in a part,
according as the vital forces of the part themselves vary. Moreover,
if the exhaled fluids escaped through inorganic pores, it would be
necessary that not only the vascular parietes, but also those of the
serous surfaces which receive these fluids, should be perforated
with small holes; why then would not these fluids, of which these
surfaces are the reservoirs, transude into the neighbouring cellular
texture? Let us reject then every opinion that disregards anatomical
observation, and let us endeavour by this observation to ascertain what
the exhalants are.

It is undoubtedly difficult to form a precise idea of these vessels,
their extreme tenuity constantly conceals them from us in a natural
state. Yet by the aid of experiments and accurate reasoning, it
appears to me that we may come at some degree of accuracy.

We have seen that the existence of a capillary system terminating
the arteries, is in the parts where exhalation takes place as in the
others, a thing incontestably proved by experiment with injections, by
inflammations which arise spontaneously, and by those that are produced
at will; so that a serous, cutaneous surface, &c. on which nothing
appears, is covered with an infinity of little vessels suddenly in the
first case, and at the end of a longer or shorter time in the second.

If the injection is not pushed very far, it is confined to the
capillary system; but if it succeeds, it pours from all parts upon
the surface, where exhalation takes place in the ordinary state. This
dew mechanically produced, evidently resembles that which the tonic
force of the parts occasions during life; for, as I have said, if it
was a transudation, there would be extravasation in the neighbouring
textures, whereas nothing is filled from the syringe which propels
the injection to the exhalants that pour it out, except the arteries,
the capillaries and these exhalants. Besides, when there is active
hemorrhage, the capillaries from which arise the exhalants that pour
out the blood, are evidently more full of fluid than ordinary, as I
have already remarked.

From these considerations and many others that will be explained
hereafter in this system, I think that we may consider the exhalants as
arising from the capillary system, by means of which they are continued
with the arteries, which bring them the materials of exhalation.

But to say what is the length of these vessels, what their form, what
course they run, is evidently impossible; it is here that the imaginary
descriptions begin. We distinguish with difficulty their orifices. We
see upon the skin many little pores that evidently form communications
from within to without; but these pores transmit not only the
exhalants, but also the absorbents, the hair, &c. as we shall see in
the dermoid system. 1st. The existence of the exhalants; 2d, their
origin in the capillary system of the part where they are found; 3d,
their termination upon different surfaces, are upon the whole all that
is accurately known.

The mode of origin undoubtedly varies, but we do not know how it takes
place. The exhalants are continued with their capillary net-work, in
such a manner that we cannot say precisely where one finishes and
the others begin. Hence why often in this work, in speaking of these
small tubes, I suppose them to come immediately from the arteries,
and forming the capillaries by their interlacing; this is evidently
sufficient to understand what will be said hereafter.


II. _Division of the Exhalants._

There are three classes of exhalants which I distinguish by the fluids
or the substances they furnish.

The first class contains those that throw out the fluids not destined
to enter the economy again; such are, 1st, the cutaneous exhalants that
pour out the sweat; 2d, the mucous exhalants that furnish a part of the
pulmonary perspiration, the greatest part being formed, as I shall say,
by the dissolution of the mucous fluids of respiration, which yield
perhaps the gastric, intestinal juices, &c.

In the second class are found the exhalants, that throw out fluids
that remain for some time upon certain surfaces or in certain cells;
and which afterwards taken up by absorption, re-enter the circulation
through the lymphatics. These are, 1st, the serous exhalants which
deposit upon their respective surfaces the serum which lubricates the
membranes and facilitates the motions of the organs they cover; 2d,
the cellular exhalants which pour out into the cells, on the one part
serum, on the other fat; 3d, the medullary exhalants which carry into
the middle of the bones the juices of the same name; 4th, the synovial
exhalants which deposit the synovia, either upon the articulations, or
in the tendinous grooves.

The third class contains the exhalants that carry to all the organs the
nutritive substance that repairs them, and which is afterwards taken up
by absorption, to be replaced by new substances.

I adopt in my course of physiology the division I have just pointed
out, to explain the different exhalations, of which the last evidently
leads me to speak of nutrition, a function which is the general end of
those that form organic life. We can represent in the following table,
all the different exhalations; it presents the assemblage of the organs
that execute them.

            ┌1st. exterior,  ┌1st. Dermoid.
            │ open upon      │
            │ the systems,   └2d. Mucous.
            │                ┌1st Serous.
            │                │2d. Cellular, ┌1st. Serum.
            │                │ where they   │
  EXHALANTS.│                │ pour out,    └2d. Fat.
            │2d. interior,   │              ┌1st. of the short, flat
            │ open upon      │3d Medullary. │ bones, and the extremities
            │ the systems,   │              │ of the long ones.
            │                │              │2d. of the middle of the
            │                │              └ long bones.
            │                │
            │                │              ┌1st. of the articulations.
            │                └4th. Synovial.└2d. of the tendons.
            │
            └3d. nutritive.   Each organized texture has its own
                               exhalants.

This is an accurate table of all the fluids that go out of the blood,
without the intervention of the glands, and by the way of exhalation.
The two first classes have vessels, as is accurately proved by
experiment, observation and even inspection. As to the nutritive
exhalants, there is no doubt but that new substances are continually
carried to the organs to repair them; now it is necessary that these
substances should have vessels; these vessels certainly cannot draw
what they deposit in them, except from the capillary system in which
they terminate. If injections or other means do not accurately prove
the existence of these exhalants, it seems to me that this reasoning
forces us to admit them.

Physiologists had not hitherto collected together all the exhalations;
each was explained in treating of the system where it was found. I have
thus given reflections upon each in the exposition of the different
textures; the arrangement of the general anatomy required it; but
in works or in lectures on physiology, they ought evidently to be
presented under the same point of view as absorptions.


III. _Difference of the Exhalations._

Though we know not what is the structure of the exhalants, yet we
cannot doubt but that this structure differs remarkably in the
different systems. Observe in fact that these vessels enter, as
it were, like elements into the textures they compose, and that
consequently they must necessarily partake of the different and
distinctive characters which these textures exhibit.

It is to this difference that we must refer without doubt what we see
in injections. They go out, if they are fine, by the mucous, serous and
even cellular exhalants; but those which furnish the synovia, transmit
them with much more difficulty; it is the same in the capillary system;
whilst the serous surfaces in this system are filled with great ease,
and blackened by injections, as it were at will, the synovial surfaces
are penetrated with much more difficulty.


ARTICLE SECOND.

PROPERTIES, FUNCTIONS, AND DEVELOPMENT OF THE EXHALANT SYSTEM.


I. _Properties._

The vessels of the exhalant system are too delicate to allow us to
analyze their properties of texture. Do they enlarge when the red
globules enter them? I am wholly ignorant. Haller, who admitted that
there were exhalants, thought that white fluids alone entered them,
because their diameter was disproportioned to that of the red globules.
This opinion is also that of the school of Boerhaave. Who has ever
measured comparatively the respective diameters of the vessels and the
particles of the fluids? All such expressions, as fine fluids, coarse
fluids, &c. which are still used by many physicians, have originated
from this theory and are still used, though the theory itself has been
admitted to be false. I have said twenty times, and I again repeat it,
that the only cause which prevents the red globules from passing into
vessels with white fluids, is the want of relation between the nature
of the fluid and the sensibility of the organ.

The properties of animal life have evidently no connexion with
the exhalants. Of those of organic life, they have in the highest
degree those of organic sensibility and the corresponding insensible
contractility; it is upon these that all their functions depend.


_Characters of the Vital Properties._

Though organic sensibility is everywhere given to the exhalants, it
varies however remarkably in each system; that of the mucous exhalants
is not the same as that of the serous. In general the exhalants
entering as it were like elements into the texture of each system,
partake completely of the organic properties of that system; or rather
their properties are the same. Hence, 1st, why each separates the
fluid that is peculiar to it; why consequently, when much water is
introduced into the circulation by drinking, the cutaneous exhalants,
and never the serous, appropriate it to themselves, and transmit it out
of the blood; when we run much and a general agitation is consequently
given by the heart to the mass of blood in circulation, the cutaneous
exhalants, being more powerfully excited by this impression than the
serous, the synovial, &c. separate more sweat; 2d, why the serous do
not pour out fat, the medullary serum, &c. though the mass of blood
that enters the capillaries that are continuous with these exhalants,
is everywhere the same; 3d, why when the exhalants pour out fluids that
they are not accustomed to, or when their natural fluids are altered,
these fluids differ essentially from each other; why, for example,
after inflammation, it is only upon the serous surfaces that we see
a milky serum; why nothing resembling pus flows from the inflamed
medullary membrane; why the fluids, the result of the inflammation
of the synovial membranes, are very different from those that the
serous surfaces produce, &c.; 4th, why certain exhalants have a much
greater tendency than others to admit blood and pour it out upon
their respective surfaces, of which we see an example in the mucous
exhalants, which are so disposed to suffer this fluid to pass, that a
thousand circumstances occasion hemorrhages from them; 5th, why among
the mucous exhalants themselves, some have a much greater tendency than
other to permit the blood to pass, &c. &c.

All these phenomena are evidently derived from the particular
modifications that distinguish the organic sensibility and
contractility in each kind of exhalants.


II. _Of Natural Exhalations._

What I have said will enable us to explain how exhalation is effected.
It is by the same principle as that to which we have before referred;
it is that which will serve for the explanation of secretions,
absorptions, &c. There is between the elements which form each exhaled
fluid and the organic sensibility of each kind of exhalants, such a
relation, that these elements alone can be admitted by the vessels
which reject the others, so long as there is no change in their kind of
sensibility. The general capillary system appears to be the reservoir,
in which, as I have said, the blood is elaborated; it is there that
the red blood becomes black; it is there at the same time that its
different elements are separated, combine anew, and during these
changes disengage caloric. It is after these changes, these different
transformations, that each exhalant takes, chooses as it were the
portions with which its sensibility is in relation, and leaves the
others.

It follows hence as a very simple consequence, that whenever the
organic sensibility of the system in which exhalation takes place
is altered in any manner, exhalation should also immediately vary;
and this in fact always happens. There is never any derangement in
the exhalations, without a preceding one in the sensibility of the
exhalants. Take for example the different injuries of transpiration;
you will see that cold, heat, dryness, moisture, frictions, &c. always
exert their influence upon the cutaneous sensibility, and that the
derangements of the exhalation are consequent to them.

The organic sensibility of the exhalants, like that of every other
part, may be disordered in different ways, 1st, by a direct stimulant,
as when cold contracts the skin, when a very cold fluid acts upon
the stomach, &c.; 2d, by sympathies, as when the acute affection of
the fibrous and muscular organs produces sweat in rheumatism; 3d,
oftentimes without our being able to say how, a derangement takes place
in the vital forces of a part; of this inflammation presents frequent
examples. I do not allude here to that which takes place from the
contiguity of organs, &c. &c.

It follows from this, that when exhalation is preternaturally increased
or diminished, the sensibility of the exhalants is always modified in
one of the three preceding ways.

Now if we reflect upon the different kinds of exhalants, we shall see
that there are no others except the cutaneous and the mucous which are
exposed to the immediate application of stimuli, since they alone are
in relation with external bodies. Besides the two modes of alteration
of sensibility that they share with others, they have moreover this.
It is not then astonishing, that their exhalations, especially
the cutaneous, exhibit such numerous varieties, that the skin is
continually found varying between the greatest dryness and the most
copious sweat.

The sympathetic exhalations are extremely numerous. I shall not give
examples of them here; many may be found in the sympathies of the
dermoid, serous, mucous systems, &c. I would only observe that authors
have not sufficiently distinguished this kind of exhalations from
the others; nor has sufficient attention been paid to sympathetic
secretions.

The exhalations are never all increased or diminished at the same
time; I except however the state of excitement at the commencement
of some fevers, when all are suppressed. In every other case, when
one fluid is abundantly poured out, the others are diminished; thus
the skin is dry in dropsies. There is sweating in the first stages of
phthisis pulmonalis; but when in the latter, dropsical effusions are
considerable, sweating ceases.

I have moreover divided into two classes the causes of increased
exhalations. 1st, One of these proves an increase of life; 2d, the
other, a real diminution of the vital forces; hence active and passive
exhalations. How can the same phenomenon arise from two causes exactly
opposite? It is difficult to determine precisely; but so many phenomena
prove this distinction of exhalations as well as secretions, that we
cannot refuse to admit it. It is important to recollect this in the
following article.


III. _Of Preternatural Exhalations._

I call by this name those, in which the exhalants pour out a fluid
different from that which is natural to them. The first which offers is
that of the blood.


_Sanguineous Exhalation._

The blood frequently passes off by the exhalants instead of their own
fluids; hence arise hemorrhages very different from those that take
place from rupture. I shall examine these hemorrhages in each kind of
exhalants.


_Hemorrhage of the Excrementitious Exhalants._

The vulgar expression which is sometimes used, to sweat blood and
water, &c. indicates that under certain circumstances, though they
are very rare, the cutaneous exhalants give passage to the blood.
Haller has collected a number of instances of it, that may be found in
his work. The first year that I came to Paris, I saw constantly with
Desault, a woman with a cancer of the womb, who had at certain periods
sweats that stained her clothes as much as is ordinarily done by the
catamenia. This woman had had frequent hemorrhages before the beginning
of her disease. After these sweats commenced, they had continued but
were more rare. I regret that I neglected to collect the particulars of
this singular fact.

No exhalants pour out blood more frequently than the mucous; so that
hemorrhages are an affection almost characteristic of the mucous
surfaces, in which they have different names, according to the portion
of them that are attacked. It is not my object to present here the
phenomena of these hemorrhages; I only wish to prove that they are an
exhalation.

1st. I have very often opened subjects that have died during a
hemorrhage; I have had occasion to examine with this view the
bronchial, gastric, intestinal and uterine surfaces; I have never
seen the least mark of erosion, notwithstanding the precaution of
carefully washing the surfaces, of letting them macerate and even
examining them with a glass. 2d. The following experiment uniformly
succeeds upon the wombs of women who have died during menstruation,
and often even at other times; by pressing them, there issues from the
mucous surface a greater or less number of little bloody drops, which
evidently correspond with vascular extremities, and being wiped off,
no erosion can be seen. 3d. The analogy of all the other open surfaces
that pour out blood, and which evidently do it by their exhalants,
is a proof that the same phenomenon has the same seat in the mucous
surfaces. 4th. The womb would be only a mass of cicatrices in females
of advanced age, if there had been a rupture in it in menstruation.
5th. In active hemorrhages, in which there is evidently a congestion of
blood previous to its escape, we can conceive, to a certain degree of
the rupture of the small vessels; but in passive hemorrhages, in those
in which the organic sensibility being annihilated, seems to allow of
a simple transudation through the exhalants, how can we conceive of
these ruptures? 6th. We understand with difficulty how an evacuation,
which is often produced with an extreme rapidity, which ceases in one
place and immediately appears in another, which is subjected to all
the sympathetic influences, we understand, I say, with difficulty how
it can happen from rupture. 7th. Observe menstruation, furnishing
sometimes for one moment blood, and not giving it the next, renewing
twenty or thirty times a day, in certain affections, these alterations
of flowing and ceasing to flow; it would be necessary then, that at
each time the wounds should open and be cicatrized. 8th. Besides,
compare hemorrhages evidently produced by rupture upon the mucous
surfaces, such as those, which in wounds of the head, take place from
the nostrils, the ears, &c.; those, which by a fall upon the rectum,
sometimes happen from the bladder; those which, in too great efforts in
coughing, arise upon the bronchial surface; those of which the stomach
is the seat from the action of different poisons, &c. &c.; compare, I
say, these hemorrhages, and many analogous ones that I could mention,
with those that take place spontaneously from the mucous surfaces; you
will see that they do not resemble them in their phenomena and their
duration; that by suppressing them, they do not give rise to others;
that they are independent of all kinds of sympathetic influence; that
the passions have no effect upon their cessation or their production,
whilst they have so powerful an influence upon the others.

Let us conclude from all these considerations, that all mucous
hemorrhages, whether active or passive, are real exhalations. Hence
you see that there is not so great a difference as might be thought,
between the first and inflammation. In fact, in one there is an
accumulation of blood in the capillary system, then the passage of this
fluid by the exhalant vessels, that are continuous with this system. In
the other, there is only the first phenomenon. Undoubtedly the signs,
the circumstances, &c. are wholly different, because the modifications
the organic sensibility undergoes are not the same; but the state in
which the small vessels and the blood are respectively found, is not
less analogous. One proof that in active hemorrhages, it is the organic
sensibility which, differently modified, opens or closes the passage
to the blood by the exhalants, is this, that almost always there are
previous symptoms which continue for some time, and which evidently
declare the disturbance that the vital forces, the organic sensibility
in particular, experience in the part; we know the itching, the
forerunner of nasal hemorrhages, the tickling and sometimes sense
of heat which precede the pectoral. Sometimes, according to the
varieties of alteration it undergoes, the organic sensibility at first
permits serous fluids to pass, then bloody; this is what we see in
menstruation, in which the exhalants oftentimes pour out serum for some
minutes, then true blood.

In passive hemorrhages, the organic sensibility is without doubt
diminished, as well as the tone or insensible organic contractility.
We might say, that the small vessels were not able then to contract
sufficiently to retain the blood; it is as in our injections which
ooze from the mucous surfaces, because life no longer opposes their
passage. Observe that when these hemorrhages are produced by an organic
disease, it is almost always that portion of mucous surface nearest the
organ, that is influenced by it. Thus in the last stages of disease of
the heart or the lungs, the patients often spit blood; they pass it by
stool, towards the termination of those of the liver, or even throw it
up by vomiting, &c. The whole mucous system never loses its forces so
as to pour out blood everywhere; it is only in a determinate part that
it is weakened.

What disposes the mucous exhalants more than all the others to pour out
blood? It appears to be because the capillary system whence they arise
is constantly entered by blood, and the course is very short from this
fluid when present in the capillaries to the mucous surfaces. This is
so true, that those portions of the mucous system that have but little
of this fluid in a natural state, as those of the sinuses of the face,
of the ear, &c. are less subject to hemorrhages. I am confident, that
if there were exhalants upon the muscles to pour out constantly a fluid
upon the exterior of these organs, hemorrhages would be very frequent
in them.

Hence we see that the mucous hemorrhages have nothing in common,
but the extravasation of blood, with those which are the effect of
hemorrhoids, and always suppose a rupture of the veins, with those
that aneurisms or varices produce, with those that are the effect of a
cut, of a violent concussion, &c. They form a class by themselves, and
resemble those only that the exhalants furnish upon the other surfaces
where they open.

If I should class hemorrhages, I should distinguish them, 1st, into
those that come from exhalation; 2d, into those that are produced
by rupture. I should place among the first the bloody sweats, the
mucous, serous, cellular hemorrhages, &c.; among the second, those that
accompany wounds, aneurisms, &c. In order to embrace in one view all
the sanguineous evacuations that can happen in the animal economy, I
think it absolutely necessary to adopt this division which moreover
accords with the phenomena and treatment of hemorrhages. Would you
bleed to arrest a hemorrhage from rupture? undoubtedly not; but you
would bleed to check an active hemorrhage by exhalation, because by
diminishing the mass of blood, you diminish the excess of organic
sensibility which produces the hemorrhage; it is nearly the same as
when we bleed for inflammation. It is certainly necessary that the
hemorrhage should be stopped as it has been produced; it is necessary
that the sensibility of the exhalants should return to its natural type
before the blood ceases to flow. We do not bleed to draw the blood
to another place, as has been said; if it was so it should be done
in passive hemorrhages. Most of those who bleed much in hemorrhages,
believe that plethora is the sole cause that produces them, that the
vessels containing too much blood, require a part of it to be taken
away; but there are many more cases of active hemorrhage in which
there are no signs of plethora, than there are of those in which these
signs exist. There may be a real deficiency of this fluid in the
great vessels, but if the exhalants of a part are by their peculiar
sensibility in relation with it, they will pour it out in as great
abundance as if there was an excess of it. It is as in the increase
of natural secretions, exhalations, &c. Whether there was plethora
or not in the great vessels, when the local affection has raised the
peculiar sensibility of the secretories or the exhalants, they would
draw abundantly from the blood. The influence of plethora upon the
increase of the different fluids which are separated from the blood,
is evidently one of the remains of the opinions of Boerhaave. If the
heart agitated everywhere the fluids, if it propelled the blood, the
serum, &c. that go out by the exhalants, the, secreted fluids that go
out by their ducts, this influence would necessarily be real; but since
all the fluids going from the capillary system are necessarily beyond
every action of the heart, as in their circulation, they are wholly
under that of the organic sensibility and tone of the capillaries,
it is evident that these fluids are independent of the quantity of
blood contained in the great vessels and moved by the heart; that the
alterations of the vital forces of the part are the sole causes of the
different phenomena that their course exhibits.

Who does not know that feeble and delicate temperaments are often
subject in women to a much more copious menstruation than those that
are stronger, more vigorous, more sanguineous, as it is called? You
will find many results in authors, upon the quantity of blood evacuated
by the catamenia, and you will observe at the same time that these
results do not resemble each other; why? because each womb has, if you
may so say, its own temperament, which oftentimes does not correspond
with the general temperament, because each is disposed consequently to
a different kind of vitality. There is more or less blood then given
at each menstruation, as it is given for a greater or less time, for
some women have at first only a serous fluid, while others have blood
immediately. I cannot repeat it too much, that every vital phenomenon
is necessarily subjected to many irregularities, which arise from those
to which the vital forces are themselves exposed. On the contrary,
every physical phenomenon is almost immutable, because it is the nature
of physical laws to remain always the same.

Hence we see how hemorrhages of the great arteries, which are under
the immediate influence of the heart, should differ essentially from
those of the capillary system and of the exhalants, whose phenomena
are under the influence of the forces of the part where they happen,
whether they arise from rupture or exhalation. Though in fact these two
classes may be essentially different in their principal phenomena, as I
have already said, yet they approximate, because the modifications of
the vital forces of the part have a necessary influence upon them when
they are in the capillary system. Thus astringents, tonics, styptics
and other medicines which evidently act upon the organic sensibility
and the insensible contractility, frequently stop hemorrhages of the
capillary system. The contact of the air, by modifying these properties
in wounds is even sufficient to produce this effect. On the contrary,
ligatures alone can, in the great vessels, resist the powerful
influence of the heart. All styptics imaginable may be heaped upon an
open artery, and they would not check the effect of this influence.
This then is the essential difference between the hemorrhages of the
capillaries and exhalants, and those of the arteries, that every
medicine which acts upon the organic sensibility and tone, can be
advantageously employed for the first, whereas they have no effect upon
the second. I go now to the sanguineous exhalations which are made by
the recrementitious exhalants.


_Hemorrhages of the Recrementitious Exhalants._

The serous membranes are the frequent seat of hemorrhages. The
examination of dead bodies incontestably proves it. Nothing is more
common than to find in the peritoneum, the pleura, the pericardium, &c.
a serum, reddish if a little blood is effused, very red if more, and
even pure blood is found under certain circumstances.

I have made these observations in two different cases, 1st. After
inflammations whether acute or chronic, especially the last. The serous
sac then contains a greater or less quantity of blood, sometimes alone,
more frequently mixed with serum, and now and then even with whitish
and albuminous flakes. The previous inflammation seems to rank these
hemorrhages among the active. 2d. Often at the end of organic diseases,
in which the exhalations of serum increase almost uniformly in the
serous sacs so as to produce dropsies evidently passive, a greater or
less quantity of blood is mixed with this serum. What anatomist has not
observed these bloody effusions in the pericardium, the pleura, &c.? I
have observed that the tunica vaginalis and arachnoides are infinitely
less subject to them than other similar sacs; I have never seen them in
the last, and twice only in the first. I of course do not speak of the
hemorrhages that are the effects of wounds of the head and in which the
blood is effused between the two folds of the arachnoides.

I have carefully examined the internal surface of the peritoneum, the
pleura, and the pericardium, after this kind of hemorrhages, produced
either in consequence of the inflammation of the membrane itself, or of
an organic disease; their surface has appeared to me to be perfectly
sound, so that it is very evident that the exhalants have furnished
blood, instead of the serum they threw out there before.

I compare a serous surface preternaturally pouring out blood after
inflammation, with the active hemorrhages of the mucous surfaces. On
the other hand, when the serous exhalants throw out blood at the end of
organic diseases of the heart, the womb, the lungs, &c. it is certainly
the same phenomenon, as when blood brought by the mucous exhalants,
under like circumstances, is thrown off by spitting, vomiting, or stool.

Are there cases during life, in which the blood, poured out by
exhalation upon the serous surfaces, is afterwards taken up by
absorption? I believe that it may happen after inflammation, though
we are possessed of no positive facts upon the subject. Cruikshank
and Mascagni have seen the blood absorbed by lymphatic vessels, after
wounds of the chest; why might not that happen after hemorrhages by
exhalation, which takes place after those from rupture?

The cellular exhalants frequently pour out blood in the cells. 1st.
This phenomenon is often very evident in phlegmon or in other similar
tumours. By cutting into them, in the dead body, we find blood
extravasated in the cells; this is so true, that some authors have made
the nature of inflammation consist in this extravasation. But in slight
phlegmonous inflammation, the blood undoubtedly remains in the cellular
capillary system; it is only in those cases where the inflammation
is very great, that this passage takes place. 2d. As to the passive
hemorrhages of the cellular texture, who does not know that oftentimes
the water in dropsies is reddish? who does not know, that in scurvy,
considerable portions of the cellular texture are infiltrated with
blood, which has certainly not been poured out by erosion? I injected
not long since two subjects, with very evident scorbutic spots on the
legs, and there was no kind of extravasation in them; there would have
been if the rupture of the vessels produced these spots. As these
things did not arrest my attention particularly in former years, I did
not pay much attention to many subjects that I have injected with these
scorbutic spots. I do not think that they would ever have presented
cellular effusions, which would undoubtedly have struck me if they were
there, when I dissected bodies for the students.

As to the hemorrhages of the medullary exhalants, we are ignorant of
them. I have never seen in examinations of dead bodies, blood effused
in the articulations, except from wounds, &c.

As to the nutritive exhalants, it is evident that every sanguineous
exhalation is foreign to them.


_Preternatural Exhalations, not Sanguineous._

The blood is not the only fluid that sometimes passes by the exhalants
instead of the fluids that these small vessels naturally pour out. Who
does not know how much the sweat differs? Sometimes water is almost
alone transmitted by the skin; at other times the sweat is filled
with many substances more or less heterogeneous; it is more or less
salt; we know how very different at times is the odour of it. Observe
the many substances that are thrown out upon the external surface by
the exhalants, in the small pox, measles, scarlatina, &c. in herpetic
affections, in different eruptions; compare the critical sweats with
those that are natural, and you will see that the exhalants are, if
I may so express myself, a common passage, which all the substances
contained in the body can pass through, and which in fact they do pass
through in certain cases, when, among the numerous modifications of
which the cutaneous organic sensibility is susceptible, they find those
that are in relation with them. Shall I speak of the serous exhalants?
observe that the surfaces of the same name, according as they are
affected, pour out many different fluids, a milky serum, and a thick
substance that attaches itself to their surface in the form of a
compact membrane, &c. If you have opened but little the bodies of those
who have died of chronic peritonitis, you must have been astonished
at the diversity of fluids then contained in the peritoneum. Grey,
yellowish, fetid, without odour, thick, viscid, thin, &c. &c. these
fluids are hardly twice the same. The serum appears to be always the
general vehicle; but the substances that it contains, by the effect
of the change that disease has produced in the vital forces of the
membrane, are infinitely variable.

Thus we shall see that the glands are a common way, through which pass,
according to the manner in which they are affected, many substances
which differ essentially from those that compose the secreted fluids in
the natural state.


IV. _Of the Preternatural Development of the Exhalants._

The exhalants are developed preternaturally in many parts; it is
especially in the cysts that this development is best seen. Their
internal surface, ordinarily smooth, pours out very different fluids,
according to the particular sensibility they possess. When we open
these cysts, the exhalants furnish new fluids, and it is often
necessary to remove them to prevent exhalation. Sometimes instead of
the fluid that is ordinarily exhaled there, the blood is thrown out, as
happens on the serous surfaces; for example, I have found very bloody
serum in the encysted dropsies of the ovarium; latterly I have seen
in them coagulated blood. I would observe that this is an essential
difference to be added to those mentioned above, between the fluids
that are exhaled and those that are secreted. These last are never
preternaturally poured out in a cyst. We never find preternaturally
a quantity of bile, of urine, saliva, serum, &c. whilst we often
find serum, as in encysted dropsies, fat as in steatoma and other
tumours which have a fatty liquid analogous to this fluid, synovia,
as in the tumours called ganglions, when they are not dilatations of
the synovial glands, which have cysts preternaturally produced, &c.
Whence arises this difference? it would be necessary that the glands
should be preternaturally developed in our parts, in order that the
secreted fluids might be preternaturally separated from the blood, now
the structure of these organs is too complicated, their organization
supposes too many conditions, to admit of their preternatural
development. On the contrary, the simple organization of the exhalant
surfaces, which have only vessels continuous with the arteries, and
without an intermediate organ, requires much less for them to grow
preternaturally in parts, in which they were before unknown.

Sometimes the fluids exhaled preternaturally do not collect in a cyst;
they continually flow out; this is what takes place in fistulas, and
other preternatural or artificial drains that are made in our organs.
Then the cellular texture, constantly preserving the preternatural
modification of sensibility that it has taken locally from a deposit,
or any other circumstance, constantly continues to pour out a fluid
different from the serum that is exhaled in a natural state.



ABSORBENT SYSTEM.


This system results from the union of a multitude of small vessels
which arise from all the parts, and carry different fluids that are
poured into the black blood, after having passed through certain
peculiar swellings that are called lymphatic glands, and which make
a part of the system with them. The whole of the absorbent system
comprehends then two things, 1st, the vessels; 2d, the swellings or
glands, an improper name, inasmuch as it assimilates them with organs
which pour out fluids by the excretories that arise from them.


ARTICLE FIRST.

_Of the Absorbent Vessels._

We shall examine these vessels in their origin, their course and their
termination.


I. _Origin of the Absorbents._

The origin of the absorbents can hardly be demonstrated by inspection;
it is like the termination of the exhalants. Such is in fact the
extreme delicacy of these vessels at their origin, in most parts,
that they cannot be seen with the best optical instruments. In some
places we see pores; but it is difficult to distinguish their nature,
whether they are exhalant or absorbent. Their origin then must be
determined by the phenomena they produce in different places. Wherever
absorption takes place, it is evident that there they begin. Now in
examining attentively the phenomena of absorptions, we see that they
are discoverable whenever there are exhalations; so that the same table
may serve both for the absorbents and the exhalants; the following is
the table for the first.

             ┌1st. exterior, arising ┌1st. mucous.
             │ from the systems      └2d. dermoid.
             │
             │                 ┌1st. serous.
             │                 │2d. cellular, ┌1st. fat.
             │                 │ and taking   │
             │                 │ up there,    └2d. serum.
  ABSORBENTS.│2d. interior,    │
             │ arising from    │              ┌1st. the short and flat
             │ the systems     │              │ bones, and the extremities
             │                 │3d. medullary │ of the long ones.
             │                 │              │2d. the middle of the
             │                 │              └ long bones.
             │                 │
             │                 └4th. synovial.┌1st. the articulations.
             └3d. of nutrition.               └2d. the tendinous grooves.

Let us examine these different absorptions, of which I shall not give
the proofs here in detail, because these proofs will be shown in each
system from which the absorbents arise. 1st. The external absorptions
do not correspond precisely with the exhalations of the same nature.
In fact, neither the sweat nor insensible transpiration exhaled by
the skin, are taken up by the cutaneous absorbents; these fluids
are excrementitious. So the mucous absorbents allow the pulmonary
transpiration to evaporate, and the other fluids exhaled upon their
surface, to mix with the aliments and afterwards to pass off. It is the
substances contained in the atmosphere, in the surrounding bodies, &c.
that this kind of vessels takes up by a very irregular absorption, as
we shall see, except however that of the chyle, which is not made in a
continuous manner, which is subject to great intermissions, and which
at other times takes place with remarkable activity.

2d. The internal absorptions, on the contrary, every where correspond
with the analogous exhalations. Thus the absorbents take up, upon the
serous system, the serum, upon the cellular system the serum and fat,
upon the medullary system the marrow, upon the synovial system, the
synovia; fluids, all of which as we have seen, had been thrown out by
exhalation upon their respective surfaces, and had remained for an
instant upon them. These absorptions are made in a constant and regular
manner; it is in this that they differ from the preceding. The internal
absorbents, incessantly in action, take up in a given time the same
quantity of fluids; their action corresponds precisely with that of the
exhalants. Observe that there are two essential differences between the
external and internal absorptions; viz. that the one are exerted on the
one hand on fluids different from those exhaled upon their surfaces,
and that on the other they are subject to continual variations and
irregularities; whilst the others always take up the fluids exhaled
upon their surfaces, and are constant and regular, at least in a state
of health. I shall point out in the mucous and cutaneous, systems, the
cause of this important difference.

3d. As to the nutritive absorptions, we know much less of them than
the preceding; but nutrition evidently supposes them. There is in fact
in this function a double motion, one of composition, the other of
decomposition. No organ, no part of an organ is formed at one period
of the same elements that composed it at a former one. The ancients
thought, without positive proof, that the body was renewed every seven
years. Whatever may be the period of its renewal, we cannot deny that
it is continually composed and decomposed; now the exhalants perform
the first nutritive motion, the absorbents the second. Observe in
fact, that the internal substances never re-enter the circulation to be
afterwards thrown out, except by the way of the absorbents.

The nutritive absorptions differ then from the preceding, in this, that
the substance deposited by exhalation and taken up by them, remains in
the organs, makes a part of them, and contributes to their composition;
whilst the fluids with which the internal exhalations and absorptions
are concerned, after having been furnished by the one, and before being
taken up by the other, remain out of the organs, upon their surface or
in their cells, but do not make a part of their structure.

It is difficult perhaps to conceive how solid nutritive substances
can be absorbed by vessels so delicate. Hunter, to whom anatomy owes
much both as it respects the absorbents and their uses, has already
removed this objection. It may be added to what he has said, that the
distinction between solids and fluids is not substantial except when
they are in mass; but when they are considered as separate particles,
they do not differ; this is so true, that the same particle makes
alternately part of a solid and a fluid, as in water that is not frozen
and that which is, as in solid or melted lead, &c. Now the nutritive
substances are absorbed particle by particle; then the distinction of
fluid and solid is of no consequence in the function of absorption.

Since the origin of the absorbents is beyond the reach of our senses,
it is difficult, it is impossible even to determine the manner in which
they arise, the peculiar structure which distinguishes them at their
origin, their communications, &c. They undoubtedly differ essentially
according to the mucous, cutaneous, serous, synovial, cellular,
medullary surfaces to which they belong; undoubtedly the nutritive
absorbents differ remarkably from the others; but nothing can be proved
by inspection. What has not been said upon the villous coat of the
intestines considered as the origin of the lacteals, upon their small
bladders, upon the form of the pores of the peritoneum, the pleura,
&c. upon the cellular sponge? I shall not notice here these anatomical
hypotheses, which have been made by an abuse of the microscope, and
which besides, if they had any real foundation, would not lead to any
inference useful to science.

Do the absorbents arise from the capillary system? Judging by
injections, it would seem that they did, for many distinguished
anatomists, by forcing a fine injection through the arteries, have
filled the absorbents in the neighbourhood. I never saw any thing
similar to it myself, yet I am far from denying a fact attested by
Meckel. If many other experiments should confirm it, it would be
established incontestably, it is evident, that the origin of the
absorbents is in the capillary system, as the origin of the excretories
and exhalants are proved to be in the same system. Besides, the
phenomena of absorptions cannot give us any light upon the mode of the
origin of the absorbents.

Where they go off from the surfaces or the organs from which they
arise, the absorbents are extremely delicate; they elude all kinds of
injection. They appear to anastomose with each other, interlace, form a
complicated net-work, which contributes much to the structure of some
parts, especially of the serous membranes. We know however but little
of this interlacing. It is not until they have run a certain course,
that these vessels are cognizable by our senses, and that we can
consequently study them in a general manner.


II. _Course of the Absorbents._

The absorbents, arising from the different parts that we have pointed
out, go in different ways.

1st. In the extremities, they are divided immediately into two very
distinct courses, the one superficial, the other deep-seated. The
former accompanies at first the sub-cutaneous veins, then runs along
in their interstices; so that when injections have succeeded well,
the whole exterior of the limbs appears to be covered with a kind of
lymphatic net-work. The second goes along the muscular interstices,
principally in the course of the arteries and the veins. Both tend
towards the superior parts of the limbs. When the vessels arrive there,
they approximate each other, and are collected into a bundle, in
which they are fewer but larger than below, and which passes through
certain openings that lead them into the trunk; for example, those of
the superior extremities almost all terminate in the axilla, those
of the inferior in the groin and some in the ischiatic notch. Now as
it is a general rule, that every absorbent should pass through one
or more glands, nature has placed at these openings of communication
of the extremities with the trunk, a certain number of these glands.
Yet before arriving at them, some have already passed through similar
glands placed, in a less number, it is true, in the ham and the bend of
the arm. It is in the extremities that the absorbents run the longest
course without passing through glands.

2d. In the trunk, the absorbents take at first two courses, the one
sub-cutaneous, the other deep-seated, which is found upon the internal
surface of the parietes of the cavities, for example, between these
parietes and the peritoneum in the abdomen, between these parietes and
the pleura in the thorax. The first belongs especially to the fleshy
parietes and the abundant cellular texture that is found on them. The
second belongs to these parietes and the serous surface that lines
them. Besides these absorbents, each viscus contained in the preceding
cavities, has deep-seated and superficial ones; the first go into
the interior of the organ, we see the second on the surface. This
distinction is easily made upon the liver, the spleen, &c. The external
absorbents of the parietes of the trunk, run a long course without
meeting with glands. Those that are spread on the internal surface of
these parietes exhibit a similar arrangement. But those of the viscera
hardly come out of them, before they meet these glands, and pass
through a great number at a time, because they are very near each other.

3d. There are many absorbents upon the exterior of the cranium; but
anatomists have not yet found them in its cavity, which agrees perhaps
with the almost total absence of cellular texture in this cavity. There
are many on the face, superficially, in the muscular interstices, and
around the organs that occupy this region. They descend to the neck,
where they find in their course a very great number of glands which
they successively pass through.


_Form of the Absorbents in their course._

The absorbents differ essentially from the veins in this, that for a
great distance they keep of the same size. Whilst in the venous system
the vessels are constantly becoming larger, so that a branch can hardly
go a few inches without doubling its size, those in the absorbent
system remain for a long time the same. When injected these vessels
appear like long white threads running upon the organs.

It follows hence, 1st. that the lymph never circulates like the blood,
in considerable masses, but always in very fine streams; 2d. that the
absorbents are very numerous; for their number compensates for their
size; thus all the surfaces are covered with them, whilst they have
but few veins and those of considerable size; 3d. that the absorbent
system has not really the form of a tree, like the arterial and venous
systems; the manner of division is wholly different. The absorbents
are very commonly straight; when they are tortuous, their curves are
entirely unlike those of the veins or the arteries. In fact in these
last, when the tubes have become as fine as the absorbents, their
curves are brought near each other and are small in proportion to the
size of the vessel. On the contrary the windings of the absorbents are
great; the curves that result from them have often a very considerable
extent; they wind in long folds upon the extremities, when they are not
straight there.

Viewed externally, the absorbents are not always cylindrical.
When filled with injection, they often appear full of knots; this
undoubtedly arises principally from the valves. Many authors have
represented them as a series of successive contractions; this is
however true only to a certain extent.

I have often seen in living animals, in dogs in particular, evident
dilatations, a kind of little bladders in the course of a lymphatic,
containing serum. It is upon the concave surface of the liver and
the gall-bladder, that I have most often observed them. When these
bladders are pricked with a lancet, the fluid flows out and they
disappear immediately. In making experiments with other views, I once
saw two or three of these small dilatations in the neighbourhood of
the gall-bladder. Having suffered the liver to fall back, to examine
the intestines, I was astonished at not being able to find them an
instant after; they disappeared without doubt by the contraction of
the vessel. I would remark upon this subject, that the liver is the
organ upon which these vessels are best seen in living animals; but it
is necessary to examine its concave face the instant the abdomen is
opened; for the contact of the air by contracting them, soon prevents
their being distinguished.

Besides I believe that in no case are the absorbents as much distended
during life by serum, as they are by mercury from injections. When
these have succeeded well, we see upon many parts a net-work of very
evident vessels. On the contrary, most commonly nothing similar is to
be seen in living animals. With whatever promptness we examine most
of the surfaces which the serous membranes cover, surfaces that can
be laid bare without making the blood flow, nothing is seen, except
sometimes small transparent striæ, which soon disappear. Now it is
impossible that if the absorbents were as full during life, as they are
by injections, but what their transparency contrasted with the colour
of the surrounding parts, would render them evident. I have selected
however very large dogs, to try to see their course better. I believe
that injections double at least the diameter of these vessels.


_Of the Capacity of the Absorbents in their course._

The capacity of the absorbents is remarkably variable; it depends
entirely, in the dead body, on the state in which these vessels were
in the last moments. In subjects of the same stature and age, they are
sometimes very apparent, at others hardly visible. They are double,
treble even, in some dropsical patients, what they are in a natural
state. Many authors say that they have seen branches almost equal
to the thoracic duct, and larger than the trunk of the right side.
To be convinced of the extreme variety of the absorbents, without
the assistance of injections, take the lymphatic glands in different
places, then dissect carefully the parts in the neighbourhood; you
will easily find all the absorbents that go to them. Then you will be
able to satisfy yourself of the extreme variety of their size; we can
even in this way trace them far enough without injection. Sometimes
in order to find the end of the thoracic duct, I take a gland in the
neighbourhood of the second lumbar vertebra; thus following the empty
lymphatic tubes that go from it towards the canal, I find it without
difficulty.

When we are not in the habit of finding immediately the absorbents,
this method of searching for them by means of the glands, which are
always very evident, infallibly succeeds; it cannot be used it is true
in the extremities; but in the thorax and especially in the abdomen, it
is very convenient. For example, by taking the inguinal glands we can
trace these vessels to the thoracic duct, by injecting them, or even
without. Some authors have advised making an opening in the gland and
placing a tube in it; this rarely succeeds; it is much better to open
the vessels that go from the gland, at the place where they go off.

The absorbents usually flat in the dead body, because they are empty,
never exhibit in this state a diameter proportional to that which
injections give them; whatever may be the varieties of capacity, the
fluids that we force into them always increase this capacity. It is
this flattening after death, that often makes us in attempting to open
them with a lancet, cut through both their parietes, and thus render it
more difficult to inject them.

The best proof of the extreme variety of the capacity of the
absorbents, is the necessity of choosing particular bodies in order
to inject them, the very great difficulties that often take place in
finding them in some subjects, whilst they are seen immediately in
others, and can be traced in the inferior and superior extremities,
through the cellular texture, without having glands for a guide. It is
not necessary then, after what has been said, to consider the caliber
of the absorbent vessels in a determinate manner. Constantly varying,
according to the state of the lymph they contain, they have no standard
size to which we can refer their increase or diminution. This is the
peculiarity of all the extensible and contractile canals, like those in
the animal economy; it is that which prevents us from making any kind
of calculation of their capacity.

These varieties of the absorbents are not general as in the veins,
all the great trunks of which, for example, are simultaneously
dilated when there is an obstruction in the lungs. Here sometimes one
only, sometimes many branches enlarge; the others remain contracted.
Sometimes the dilatation is general in a part, very often there are
remarkable disproportions of capacity in the same vessel; it is double
in one place what it is in another, though it has not received branches.

Authors have been much puzzled to determine the capacity of the
thoracic duct. I believe it, for it is never found twice the same.
These varieties do not depend on the constitution of the subject, but
only on the functions, and the state in which these functions are
found at death. Whether it be dilated above, contracted in the middle,
exhibiting below a little bladder, called by some the reservoir of
the chyle, &c. are circumstances the greatest number of which vary
incessantly during life, according to the quantity, the nature of
the lymph, and the obstacles to its course in this or that part. We
find a hundred varieties of the thoracic duct and the absorbents in
a hundred different subjects. The same subject has perhaps undergone
these hundred varieties at the different periods of his life. If life
returned and was destroyed many times in the same man, the venous and
absorbent systems would exhibit a number of varieties equal to the
number of times he had died.

We see from these considerations to what are reduced all these minute
examinations of proportion in the capacity of the vessels, which fill
our books of physiology.

If we compare the amount of the veins with those of the absorbents, it
is difficult undoubtedly after what has been said, to form any precise
idea of it; but we can make approximations. Now the absorbents do not
appear hardly inferior to the veins; as to the branches, for example,
the whole of the lymphatics of the lower limbs, placed by the side of
the capacity of the venous trunks, does not appear much inferior to it.
So in all the other parts, the veins being larger, but the absorbents
more numerous, the disproportion is not very great.

From this it seems as if there would be but little difference between
the trunks that terminate the veins and those that are the terminations
of the exhalant system; however this difference is enormous, as we
shall see.


_Anastomoses of the Absorbents, in their course._

In the extremities, on the exterior of the trunk and the head, in
the intermuscular spaces, &c. the anastomoses are very evident. We
see branches of communication going from one absorbent to another;
so that we might often say that these vessels are bifurcated. But
this appearance is most usually deceptive; for each branch of the
bifurcation is almost always as large as the trunk.

Under the serous surfaces, as on the convex face of the liver, the
lungs, the spleen, &c. the anastomoses are infinitely more numerous; it
is a kind of net-work in the plates of authors; for I confess that I
have never injected this portion of the absorbent system.

The anastomoses of the absorbents are made, 1st. from one vessel to
another that is contiguous to it; 2d. from the sub-cutaneous divisions
to the intermuscular in the extremities, and in the organs, from the
sub-serous divisions to those that occupy the interior of these organs.
3d. They take place between the absorbents of the superior regions and
those of the inferior; 4th. between those that go to the thoracic duct
and those that go to the great lymphatic vessel of the right side, &c.

By these anastomoses we understand how a tube with mercury, being
placed in one absorbent, many others around it are filled. They are so
much the more necessary, in the system of which we are treating, as
the lymph is subject, like the black blood, to an infinite variety of
causes of delay in its course, from the want of an agent of impulse at
the origin of the absorbents.

Gravity, external motions, different compressions, &c. have upon the
motion of this fluid, the same influence as upon that of the veins;
gravity especially has much influence. We know that if the powers are
a little diminished after long diseases, too long standing renders the
legs œdematous; hence why they are always more swelled in the evening
than in the morning. As to compression, if it is only moderately great
and acts upon many absorbents, it also produces œdema. It is not
the size of the surface compressed that has an influence upon this
phenomenon; it is only the number of absorbents that pass through this
surface. Thus by the head of the humerus being in the axilla, the arm
is frequently made to swell, whilst more extensive compressions across
the deltoid muscle, where there are fewer absorbents, do not produce
this effect.

From these phenomena, it is necessary then that there should be the
same means to favour the lymphatic circulation, that there are to aid
the venous. These means are especially the anastomoses; it is by them
that the first of these circulations is continued, notwithstanding
all the external obstacles that our clothes in certain places create,
notwithstanding the different pressure that the organs make upon
each other. It is only when the whole of the absorbents of a part is
compressed, that the motion of the lymph is interrupted. Thus the womb
becoming very large in pregnancy, and pressing upon all those of the
lower extremities, these extremities become dropsical. I hardly know
any organ in the abdomen but this, which by its position can produce
these general infiltrations by compression. The liver and all the
other organs are not capable of producing a similar phenomenon. When
dropsy takes place from an affection of them, it is rather because the
functions of the exhalants are increased.


 _Remarks upon the Difference of Dropsies that are produced by the
 increase of exhalation, and those that are the effect of a diminution
 of absorption._

This leads to an observation that appears to me to be very important
in dropsies, viz. the determining when the defect of the action of the
absorbents produces them, and when they arise from the increase of that
of the exhalants.

1st. Whenever a tight ligature applied to a limb makes the lower part
swell, whenever too long standing, a perpendicular position of the
superior extremities, &c. produce the same effect, it is to be presumed
that the effusion depends upon the compression of the lymphatics, and
takes place then like venous dilatations in similar circumstances,
because the lymph finds it difficult to circulate. Here then is a case
in which the exhalants have nothing to do with the dropsy, which takes
place because the absorbents do not take up what the exhalants furnish.
If other causes, as a bruise, a wound, &c. diminish the activity of
the part, the absorbents directly weakened, are not able to take up
their fluids. So if their weakness is sympathetic, that is to say, if
it arises from the injury of another viscus, the same phenomenon will
be the result of it. In all these cases we find the absorbents much
dilated in the dead body: often they are even full of fluids.

2d. But in the organic affections to which dropsy succeeds, the
exhalants certainly in the greatest number of cases, pour out more
fluids than usual. The pleura is filled in phthisis, the skin is
then covered with night sweats, blood is raised, &c. These are the
exhalations which I have called passive. They are so abundant on the
serous surfaces, that if a puncture is made, the peritoneum often fills
again with such rapidity, that as much water is collected in a day,
as there would be in a month, if the exhalation was natural. I do not
say that the absorbents are not also affected in these cases; but the
principal cause of the dropsical effusions is certainly then in the
increased action of the exhalants. I could cite other examples, but
this is sufficient. Four years since I was engaged upon the absorbents;
I observed then that these vessels are not always very evident in
dropsical patients, notwithstanding what has been said by many authors,
and that very often we see them more easily in very thin subjects. I
had not then thought of this difference of dropsies; but in working
again upon this system for my Descriptive Anatomy, I think of comparing
the cases in which it is dilated and those in which it is not, with the
cause of the death.


III. _Termination of the Absorbents._

All the known absorbents unite into two principal trunks. One of
these, which is the thoracic duct, receives all those from the lower
extremities, abdomen, the greater part of the thorax, and those of the
left side of the superior parts. The other is formed by the union of
the absorbents of the right side of the superior parts, as well of the
head, as the extremities, and of some of those of the thorax. These
two principal trunks go into the vena cava superior; around them, many
smaller branches also terminate there.

If we examine but little the number of the absorbents distributed
in all the parts, it will be easily understood, how enormous the
disproportion of their capacity is with that of these two trunks. How
is it that all the serum contained upon the serous surfaces and in the
cellular texture, that all the residuum of nutrition, that all the fat,
the medullary fluid, and synovia, that all the drinks, all the product
of the solid aliments that constantly enter the circulation, can pass,
in order to get there, through vessels so small? This observation has
struck all authors; and it is, I confess, very difficult to explain.
In fact, 1st. When there is a disproportion in the capacity of the
blood vessels, it is compensated for by an increase of velocity where
the caliber is less; thus, though the capacity of the veins exceeds
that of the pulmonary artery, still all the blood of the first passes
through the second. Now if we examine in a dog the thoracic duct during
digestion, which can easily be done by opening quickly the thorax on
the right side, raising the lungs of that side, and by cutting the
pleura along the aorta, which allows you to see immediately this canal
then very white on account of the chyle that is passing through it, if,
I say, we examine the thoracic duct in action, we shall see that the
circulation goes on there nearly as in the veins. By opening it then,
a more powerful throw of fluid does not indicate a greater velocity
than that of the venous blood. 2d. It might perhaps be said that during
life the thoracic duct is sufficiently dilated to correspond to all the
absorbents; but observation proves precisely the contrary. The thoracic
duct, full of chyle, is undoubtedly a little more dilated than in the
dead body; but I have satisfied myself repeatedly that the difference
is not very great. 3d. By supposing that a great quantity of fluids
passes through the thoracic duct, notwithstanding its size, the vena
cava superior ought to be proportionably dilated between it and the
heart; yet it continues nearly of the same size after having received
this canal. 4th. Hewson, by taking the fluid of the lymphatics, has
proved that it was analogous to that of the serous surfaces; its
transparency, when examined in the vessels of a living animal, makes me
also believe it, though this would not be a conclusive reason. How can
a fluid of the same kind, result from the combination of such different
elements, viz. of those which compose the mucous, cutaneous, nutritive,
fatty absorptions, &c.

I confess that the different substances that enter the black blood by
the thoracic duct and the one corresponding to it, may enter it at
different times; that the lymph, the fat, the chyle can each have their
time of passing. But first this explanation is not supported by any
fact, and the disproportion would also then be very great.

Many distinguished anatomists have thought that the veins absorb,
and in relation, to their use, they have joined these vessels to the
lymphatics. Haller, Meckel, and before them, Kaw Boerhaave, were of
this opinion. Such names deserve undoubtedly an examination of the
reasons advanced; let us now consider these reasons. 1st. The thoracic
duct has been seen obliterated, and absorption continuing to go on,
while life was preserved in the animal. But as they have not observed
whether the great right lymphatic and its accessories were obliterated,
nothing can be concluded from this fact. Besides the observations upon
this point do not appear to me to be well ascertained. They could
decide this question very easily, I think, by tying during digestion,
the thoracic duct at its entrance into the jugular; it could be
readily come at on the inferior part of the neck, where it could be
distinguished by its whiteness; no important part need be wounded.
This experiment would throw great light upon the general question of
absorptions. 2d. Fine injections, made through the mesenteric vein,
cover the peritoneum; hence it has been concluded that the absorbents
terminate in this vein. But as the venous extremities communicate
with the capillary system, and as this gives rise to the exhalants,
injections, by going through its numerous anastomoses, can easily be
spread in this way, which vitality shuts during life, but which the
flaccidity of the parts and the absence of sensibility open after
death. 3d. Compression of the superficial veins produces swelling of
the limbs; but as this compression is made at the same time upon the
absorbents, no inference respecting venous absorption can be drawn from
it. 4th. Kaw Boerhaave having introduced water into the intestinal
canal, it was afterwards found in the mesenteric veins; but this
experiment has been many times repeated since without giving the same
result. 5th. Add to these considerations the numerous experiments of
Dr. Hunter, to prove that venous absorption does not take place on the
surface of the intestines, and you will see that this absorption will
appear very uncertain, in these first respects.

But if you look at the question in other respects, you will be unable
to deny that certain facts present probabilities in favour of this
absorption. 1st. It is almost certain, that the venous extremities
take up by the way of absorption, the blood effused in the corpus
cavernosum. 2d. We do not see absorbents in the placenta, and yet the
umbilical vein takes up all the fluids of this body. 3d. Meckel having
injected a lymphatic vessel that went to a gland, the injected mercury
passed into a neighbouring vein.

All these observations throw great obscurity upon the termination of
the absorbents. I think that if on the one hand, we cannot doubt that
the greatest number of these vessels, those especially that come from
the serous surfaces, from the cellular texture, from the intestines,
have known terminations, we ought on the other to suspend our judgment
as to the manner in which the others terminate, and that the question
must remain wholly undecided upon this point, till it has been settled
by new experiments. Here, as in so many other points, physiology
has need of great light. 1st. The enormous disproportion between
the absorbents and their common trunks; 2d, the impossibility of
understanding from the analogy of the veins, the lymphatic circulation,
with the apparatus that injections exhibit as its vessels; 3d, many
probabilities against and many in favour of venous absorption; 4th, no
other known way for the fluids which enter the blood by the absorbents,
than the trunks noticed above. There is nothing but obscurity and
contradiction in the different data which would assist us to resolve
this problem.


IV. _Structure of the Absorbents._

This structure, capable only of being seen in the great trunks,
the thoracic duct, for example, presents us at first in its common
organization, a layer of dense cellular texture, of the same nature
as that of which we have already so often spoken, of which we shall
speak again, and which is found around the arteries, the veins, the
excretories, under the mucous surfaces, &c. &c. This filamentous
texture, connected only to a certain degree with the vessel,
strengthens it however much, by surrounding it with an external
membrane superadded to that which is peculiar to it. If, as Cruikshank
has done, we turn this duct inside out, and introduce into it a tube of
glass of a diameter a little larger than its own, this last membrane
will break. It is as in the arteries, in which a ligature cuts the
internal membrane and not the cellular. The same phenomenon takes place
from inflation; a much greater effort is necessary then to break the
cellular texture, than to rupture the peculiar membrane of the thoracic
duct.

No fleshy fibre is observed, in an evident manner at least, in the
absorbents. Some authors have admitted that they were there, but
injection contradicts them, even as it regards the thoracic duct. Blood
vessels probably run over the parietes of the absorbents; in ordinary
injections they are often very conspicuous on the thoracic duct. We
know not if there are nerves there; there is but little appearance of
them, if we may judge by the analogy of the veins, which have a great
relation in structure with these vessels.

The internal membrane which forms the peculiar texture of the
absorbents is continuous with that of the veins, and forms with it an
uninterrupted series of small tubes. Delicate, transparent, it is
moistened in the dead body by an unctuous fluid, which is, I believe,
unknown to it in the living, as that of the arteries is to those
vessels. It adheres to the external membrane by a compact cellular
texture, which, as in the veins, is rarely subject to ossification.
Mascagni has however mentioned an instance of it in the absorbents of
the pelvis. But there is another affection analogous to this, which
I have already seen many times in this kind of vessels. Their cavity
often contains a white matter, like plaster, especially on the external
surface of the lungs. Then without any preparation, the absorbents
exhibit almost the appearance which they have when mercury fills them.

The peculiar membrane, forms by its folds, valves similar to those of
the veins, but much more numerous. We find these united two by two,
rarely one exists alone. They leave between them small intervals, very
variable however in extent. Hence it happens that the thoracic duct
can sometimes be injected from above below through its whole extent,
sometimes it receives the fluid only in a short space, according as
the valves are more or less numerous in its cavity; which depends also
much on the relation of their width to the caliber of the vessel, a
relation which varies from the same causes as those assigned for the
veins. Hence it happens, that an absorbent filled with injection does
or does not exhibit in great number those knots, which, as we have
said, indicate valves. Wherever a branch is united to a trunk two of
these folds exist at the place of their junction. This is remarkable
especially in the thoracic duct, which injected from above, presents
a dilatation at the origin of each branch, because in this place the
valves are opposed to the fluid. Not numerous in the superficial system
of the organs covered by the serous membranes, as upon the convexity
of the lungs, and the spleen, they easily allow the passage of the
mercury from one division to another, and their ordinary functions are
supplied there by the great number of the anastomoses.

Their use is the same as in the veins, viz. to permit the ascent of
the fluid, and to prevent its return; but they do not always fully
do this. Injection often without difficulty overcomes some of them.
In dropsies, in which the absorbents are full, if we raise the skin,
we easily distinguish these vessels by their transparency; but soon,
notwithstanding their valves, they become empty, and then cease to be
visible. Different anatomists have forced air, and even other fluids,
into a great number of the lymphatics, by means of the thoracic duct,
and consequently in an opposite direction to their valves. All these
phenomena do not suppose in these vessels, as in their common duct,
varieties in the structure of the valves, in their width, &c. but only
different degrees of dilatation and contraction, degrees that are, as
I have said, independent of structure. In dilatation, the valves close
the caliber less than in contraction.

The valves of the absorbents have the same form and the same
arrangement as those of the veins; they partake, by their constant
exemption from ossification, of the general character of the membrane
from which they arise, and which, by folding, forms them.


ARTICLE SECOND.

LYMPHATIC GLANDS.


I. _Situation, Size, Forms, &c._

These glands are scattered in the different parts in greater or less
number. In the superior and inferior extremities, we find but a small
number, except at the upper parts, the axilla and the groin. In the
ham and at the elbow there are some, and there are engravings of them
at the instep. But upon the arm, the leg, the thigh, the fore-arm, &c.
they are not found. It is about the articulations that all are met
with; in this respect, we can say, that they are constantly increasing
from the inferior to the superior, no doubt because in ascending the
number of absorbents is continually increasing.

Not numerous on the cranium, they are only on the exterior of this
cavity, no one has ever, I believe, been found within it; which proves,
perhaps, that it is not the tenuity of the absorbents that conceals
them from us there, but that it is because they are of a peculiar
nature and different from that of the others. The face contains many of
these glands, especially along the stenonian duct, upon the buccinator,
&c.

As to the trunk, if we take the vertebral column for a term of
comparison, we shall see that there are but very few lymphatic glands,
hardly any at its posterior part, and that they are very numerous
anteriorly. On the neck, the jugulars are accompanied by a great series
of these glands. In the thorax, the posterior mediastinum contains many
of them. In the abdomen, they are abundant along the vertebral column,
behind the mesentery.

The whole interior of the thoracic and abdominal cavities, considered
otherwise than as it respects the spine, is also furnished with
them. They are very near each other in the mesentery, at the root of
the lungs, around the bronchiæ and in the pelvis. We see from this
arrangement, that, 1st. the lymphatic glands are found in general more
numerous in the places where the cellular texture predominates, in
which they are, as it were, buried, a remarkable relation for which
we are unable to assign precisely the reason. There are but few parts
abounding with this texture, that do not also abound with lymphatic
glands, and reciprocally there are none of these glands where it is
wanting. 2d. We see also that the parts the most distant from the
common trunks of the absorbents, as the extremities, the head, the
back, &c. are less provided with these glands; that the nearer we
approach these common trunks, the more numerous they become; so that
we might say that they form around them a sort of boundary, which
separates them from the secondary absorbents, and which at the same
time makes them communicate with them.

The size of the lymphatic glands, is variable, from the tenth of a
line in diameter, to the size of a hazle-nut, and even larger. They
are oftentimes so small that we can with difficulty discover them, and
they cannot sometimes be seen until disease has developed them. Their
increase in size is an ordinary effect of scrophulous affections,
which often show us lymphatic glands in places where we did not know
that they existed, especially on certain parts of the face and neck.
We cannot say then that the swellings of the cellular texture deceive
us; for the comparison of these bodies, which are thus made evident by
the disease, and which no doubt pre-existed, with the known lymphatic
glands, and which are then found equally swelled, proves their perfect
identity. All exhibit either the same fatty and white substance, or the
same caseous pus, according to the period of the disease.

In general these glands are much developed in childhood, diminish in
the adult, and almost disappear in old age. They are, it appears to
me, a little more evident in women than in men, in the phlegmatic
temperaments than in the sanguine. Of all the different enlargements of
which they are capable in different places, the tabes mesenterica gives
them the greatest size.

Their form, sometimes oval, sometimes more or less elongated, always
tending to a round one, which is generally that to which all the organs
of animals, and even all those of organized bodies are disposed; whilst
those of inorganic bodies assume those of cubes, prisms, &c.

The lymphatic glands, sometimes insulated as in the extremities of the
limbs, collect in greater number as they approach their common trunks.
The axilla and the groin contain many of them, as I have already said;
but in the abdomen, they are united in a group, and are so close to
each other in the mesentery, that they have appeared to Azelli to form
in this place, not an union of organs, but a single one, which he has
taken for a second pancreas, and to which he has given his name.


II. _Organization._

The colour of these glands, reddish in childhood, grey in the adult,
becomes of a yellowish tinge in old age, and has that subsidence and
flaccidity which then characterize almost all the organs. This colour
varies also according to the regions; thus the bronchial glands have
a black appearance, inherent in part in their structure, but owing
probably also to the fluid that they contain, as the appearance of this
fluid proves, when it is pressed out of a divided gland. This colour
does not depend on its proximity to the lungs and on their colour,
though we know, they have many black spots upon them; the proof of this
is, that I have already very often found the lumbar, mesenteric glands,
&c. also black. Yet there is no part in which this colour would be
more common than around the lungs. Cruikshank, in order to prove the
passage of the lymphatics through the glands, says that he has found
those in the neighbourhood of the liver yellow in jaundice, in which
it is very probable that there is absorption of bile. But this remark
is unimportant, since all the parts of the body, without exception,
exhibit, in this affection, this colour, which is only a little more
evident in the cellular parts.

We cannot deny however but that these glands often take a colour
similar to that of the fluid which fills the absorbents, either in a
natural state, or in injections, on account of the great number of
vascular divisions that penetrate them internally. During digestion, at
the moment the lacteals are transmitting chyle, the mesenteric vessels
become almost as white as this fluid, and soon lose this colour when
the transmission is finished. By filling the absorbent system with
mercury, the same phenomenon is observed.


_Common Parts._

The structure of the lymphatic glands, considered in its common parts,
is as follows; a very abundant, extensible, loose cellular texture
surrounds them, allows them to be moved and easily displaced by the
finger when pushed against them. Hence the remarkable mobility of most
of these organs, in the first periods of their swelling; in which this
texture does not then participate; for it is gradually affected, loses
its laxity, and then adhesion succeeds to mobility. Thus in cancer,
the glands are first rolling, and afterwards become fixed. In acute
inflammations, they are in general fixed, because the neighbouring
texture partakes almost always of the disease.

The cellular texture forms besides around the glands a thick membrane
which more immediately envelops them, and which deprived of fat and
serum, exhibits the nature of the cellular covering of the absorbents.
It is this last membrane which, in the ordinary state, gives to the
glands an appearance in general smooth and polished; for mercurial
injections develop in them some roughness, owing to the prominence
of the vessels that run through them in the interior. Some slight
depressions are also visible on their surface; they are to these
glands, what the furrows on their concave face, are to the liver,
the spleen and the lungs; it is through them that the vessels enter.
We might think that the arteries were very numerous in the lymphatic
glands, if we judged from injections which colour the whole of them,
if they are fine and adroitly used; but little reliance should be
placed upon this. Simple inspection, in a living animal, which is
infinitely more certain, does not discover much blood in these glands.
In the fœtus and in childhood, the quantity of this fluid is much more
considerable; hence in part the redness that characterizes these organs
at this period of life. We are ignorant whether nerves exist in them,
and whether any of the numerous branches that the ganglions send in
their neighbourhood, especially in the mesentery, are introduced into
their texture; I have never traced any of them there.


_Peculiar Texture._

The peculiar substance of the lymphatic glands exhibits a pulp
very analogous to that of the nervous ganglions. No fibre can be
distinguished in them. Soft in the fœtus, withered in the few glands
that remain in old age, this substance, is particularly altered, as
I shall say, by scrophulous diseases, and by the influence of the
affections of the neighbouring organs.

This peculiar texture has a greater or less density. We find it more
solid, and resisting better the injection of mercury in the superficial
glands than in the deep-seated. They have cells at short distances,
especially in childhood; they contain a whitish fluid, which disappears
as well as the cells themselves, at an advanced age. This fluid, of a
very peculiar nature, can only be compared with those of the thyroid
and thymus glands, which, like this, are found as it were extravasated,
in the interstices of the organs that separate them, they have no
reservoirs, and their use is wholly unknown. There is no doubt that the
great quantity of blood that enters the lymphatic glands in childhood,
is owing to the superabundance of this fluid. Sometimes in the adult,
there is a great quantity of it in the bronchial glands, where it
is of a blackish colour. Some physiologists have thought, without
anatomical proof, that it is spread out upon the bronchiæ, and that
it forms in part the black spittle that is thrown out in the morning.
Fourcroy in particular is of this opinion; he attaches importance to
the black colour of these glands, which are perhaps, according to him,
the reservoir of the carbonaceous matter of the blood. The fact is,
they belong to the lymphatic system; that in a great number of subjects
they are grey or red; that we do not know that they have an excretory;
that their texture is pulpy like that of the analogous glands; and that
their size distinguishes them however from all others. I have observed
that the acids, the alkalis and stewing, alter but little their black
colour and that of the fluid contained in them.

It is in the peculiar texture of the lymphatic glands that the
absorbents ramify, after being introduced there in a certain number,
and each with numerous ramifications, and afterwards go out by many
other branches which also give rise to an infinity of smaller ones.
Each gland may in this respect be considered as the centre of two
small opposite capillary systems, which anastomose with each other.
In the interior of these glands, these branches very tortuous, folded
upon themselves in different ways, occupy a great part of the peculiar
texture of these organs which many thought in consequence were nothing
but an interlacing of the absorbents; an idea that is not proved, since
this texture is not yet well known.

I have observed that it is susceptible of less horny hardening than
most of the other animal textures. It approximates in this respect that
of the true glands; but it differs in this, that instead of continuing
to harden by long continued boiling, it soon softens, becomes pulpy,
and breaks with great ease under the finger. The acids after having
crisped it, dissolve it also more easily than many of the other
textures; the sulphuric and muriatic are remarkable for this. Exposed
to the action of the alkalis, it loses some of its principles, which
weaken these menstrua; but it is never entirely dissolved.


ARTICLE THIRD.


PROPERTIES OF THE ABSORBENT SYSTEM.

We shall consider in the same article the properties of the absorbent
vessels and those of their glands.


I. _Properties of Texture._

Extensibility of texture exists in the absorbent system. 1st. The
thoracic duct is distended in an evident manner by injection, before
the rupture of its peculiar membrane takes place. 2d. I have said that
the absorbents examined around the serous membranes in a living animal,
principally in the liver, often exhibit little bladders or considerable
dilatations. Are these dilatations varices? is there an analogous
character in this respect, between the absorbents and the veins? I
know not; whatever they are, they can be very considerable in a long
absorbent vessel. 3d. When we tie the thoracic duct, not only that
swells, but the lymphatic vessels of the abdomen also dilate, and this
ligature is the most convenient means of observing the lacteals. This
extension has undoubtedly limits; carried too far, it would probably
produce in a natural state the rupture of the vessels, as happens
from injections. We have not yet any data founded upon observation
or experiment, respecting this rupture, though some authors have
endeavoured to explain by it the formation of most dropsies.

Contractility of texture is evident in the absorbent system. 1st. When
the thoracic duct is distended even in a recent dead body, and the
fluid is discharged by puncture, it immediately contracts. 2d. All the
absorbents contract also as soon as there is no more fluid in their
cavity. This phenomenon is remarkable during the absorption of chyle;
when that is finished, these vessels evidently disappear by the effect
of this contraction. 3d. The absorbent glands, swelled at the moment
chyle is passing through them, afterwards lose much of their size by
this contractile power.


II. _Vital Properties._

We have but few data concerning the animal properties of the
absorbents. Sensibility of relation does not appear to exist in them;
it is difficult to ascertain this by experiments. When we puncture
a lacteal when it is full of chyle, a lymphatic filled with serum
on the surface of the liver, or even the thoracic duct, the animal
gives no indication of pain. But what inference can be drawn under
circumstances, in which the abdomen being opened, the numerous painful
sensations would render nothing, comparatively, the slight sensation
which the puncture produced, admitting that it existed? No experiment,
I believe, has yet been attempted to ascertain if irritation carried to
the interior of these vessels produces a sensible effect. Probably the
same result would be obtained by fine injections used for this purpose,
as has been for the veins, considering the analogy of structure and the
continuity of the peculiar membrane of both systems.

There are circumstances however in which the absorbents have a very
acute sensibility, viz. when they are inflamed. It is a very frequent
phenomenon in diseases, that there is a very evident swelling and
redness, along the course of the sub-cutaneous absorbents in the lower
extremities, giving considerable pain to the patient, terminating
at the inguinal glands, or even extending beyond. In wounds with a
poisoned instrument, in the acute pains of a whitlow, &c. a very
painful sensation is often felt the whole length of the absorbents of
the superior extremities.

The lymphatic glands do not appear to enjoy, in a natural state, animal
sensibility, when they are irritated in different ways, which can
easily be done. But inflammation may develop it in these glands as in
the absorbents, by raising to a high degree their organic sensibility.
Thus the pain is very acute, when after a puncture made by an infected
instrument, after a sprain, &c. these glands swell. We know the extreme
suffering that arises from those in the axilla, when they swell and
suppuration succeeds. Shall I speak of the pains experienced from the
mesenteric glands when cancerous? Who is ignorant of those which buboes
occasion, &c.?

As to animal contractility, it is entirely wanting in the absorbents
and their glands.

The organic properties exhibit in the absorbent system, the following
arrangement. Sensible contractility has been allowed them by Haller.
It is founded upon this, that the lymphatics easily empty themselves
of the chyle that passes through them, and upon this also, that
by touching them with sulphuric acid, they crisp immediately. But
sulphuric acid, like all the concentrated acids and caloric, produces
the same effect upon all animal substances, even after death; it is the
horny hardening. When the absorbents, particularly the thoracic duct
are touched with the point of a scalpel, no contraction follows. If
they are capable of contracting upon themselves, it appears that it is
when they cease to be distended, and not when they are irritated; and
that it is consequently by their contractility of texture. The sensible
organic contractility is then at least doubtful in them, if it exists
it is very obscure and at most to be compared to that of the dartos
muscle.

The organic sensibility and the insensible organic contractility are
evidently found in the absorbents. It is by these properties that
they perform their functions, that fluids are absorbed by them, that
they circulate in their branches, &c. &c. These two properties are
remarkable in them in this, that they continue some time after death.
A fluid injected when the animal is still warm, is absorbed, either
on the serous or mucous surfaces. It is less easy in the cellular
texture. We can prolong a little this absorbent power, by supporting
the heat artificially by a bath. This has in general less efficacy than
I thought for a long time. Various recent experiments have convinced
me of this. This arises no doubt from the fact, that it is the vital
heat and not an artificial one, which is necessary to the exercise of
this function, or rather vital heat and absorption are two effects of
a common cause, viz. organic properties. As long as these properties
remain in the solids, they retain caloric and absorb. But the moment
they are gone, the heat goes and at the same time absorption ceases. It
would be useless to expose to caloric, solids that life had entirely
abandoned; they would become warm; but they could exhibit no vital
phenomenon. In the same way it would be useless to keep up the heat
of an animal recently killed, by making an artificial one succeed the
natural. It is organic sensibility and insensible contractility, that
must be prevented from escaping to prolong absorption. If artificial
heat keeps up this function, it is only by first keeping up these
properties. We cannot calculate upon absorption when the animal is
cold, though Mascagni and many others have said otherwise. I have in
vain attempted to keep it in action then; generally I have not observed
it above two hours after death. The organic sensibility is in relation
with many fluids in the absorbent system, and it is in this that it
differs from the other systems, the glandular, for example, which is
never in relation but with one particular fluid, and which rejects all
the others in a natural state. Water and other mild fluids can easily
be absorbed, though very different from the lymph. In the natural
state, the thoracic duct alternately admits chyle and lymph.


_Character of the Vital Properties._

From what has been said, it is evident that the organic properties
perform the principal part in the peculiar life of the absorbent
system. These properties are much more conspicuous there than in the
venous system; at least they are much more capable of being raised.
In fact there are ten inflammations of the absorbents for one of the
veins. This disposition to inflame from the least virus that passes
through their tubes, from pains, though not severe, that are felt at
their extremity, particularly characterizes these vessels. It is rare
that there is found in the course of a vein, those swellings, pains
and inflammations so frequent in the course of the absorbents. This
difference proves a diversity of structure in the peculiar membrane,
notwithstanding its continuity with that of the veins. In fact at the
period when experiments were made upon the transfusion of medicines
into them, authors have not related any case of venous inflammation
from the contact of foreign substances upon the membrane of the veins;
whilst practice frequently presents us this fact in the absorbents.

The lymphatic glands especially have a great tendency to inflammatory
swellings, when deleterious substances that are absorbed come in
contact with them. In the first periods these substances confine their
effects to the first glands they meet; thus the absorption of the
venereal virus hardly extends beyond the glands of the groin; thus
the axillaries alone swell when a puncture is made with an infected
instrument, &c.; the glands that follow, remain untouched.

Though much disposed to inflame, the lymphatic glands exhibit however
more slowness in this affection, than many other animal textures,
the cellular and cutaneous, for example. We know that phlegmon and
erysipelas go through their periods quicker, than the inflammations
of the inguinal, axillary glands, &c. The pain of which these
inflamed glands are the seat differs also much from that of these two
affections; it is more dull, obscure, &c. The pus is more slow in
forming; it resembles considerably cellular pus; it differs much from
that of erysipelas. There are few textures in the economy that are more
disposed than this to hardening after inflammation. For one single time
that the skin become scirrhous after erysipelas, the lymphatic glands
become so twenty. This is truly one of their distinctive characters.

The absorbents often exhibit to a certain degree, like their glands,
a character of slowness in the phenomena over which their organic
properties preside. For example, when concerned in a wound, they
contract, crisp up and close more slowly than the sanguineous
capillaries, that are then also concerned; hence the flow of serum
that continues for some minutes after that of blood has ceased.
This phenomenon is constant in small wounds. If the absorbents and
the capillaries had the same degree of insensible contractility, it
certainly would not take place.

Here then are new proofs of the principles of which we have every
instant occasion to present the consequences in this work; viz. that
the vitality peculiar to each system, the particular degree of vital
forces that characterize them, imprint upon all its affections a
peculiar tinge and aspect, if I may so express myself, unknown to all
the other systems.


_Differences of the Vital Properties in the Absorbent Vessels and their
Glands._

Though we have considered at the same time the vital properties in the
glands and in the absorbents, though anatomy shows the first to be an
assemblage of folds and vascular windings, yet it cannot be denied that
they have a peculiar kind of vitality, by which they are distinguished
from the absorbents that come to them. It is this peculiar kind that
exposes them to certain diseases of which the absorbents are not the
seat, at least not in so evident a manner. The scrophulous virus seems
more especially to attack them. They are particularly affected in
tabes mesenterica, strumous diseases, &c. In the innumerable swellings
of which they are the seat in consequence of organic diseases, the
absorbents do not appear at the same time altered in their texture. It
seems even that in a very great number of cases, the numerous folds
that these vessels form in the glands, do not partake of their organic
injury; they, in fact, transmit the lymph as usual. Nothing is more
common than to see abdominal and thoracic enlargements of these glands
in children, without producing serous effusions, even at the most
advanced periods. In opening the bodies of small subjects, I have often
been astonished at this phenomenon. The lymphatic vessels are not even
more dilated, at least we do not find them easier in children affected
with tabes mesenterica, than in others. We can hardly ever discover
them at this age to inject.


_Sympathies._

The absorbent system is much disposed to receive the sympathetic
influence of the other organs. This disposition relates, 1st, to the
glands; 2d, to the vessels themselves.

One of the phenomena which the examination of dead bodies perhaps
most often exhibits, is the swelling of the lymphatic glands from
the organic affections of the principal viscera. We observe this
phenomenon, 1st, in the neck from the affections of the thyroid gland
and sometimes of the larynx, in the jugular glands; 2d, on the
chest from cancer in the breast, in the axillary and often in the
mammary glands, from every kind of phthisis in those that surround
the bronchiæ, very rarely if ever from diseases of the heart, whether
aneurism, ossification or diseases of the valves; 3d, in the abdomen,
from cancerous diseases of the stomach, especially of the pylorus,
and most of those in which the texture of the liver is altered, in
the numerous glands that accompany the biliary vessels and those
surrounding the pancreas; from schirrus of the intestines, from their
cancers, which are in general rather rare, in the mesenteric glands;
from the affections of the womb, the rectum, and the bladder, in
the glands of the pelvis; from schirrus of the testicles, diseases
of the urethra, in the inguinal and lumbar glands, &c.; 4th, on the
superior extremities from punctures, bites and most of the inflammatory
affections in the axillary glands; 5th, on the inferior extremities
from many affections in the inguinal glands.

These swellings of the lymphatic glands are of the same nature as the
affection that produces them; if that is acute they are so, if chronic
they pursue the same course. The swelling of the glands in the axilla
is acute, if it is the consequence of a prick of the finger, of a
whitlow, &c. and chronic, if it arises from cancer.

I am far from considering all these different swellings as the result
of a sympathetic influence exerted upon the gland. No doubt the
conveyance of absorbed matter produces the effect, as happens when
there is some virus, punctures with poisoned instruments, &c. producing
the swelling. But sometimes also sympathy alone is the cause. When by
the acute pain that a whitlow, a splinter under the nail or a bruise of
the finger occasion, the axillary glands swell; when the same glands
swell from the effect of a blister applied to the arm or fore-arm, &c.;
when this phenomenon happens in the inguinal glands from a blister
on the thigh or the leg, of which I have seen many cases, &c. &c.
there is certainly no matter conveyed to the gland; it is an effect of
sympathy.

Most surgeons believe that every cancer in the breast, with swelled
glands, requires their extirpation. I believe that in some cases they
may become cancerous, but I doubt if this happens in the greatest
number. 1st. In old ulcerated cancers of the breast, they continue most
often swelled during the whole of life, without suppurating. 2d. After
operations, in which some deep seated ones have been left, we rarely
see them become cancerous. When the cancer is reproduced, it is the
wound that opens again. 3d. I have many times compared the texture of
a gland of the axilla enlarged by a cancer of the breast, with that of
the bronchial glands enlarged in phthisis, with that of the sub-hepatic
glands swollen from steatomatous tumours, hydatids of the liver, &c.
and I could discover no difference. 4th. Finally, all those who open
many dead bodies may be convinced that almost all the organic diseases
of the viscera which have many glands around them, are accompanied with
their enlargement, whatever may be the nature of those diseases. This
phenomenon struck me so much, that at one time attributed the effusions
which terminate almost all these organic diseases, to the difficulty
the lymph experiences in passing through these glands. But the
absence of these swellings in the diseases of the heart attended with
dropsy, the frequent absence of swelling of the superior extremities
when the axillary glands were enlarged, the tumefaction of the lower
parts, the glands of the superior being alone swelled, and many other
similar proofs, which made me consider the serous effusions that take
place then, as passive exhalations, analogous to those that produce
hemorrhages, did not permit me to adopt this first opinion.

It is essential to distinguish the swellings of the lymphatic glands by
the influence of the diseases of the neighbouring viscera, from those
which arise from tabes mesenterica and other analogous, scrophulous
diseases. 1st. In the latter case, the texture of the gland is always
primarily affected; it is only secondarily in the other. 2d. The one
from scrophulous affections appears exclusively in childhood; the other
at all ages. 3d. Finally, a gland swollen from the affection of another
organ, most frequently preserves a texture, and colour analogous to its
natural state. It is only in the last periods that the texture becomes
sometimes hard, like cartilage, and even suppurates; but it is not
with the same phenomena as the texture of the mesenteric and bronchial
glands swollen by scrophula. The appearance and structure are wholly
different. This last exhibits in this case a white substance which is
found in small quantity in the first periods; so that when we cut the
gland, we easily distinguish this substance from the texture of the
gland that remains, where it still exists, with its natural colour and
arrangement. In the latter periods, this white matter has encroached
upon the whole gland, the texture of which has disappeared. However in
phthisis, and sometimes, though more rarely, in cancers, the swelled
glands exhibit in consequence an analogous appearance; but in all the
other cases it is different.

We know that nature often chooses these glands in important fevers, as
the place of the crisis. They are the seat of what are very improperly
called parotid tumours, in adynamic fevers.

The absorbents are, like their glands, influenced by the affections
of the neighbouring organs. I am well persuaded that the different
alterations which the absorption of chyle undergoes, the absorption
of the aqueous part of the bile and the urine, and the derangement
of those of the serous surfaces in many diseases, are effects purely
sympathetic. But it is not very easy to distinguish when they are
not so. There are certainly sympathetic absorptions, as there are
sympathetic exhalations and secretions.

On the other hand, the absorbent system being affected, the other
organs very often experience sympathetic influences. In tabes
mesenterica, and in the enlargement of the bronchial glands that
correspond with it, there are many symptoms that evidently arise from
the sympathetic relations that connect these glands to the other
organs. It is not my province to point out these symptoms.

As to the influence of the diseases of the absorbents upon the other
organs, we know but little of it. When their course is inflamed from a
puncture, from a wound with an instrument having on it some virus, &c.
there are often vomitings, diarrhœa, &c.


ARTICLE FOURTH.

OF ABSORPTION.


I. _Influence of the Vital Forces upon this Function._

The functions of the absorbents are not at the present day a subject
of doubt with any anatomist; but the manner in which these functions
are performed, are far from being so well agreed upon. The first
idea has been to compare the action of the absorbents with that of
capillary tubes. But if we reflect a little upon this action, it is
easy to see that these phenomena are wholly different from those of
inert, capillary tubes. I think that we never should be able to say
precisely, how an absorbent orifice, being immersed in a fluid, takes
it up, seizes its particles and makes them ascend in its tube. But what
is undoubted in absorption is that the vessels derive this faculty
from the vital forces which they have; that it is only the relation
existing between the particular kind of organic sensibility with which
they are endowed, and the fluids with which they are in contact, that
is the immediate cause of the phenomenon. Do you wish numerous proofs
of this? See the lacteals choosing only chyle from among the variety
of matter contained in the intestinal canal; see the absorbents of the
bladder and the gall-bladder leaving many of the elements of the urine
and the bile, to take only the aqueous part of these fluids; see the
cutaneous absorbents, the mucous ones of the bronchiæ, &c. selecting
only certain principles from the air and leaving others. Often inactive
for a long time, they immediately recommence action when any substances
in relation with their sensibility are presented to them. Observe the
fluids injected or effused into the cellular texture, they are taken
up or left by the absorbents of this texture, disappear promptly, or
remain and occasion suppuration, according as they agree with or are
repugnant to their sensibility.

We cannot deny that in the natural state the sensibility of the
absorbents has a particular type, to which certain substances are
alone accommodated, and which alone on this account can be absorbed.
The exercise of the organic sensibility then always pre-exists in
absorption, as it does in secretion, nutrition, &c. Thus in the
physical phenomena, the exercise of gravity always precedes the fall of
heavy bodies. Thus the power of attracting is put into exercise before
the motion of the planets takes place, &c. &c.


II. _Varieties of Absorption._

It follows from what I have said, that whenever the organic sensibility
of the absorbents is altered in any way, absorption must necessarily
experience a corresponding derangement; now this is what constantly
happens. Serum often bathes for whole months the absorbent orifices,
in dropsy, without raising their sensibility sufficiently to be taken
up by them. Let any cause increase this property, instantly absorption
takes place. Observe some indolent tumours which remain for a long
time in the same state by the stagnation of their fluids, they are
immediately discussed when certain medicines applied to them rouse the
dormant sensibility of their absorbents. Discutients do not act upon
the fluids themselves; they do not attenuate, or cut them, according
to the vague language of physicians, but by changing the degree of
force of the absorbents, they render them able to act. It is so true
that it is in this way that different resolutions are effected, that
often a slight degree of inflammation is previously necessary to their
development; all surgeons know this. Desault did not consider most of
the swellings of the testicles as an obstacle to the operation for
hydrocele by injection. On the contrary it often happened, that after
the irritation produced in the testicles by the surrounding membrane,
the enlargement disappeared, which was only kept up by the want of
energy in the absorbents.

The alterations of organic sensibility can diminish, increase, or
variously modify this property. Let us cease to wonder then at the
extreme variety of the absorptions; let us not be astonished, if many
fluids, besides those ordinarily taken up, can pass into the blood
by the absorbents; if the bile, the urine, the mucous fluids, which
are usually rejected, can enter the circulation; if the blood effused
in the cellular texture is taken up by these vessels. The forces of
life impress, by their extreme variety, the same character on all the
functions over which they preside.

Much has been said of putrid matters passing into the blood, and there
serving as a cause for diseases. This infection of the blood has
undoubtedly been exaggerated; but I am convinced that in many cases it
is real. Why are the colour, consistence, odour, and nature of the
excrements so very variable? If the same substances are always absorbed
from the aliments, it is evident that the residue of these aliments
would always be the same. Observe the innumerable varieties of the
urine, the bile, the mucous fluids, &c. according to the difference
of the principles that concur to form them. Why should not the chyle
present the same variations? it would be the only fluid of its kind
in the animal economy if it did not change under many circumstances.
Now, whence can these changes come, if not from this, that the lacteals
present numberless varieties in their organic sensibility, varieties,
each of which admits only certain principles and rejects the others?

The absorption of the lacteals, which, in an ordinary state, introduces
into the blood only nutritive substances, can then often be a way open
for the admission of many morbific principles. Thus in the lungs, the
vessels which take from the air the substances proper to colour the
blood, often draw in principles injurious to their functions, according
to the different alterations that their sensibility can experience.

In the ordinary state, the kind of organic sensibility and of tone of
the cutaneous and mucous absorbents, shuts out all external substances
that are hurtful. But when this kind is changed, the way can in an
instant be open to them. Does not pus remain without mischief on the
cellular texture, in most wounds? Let an imprudent application raise
there a little the forces of the absorbents, it is taken up by them;
the ulcer dries up; the pus passes into the blood; and then follows the
whole sad train of the symptoms of re-absorption which commences.

We can say, that a thousand channels are incessantly open in our
organs, to morbific principles. The organic sensibility, placed as a
sentinel at their mouths, indicates according to the manner in which
it is affected, to the insensible contractility when it is necessary to
open or shut them.

It is exhalation that contributes to the formation of most tumours; it
is absorption that serves for their cure.

If I were to run over the phenomena of absorption in the different
ages, sexes, seasons and climates, I could show constantly the
differences of organic sensibility always preceding the differences of
this function. I shall speak of them in the different ages.

The causes that vary the natural type of the sensibility of the
absorbents, are, as in all the other functions, direct or sympathetic;
1st, direct, as when by previous friction on the skin, we excite the
absorbents, and force them to act, which they would not have done
without this; 2d, sympathetic, as when the absorbents, feeling the
affection of a distant viscus, increase or diminish their action,
according to the kind of influence they receive. We have spoken of this
phenomenon in the sympathies of the different systems.


III. _Motion of the Fluids in the Absorbents._

The fluids once absorbed on the different surfaces of which we have
spoken, are carried by a successive motion to the common trunks, which
transmit them to the black blood.

We know not the laws of this motion. It is evident from many
observations formerly made, that it has much analogy with the motion
of the venous blood; but it is also distinguished from it by some
differences.

It appears to be in general more slow. The thoracic duct opened when it
is full of chyle, does not throw out its fluid as far as a vein of the
same size.

The motion of the lymph does not seem to be subject to a reflux in the
neighbourhood of the heart, like the venous blood. For example, the
venæ cavæ, jugulars, &c. are so much the more dilated, in proportion
to the obstacles the lungs have opposed to the return of the blood.
Now in injecting the thoracic duct, I have never observed between its
dilatation and contraction, and the state of the pulmonary organ, any
kind of relation. On the other hand, we never find this duct full
of lymph, as we find the veins full of blood, when an obstacle has
interrupted the motions of the fluid in the last moments.

How happens it, that in the reflux that produces the venous pulse of
the jugulars, the blood does not enter into either absorbent trunk? The
valves, arranged to prevent the entrance of that, which in a natural
state, flows towards the heart, are evidently useless here. We can
clearly attribute this phenomenon only to the relation existing between
the orifice of these trunks and the black blood, as the orifice of the
larynx, foreign by its vitality to external bodies, repulses every
fluid but the air. Blood is never found in the thoracic duct.

There is in the venous blood an evident continuity of motion, from the
capillary system to the heart; it is from this system that it goes,
to be propagated, if we may so say, to that organ. The motion of the
lymph, on the contrary, is incessantly interrupted by glands, each
of which, as I have said, exhibits really in relation to the vessels
that enter and go out of it, a small capillary system. At each gland
the motion necessarily changes its impulse; now as the state of these
glands is susceptible of many varieties, we can easily conceive,
that the motion of the fluids circulating in the absorbent system,
necessarily presents a great number of them; that it may be rapid
in one part, very slow in another, regular here, there irregular,
&c. Hence we must not be surprised if we find some absorbent vessels
dilated, whilst those of the neighbourhood are hardly perceptible.
There is indeed a kind of variety in the veins, but it always has its
source in the origin of these vessels, and never in their course, as
takes place in the absorbents.

The continuity of the venous blood and the frequent interruptions of
the lymph should establish differences not only between the motions of
the two kinds of vessels, but also in the composition of the fluids.
The first is necessarily everywhere the same; the second may vary at
every gland, and take new modifications at each of those through which
it passes.

I should be disposed to think that the insensible contraction of which
the small capillary system of each gland is capable, would aid the
motion of the lymph, by diminishing the course that this fluid must
take, without a new impulse, from the origin of the absorbents to the
black blood, if these organs were wanting. In fact, we know that in the
extremities where there are much fewer glands, there are more frequent
effusions than in the trunk where the absorbents pass through them at
every instant; I speak of those effusions which ought evidently to be
attributed to the want of circulation of the lymph, as those arising
from compression, too long standing, &c. and not those that depend on
an increased exhalation, like those after organic affections.

We see, from what I have said thus far, that we have only a few
disconnected views upon the motion of the lymph; that of the veins,
though still requiring much research, is yet more known; but in order
to give a perfect knowledge of these subjects, the first especially,
many experiments and much further labour are necessary.


IV. _Of Absorption in the different Ages._

In the fœtus and in childhood, absorption relative to nutrition is not
in proportion to exhalation. Many substances remain in the organs, but
few go out, hence there is growth.

But little is known of the differences which the internal absorptions
of synovia, serum, fat, marrow, &c. then present.

The external absorptions appear to be more active, for we know that
contagions are taken with much more facility in the first age. We
know not however whether the skin and mucous surfaces then constantly
introduce more foreign substances into the body, or if they are only
more disposed to introduce them.

We are deficient in positive data as to the state in which absorption
is found in childhood. To judge of it however by that of the lymphatic
glands, it would appear that it was very energetic. In fact these
glands are in proportion much developed; they appear to be the seat of
very active functions; they have a peculiar life more developed than
afterwards, hence a greater disposition to diseases. We know that until
puberty, or rather until the end of growth, they are the seat of many
affections which entirely disappear after that age, and lessen the
numerous series of those to which we are exposed.

This double circumstance, 1st, the precocious and proportionably great
development of the lymphatic glands in childhood; 2d, their very great
disposition to diseases, indicates certainly remarkable activity in
their functions; for it supposes a great development of the vital
forces; now these vital forces being more developed ought necessarily
to preside over more energetic functions. See in fact the organs
whose functions we know, which are on the one hand much developed in
childhood, and on the other much disposed to diseases; the functions
of these organs are more active. Thus the brain and nerves being more
developed, have more sensibility; thus the vessels with red blood have
an activity of nutrition, in proportion to their size, &c. In youth,
it is when the genital organs are more developed and they become more
exposed to diseases, that their functions are greater. Examine all
the organs and their functions, you will see that a general law of
the economy is, that these three things, 1st, great development; 2d,
greater disposition to diseases; 3d, greater activity of functions, are
constantly united. Now when these two first exist in the glands of the
absorbents, we ought to conclude that the third is there also, though
we are not certain of it, since, from what I have said, we are ignorant
of the uses of these small organs. Grimaud has considered them, it is
true, as essential to nutrition; he even calls the nutritive system
the combination of these glands and the cellular texture, a gratuitous
supposition, which is not proved. All that we know upon this point, is
that on the one hand nutrition, and the development of these glands on
the other, are very great in the fœtus. But does it follow from this,
that the first phenomenon proceeds from the second? Undoubtedly not;
no more than because the brain, the liver, &c. are early developed in
the fœtus, and nutrition is very active, they should be considered as
the agents of this function. Besides, nutrition is a function that has
no particular organ for its centre and agent. Each organ is itself
the machine which separates from the blood or the fluids that enter
it, the nutritive materials that are suitable for it, and afterwards
appropriate them to itself. The muscle separates its fibrin, the bone
its phosphate of lime, &c. But one common and central organ does not
elaborate these nutritive materials, as one common viscus moves the
blood, as one central organ presides over sensibility, &c.

As to the anatomical state of the absorbents in the fœtus and
childhood, we can know but little; I do not know that any author has
injected them comparatively in this age and in the adult. I have but
one fact upon this point, it is that the lacteals, examined in an
experiment upon two young dogs, who had only left off sucking eight
days, appeared to me larger in proportion than at a more advanced age.
I will make one remark that has often struck me; it is that the size
of the animal has much less influence than would be thought upon the
diameter of these vessels. For example, an adult dog, twice as large
as another, has not by a great deal, vessels of double size. Accident
led me to examine them the same day, three years since, upon two large
grey-hounds, that were among the dogs brought to me, and upon one of
those vulgarly called cur dogs; they were nearly equal in all three;
this struck me.

We know but little of the different revolutions that absorption
undergoes in the ages that succeed infancy. Only there is no doubt that
puberty is the limit of this kind of predominance which the lymphatic
glands enjoyed in the economy. The age of their diseases is then
passed; often even these diseases, heretofore beyond the reach of art,
are spontaneously cured. The predominance of the genital organs which
succeeds to this and some others, those of the sensitive-organs, &c.
seems to destroy the germ which this first supported.

Soemmering has described in a particular work the part that the
absorbents perform in the different diseases of the adult and the other
ages. This part has appeared to me to be often very difficult to be
known, notwithstanding what he has said of it. I refer however to his
work on this point.

In old age, nutritive absorption continues very active; for it is that
which decomposes the body, which takes from it the substances that
nourish it, and which consequently withers and dries the organs.

The external absorptions, on the contrary, are feeble; the skin takes
with great difficulty the different contagions, as I shall say in
treating of this organ; the mucous surfaces absorb slowly; but little
chyle passes into the blood in proportion to what enters it in the
adult. The two absorptions, the nutritive and the external, are exactly
reversed at the two extreme ages of life; the second is superior to
the first in infancy, the first predominates in old age.

As to the internal absorptions, as those of synovia, of the serous
surfaces, of the cellular texture, &c. I should think that they
predominated in old age, and that to this was to be attributed the
numerous serous effusions which happen at that age, and which we
observe in dead bodies. We have not however upon this point so good
data as upon the other two.


V. _Preternatural Absorption._

We can understand two things by this expression; 1st, the absorption of
fluids different from those naturally taken by the absorbents, as that
of effused blood, &c. I have already spoken of this absorption; 2d,
that which takes place in the cysts which are developed contrary to the
natural order in the economy. Now this last exhibits a very singular
phenomenon, when compared with preternatural exhalation. It, in fact,
takes place with difficulty; it is rare that you see the fluids
of encysted tumours enter suddenly the circulation by absorption,
either in whole or in part, as this very often happens in the serous
collections of the peritoneum, which, without being cured, have many
alterations of increase and diminution. What physician has not observed
that the urine flows more as the abdomen becomes flat, and that it is
suppressed when it is filled?

Observe on the contrary, that exhalation is renewed with great facility
in encysted tumours; that if we empty them and do not remove their
cysts, they are soon reproduced, as I have said. Is it that the
absorbents are not developed in proportion to the exhalants in these
tumours? I know not; but the fact is not less certain; observation of
diseases proves it every day.



SYSTEMS PECULIAR TO CERTAIN APPARATUS.


GENERAL OBSERVATIONS.

The former part of this work has been devoted to researches upon
the systems common to the structure of all the apparatus, upon
the primitive systems, which form if we may so say the nutritive
parenchyma, the basis of all the organs, since there is hardly any one
of these organs in which the arteries, the veins, the exhalants, the
absorbents, the nerves and the cellular texture do not enter as a more
or less essential part. Each is at first a texture of these common
parts, then of other peculiar parts which particularly characterize
them.

The systems that will now be examined are not so generally extensive in
the animal economy. They belong only to some particular apparatus; thus
the osseous, the animal muscular, cartilaginous, and fibrous systems
are especially destined to the apparatus of locomotion; thus the
serous, mucous, and organic muscular systems enter especially into the
digestive, respiratory and circulatory apparatus; thus the glandular
system forms the apparatus of secretions, thus the cutaneous system
enters principally into the external, sensitive apparatus, &c.

All the systems that remain to be examined are then much more
insulated, perform a much less extensive part than those of which we
have been treating. Confined to certain apparatus, they are unknown
to the others, and have an independent life of their own, whereas the
primitive systems everywhere mingle their vitality with that of the
other organs, into whose composition they enter; most of them have
a kind of existence and external forms which distinguish them from
these last. The different parts which compose each, are almost always
insulated, not connected with each other; the bones, the muscles of
animal and organic life, the cartilages, the fibro-cartilages, the
medullary organs, the glands, the serous membranes, the hair, &c.
exhibit this insulation in a remarkable manner. Each portion belonging
to these different systems, has always between it and the other
portions of the same system many intermediate organs, which are of a
very different nature, and which consequently belong to other systems.
There are hardly any except the cutaneous, fibrous and mucous systems,
which are everywhere continuous in their different parts; yet this last
has no communication between that portion of it which is spread upon
the digestive and respiratory apparatus, and that which belongs to the
urinary and genital organs.

We have seen on the contrary that the primitive systems are everywhere
continuous, having no interruptions in them. The cellular, the
arterial, the venous, the absorbent, the nervous are so arranged, that
if it were possible to remove all the organs they enter, and leave them
alone, they would form a complete whole, formed differently according
to the different systems. The exhalants can also be considered as
everywhere connected, as we have seen. Suppose on the contrary that the
organs intermediate to the bones, the cartilages, the fibro-cartilages,
&c. should be removed, all the parts of these systems would
immediately be separated, and you would not have one continuous whole.

The order to be followed in the examination of these systems is of no
importance; we shall place them in the following order, which will
comprehend 1st, the osseous; 2d, medullary; 3d, cartilaginous; 4th,
fibrous; 5th, fibro-cartilaginous; 6th, animal muscular; 7th, organic
muscular; 8th, mucous; 9th, serous; 10th, glandular; 11th, cutaneous;
12th, epidermoid; 13th, and finally, the system of the hair.

Observe that nature is not confined to any methodical order, in
distributing these systems in the different apparatus; that she has
no regard to the great differences that she has established between
the functions. Each can at the same time belong to the apparatus of
functions that have no analogy. Thus the fibro-cartilaginous, which
is found especially in the organs of locomotion, and consequently in
animal life, enters also by the trachea into the respiratory apparatus;
thus the mucous system, everywhere destined to the organs of internal
life, belongs also to the external life in the conjunctiva, in the
nasal fossæ, &c. to generation in the vesiculæ seminales, in the
prostate, &c.; thus the glandular system pours by turns fluids upon the
organs of the two lives as upon those of generation; thus the serous
surfaces are spread upon parts whose functions have no resemblance
upon the brain and the stomach, for example, upon the articular
cartilages and the lungs, &c. Let us consider then the simple systems
abstractedly, if I may so say; let us describe them in an insulated
manner as materials distinct from each other, though united two by
two, three by three, four by four, &c. to form the partial edifices of
our apparatus, edifices from which results the general edifice of our
organs. Each of these apparatus is destined to exercise a determinate
function, and ought consequently to be classed as functions; it is in
this manner also that we shall distribute them in the Descriptive
Anatomy. But the simple systems, not tending to a common object, except
as they are united in the apparatus, we cannot, when considering them
separately, confine them to any classification borrowed from their
destination.



OSSEOUS SYSTEM.


This system, remarkable among all the others by the hardness and
resistance that characterize it, has from this double attribute a
fitness to serve as a common base for all, upon which they rest, and
around which they are suspended and fixed. The whole of the pieces that
form it, are connected together for this use, by means of flexible and
resisting bands, which with these pieces make a whole that is called
a skeleton. The osseous whole, placed in the midst of many organs
that it sustains, everywhere continuous in its different parts, has
not however, like the primitive systems, continuity of peculiar life
from one of its extremities to the other. The bands which connect
these different pieces, very different from them in their nature and
their properties, produce in them an insulation of vitality, which the
different parts of the above systems do not exhibit, because in their
continuity their nature is everywhere the same.


ARTICLE FIRST.


_Of the Forms of the Osseous System._

Considered in relation to their forms, the bones are of three sorts,
long, flat and short. One dimension predominates in the first, viz.
length; two are in nearly equal proportions in the second, length and
breadth; these two last dimensions, with thickness especially added,
characterize the short bones. Let us examine each in a general manner.


I. _Of the Long Bones._

The long bones belong in general to the apparatus of locomotion, in
which they form a kind of levers that the muscles move in different
directions. All are placed in the extremities, in which their whole
forms a kind of central column, moveable in different directions. We
see them successively diminishing in length and increasing in number,
when examined from the superior to the inferior part, from the thigh
or the humerus to the phalanges of the toes or the fingers. It follows
from this double opposite arrangement, that the top of the limbs is
characterized by the extent of its motions, and the bottom by the
multiplicity, variety and narrow limits of these motions.

These bones have all an analogous conformation; thick and large at
their extremities, they are more slender and usually rounded in the
middle or body, as anatomists call it.

The size of the osseous extremities exhibits the double advantage, 1st,
of presenting to the articulations large surfaces and consequently more
causes of resistance to different displacements; 2d, of contributing
to the regularity of the forms of the limb to which they belong.
Observe in fact that the muscles and the bones are placed in an inverse
direction in the extremities. The middle of the first, which is their
largest part, corresponds to the middle of the second, which forms
their small portion, whilst the extremities of these compensate by
their size for the smallness of the tendons which terminate the others,
and which are placed at the side of them. The increase of size of the
extremities of the long bones is not sudden; it commences imperceptibly
upon the body. We observe upon these different extremities eminences of
articulation and of insertion.

The middle or the body has no eminence; prominent lines are seen
there, always destined for aponeurotic insertions, and which, when
they are very considerable take from the bone its cylindrical form,
which it however preserves in the interior; thus the tibia is evidently
triangular externally, though within its canal has the form of that of
the femur. In general these lines of insertion, always separated by
plain surfaces, are three in number upon each long bone, as we see on
the humerus, the radius, the ulna, the tibia, fibula, &c. I know not
the reason of this law of conformation. Another general observation
is, that the body of almost all the long bones is twisted, so that the
direction of its superior part is not the same as that of the inferior;
by tracing from above downwards one of these lines of which I have just
spoken, this may be seen; it is however more evident in the adult than
in the fœtus. This change of direction has no uniformity in the course
it pursues.

The internal forms of the long bones are very well seen by sawing them
longitudinally. The texture of the cells fills them to the extremities;
it is, as we shall see, more fine and less abundant in the middle,
where the medullary canal exists.

This canal does not exist in the first month of the fœtus, nor as long
as the bone is cartilaginous; the osseous state is the period of its
formation. All the gelatine of the middle of the bone is then absorbed,
exhalation brings no more there, except in the very delicate texture of
the cells that this canal contains; this function, which is nothing in
the centre, becomes more active on the circumference of the bone. This
increase of activity of the external exhalants favours the formation
of the compact texture, the development of which takes place precisely
at the same time as that of the canal whose parietes it forms; so that
at this period of ossification, exhalation and absorption appear to be
in an inverse state in the two parts of the bone; one is very active on
the exterior in bringing phosphate of lime, with which it encrusts the
already existing parenchyma; the other is very active in the interior
in removing the gelatine whose absence forms the space from which the
medullary canal arises.

There is no well marked medullary cavity except in the humerus, the
radius, the ulna, the femur, the tibia, the fibula and clavicle. The
ribs and the phalanges, which in their forms resemble them, have much
of the ordinary texture of the cells in their centre, and hardly
ever any of that more delicate texture of the cells which occupies
the centre of the bones above named, and which is only found in the
medullary cavity.

This cavity does not extend beyond the body of the bone; where the
compact texture grows thinner, it disappears, and is replaced by a
great quantity of the texture of the cells, which fills the extremity
of the bone. Its form is cylindrical and its direction straight. It
does not vary in its form, on account of its asperities or the external
prominent lines of the body of the bone, which is only thicker in
these places. Its parietes are much smoother in the middle, than at
the extremities, where there are already many considerable cellular
filaments thrown off. There are in many subjects, delicate, horizontal
bony partitions, which interrupt almost entirely its continuity in this
place, and appear to divide it into two or three very distinct parts.

The medullary canal serves not only to lodge and defend the medullary
organ, but also to give more resistance to the bone; for we know, that
of two cylinders formed of an equal quantity of matter, one of which
is hollow, and consequently has a greater diameter than the other
which is full, the first will resist more than the second, because we
can bend and break it with less facility. Full cylinders, equal in
diameter to the long bones, would have prevented by their weight, the
motions of the limbs; whilst other cylinders of the same weight as the
present, but without any cavity, would give too small a surface for
the insertion of the muscles. To unite small weight with a sufficient
space in the middle of the long bones, is then a great advantage of the
medullary canal.

This canal disappears in the first periods of the formation of callus
in fractures, because the whole medullary organ is occupied at this
place by gelatine, and becomes cartilaginous; then this gelatine
gradually re-absorbed, without being replaced, favours the development
of a new cavity, and the communication is re-established between the
superior and inferior parts of the canal.

I have observed that, in the first age, and while the extremities
of the bones are cartilaginous, the medullary canal is shorter in
proportion than in the adult; it hardly forms at birth more than the
middle third of the bone, the superior and inferior thirds being formed
at first by the cartilaginous portion of each extremity, then a texture
of cells intermediate between this portion and the canal; so that as we
advance in age, its length becomes in proportion greater.


II. _Of the Flat Bones._

The flat bones have in general, but little relation to locomotion,
which they only assist by the insertion of the muscles that go to the
long bones. Nature designs them especially to form the cavities, such
as those of the cranium and the pelvis. Their conformation renders them
very proper for this use. Their number varies according to the cavities
with which they are connected; many always unite to form one, and it
is this circumstance that contributes in part to their solidity. In
fact, external blows losing their force at the place of their junction,
fracture them with less ease. If the cranium was only one single
piece, its solutions of continuity would be much more frequent than
they now are. So that as the sutures ossify in old age, they become
more brittle. In children, in whom the ossification is not complete,
and the number of whose separate, osseous pieces is consequently more
considerable in the head, the pelvis, &c. the difficulty of fractures
is very great, because the soft bands which unite the solid parts yield
to external bodies, without breaking.

The flat bones are almost all curved, concave and convex on the
opposite sides; this arises from their destination in the formation of
cavities. Their curve varies according to the place in the cavity they
occupy; this curve is the cause of a very powerful resistance, when
that mentioned above does not exist. Thus in the first age, the cranium
resists by yielding; but as the sutures become more closed, and only
one osseous piece is formed, it is by the mechanism of the arch that
the brain is protected.

All the flat bones have two surfaces and a circumference. According
as the first serve for muscular insertions, or are only covered by
aponeuroses, membranes, &c. they are rough or smooth. Towards the
middle the bone is thinner; it has more thickness at the circumference,
which is either for articulation or insertion. In the first case, this
excess of thickness gives more solidity to the joints, which are then
made with larger surfaces, as we see in the cranium; in the second, it
presents to the fibres more points of origin, as we see on the crista
of the ilium and the greater part of its circumference.

The internal forms of the flat bones have but few peculiarities; their
two external layers leave between them a space which is filled by the
texture of the cells.


III. _Of the Short Bones._

The short bones are placed in general in parts where are found united
mobility and solidity, as in the vertebral column, the tarsus, and the
metatarsus. Always small, they are in great number in the regions which
they occupy; their number compensates for their size in the formation
of the parts of the skeleton to which they contribute. It is this
number also, that gives to these parts the union of the two almost
opposite attributes of which we have spoken, viz. solidity, because
the external efforts are lost in the numerous bands which unite them,
and mobility, because the whole of their individual motions gives a
considerable general motion.

There is nothing constant or uniform in the external conformation
of these bones; it is modified according to the general plan of the
whole, of which they are the parts; thus the different uses of the
carpus, metacarpus and vertebral column determine the different forms
of their respective bones. These bones have always many cavities and
eminences upon their external surfaces, necessary for their numerous
articulations, for the insertion of the many ligamentary cords that
unite them, and the muscles that move them.

In the interior, these bones have nothing peculiar, except an abundance
of the texture of the cells which forms them almost wholly, and exposes
them to frequent caries.

Nature is not however regular in the division of bones into long,
flat and short. Here as elsewhere, she disregards our methodical
descriptions, and shows us the bones sometimes exhibiting the character
of long ones and short, and sometimes uniting the attributes of both
these last with the flat ones. The basilary apophysis and the superior
part of the occiput, the body and the lateral portions of the sphenoid,
when placed in contrast, prove this assertion. A bone sometimes by
its external form belongs to the long ones, but from its internal
organization should be classed with the flat, of this the ribs are an
example, &c.


IV. _Of the Bony Eminences._

The bony eminences have generally the name of apophyses; they are
called epiphyses when the cartilage of ossification which unites them
to the bone is not yet encrusted with calcareous substance.

These eminences have four great divisions; viz. those, 1st, of
articulation; 2d, of insertion; 3d, of reflection; 4th, of impression.

1st. The eminences of articulation vary according as the articulation
is moveable or immoveable; I shall not consider them here, as I should
be obliged to repeat it in the chapter upon articulations.

2d. The eminences of insertion are very numerous in the bones; they
only give attachment to the fibrous organs, as the ligaments, the
tendons, the aponeuroses, the dura-mater; no organ differing from these
is implanted into the bony eminences, or generally into the bones,
except by means of them; the muscles are a remarkable example of this.

These eminences are usually much less in women than in men, in children
than in adults, in weak animals than in carnivorous ones who live by
attacking and destroying their prey. The prominence of the eminences of
insertion is always an index of the force and vigour of the motions.
They are the more developed in proportion as the muscles are. Examine
comparatively the skeleton of a strong, sanguineous man, whose muscles
are powerfully delineated through the integuments, and that of a
feeble, phlegmatic man, whose rounded forms like those of women, do not
appear prominent, and you will see the difference.

The form of these eminences of insertion varies greatly; sometimes the
muscles are inserted by many separate aponeurotic fibres; then they
are small, very numerous and form only little asperities imprinted on
a greater or less surface; sometimes it is by a single tendon that the
muscle takes its origin, then the apophysis is usually very prominent,
and occupies a small space. Sometimes a broad aponeurosis gives rise to
the fleshy fibres; it is then a bony line, more or less projecting that
gives insertion.

The eminences are in general in proportion to the muscles that are
attached to them; for example, in three muscles of nearly equal size,
one of which is attached by separate fibres, the other by a tendon, and
the other by an aponeurosis, we observe that the sum of the asperities
of insertion of the first, the separate apophysis of the second, and
the prominent line of the third are nearly equal in the quantity of
osseous substance that forms them; so that by supposing that the
apophysis was divided into asperities, or extended into a line, or that
the asperities were united together, or the line concentrated so as to
form an apophysis, this quantity of osseous substance would be found to
be about the same.

We understand all the advantage of the eminences for the insertion of
muscles, which they render distant from the centre of the bone, lessen
the parallelism with its axis and consequently favour their motions in
an evident manner.

Are these produced by the pulling of the muscles? This opinion borrowed
from the laws of the formation of soft and inorganic bodies, does not
accord with the known phenomena of vitality, with the existence of
eminences where there is no muscular insertion, and which are often
more prominent than these, with the disproportion that exists between
the elongation of certain apophyses by muscular insertion, that of the
styloid, for example, and the force of the muscles that are attached to
it, &c.

The eminences for ligamentary insertion have the advantage, by removing
a little the ligament from the articulation, of facilitating its
motions; this is especially remarkable in the lateral ligaments of the
elbow, the knee, &c.

As to the other eminences of insertion, we can hardly consider in a
general manner their respective functions.

3d. The eminences of reflection are those under which a tendon
passes, in deviating from its primitive course; such is the hook of
the pterygoid apophysis, the malleolar extremity of the fibula, &c.
Almost all these eminences have a slope or excavation in one direction,
connected in the opposite with a ligament, so as to form a ring for the
passage of the tendon.

4th. The eminences of impression are those which arise, when the
different organs form on the osseous surfaces excavations that
separate these eminences, which in fact only appear because the bone
at this place remains at its ordinary level. The cerebral and muscular
impressions are given as examples of this arrangement. But are these
impressions really the effect of the compression of the organs on the
bone, or do they arise from the laws of the osseous development, laws
which give to the bones forms accommodated to the surrounding organs? I
adopt more readily the second than the first of these opinions, which
has been thought very probable from the effect of aneurisms upon bones
that are contiguous to them, which are worn and gradually destroyed
by them. But let us remark that if the muscles, the brain, and the
vessels by their pressure, had upon the bones in a natural state, an
action analogous to that of aneurism, the state of the parts ought to
be the same as in that case. The compact layer ought to be destroyed
where these depressions are, and leave in its place an unequal, ragged
surface, but the contrary happens, which makes me think, that what is
commonly called the impression of organs, is only a natural effect of
ossification.


V. _Of the Osseous Cavities._

The osseous cavities are very numerous; those only which are found
on the exterior of the bones will be treated of. They are divided,
like the eminences, into articular and non-articular. The first
will be examined, with the analogous eminences, in the chapter on
articulations. Among the second there are cavities, 1st, of insertion;
2d, of reception; 3d, of slipping; 4th, of impression; 5th, of
transmission; 6th, of nutrition.

1st. The cavities of insertion give attachment to the aponeuroses of
the muscles, to the ligaments, &c. They have the advantage, 1st, of
multiplying the insertions of the fibres, without increasing the size
of the bone, since a concave surface is evidently more extensive than a
plain surface would be which should occupy the space between its edges;
2d, of allowing the muscular fibres more room, and consequently giving
them greater length than if they arose from an eminence, which also
gives more extent to the motions. The pterygoid, digastric cavities,
&c. present examples of this arrangement.

2d. The cavities of reception are those which serve to receive an
organ, lodge and defend it; such are the fossæ of the bones of the
cranium, those of the ossa ilii, &c. These cavities sometimes belong to
the whole of the bone, the form of which is concave, as we see in the
frontal bone, sometimes they are hollowed out upon an insulated part,
like the maxillary depression of the inferior jaw; they are always
destined for an essential part, for a gland, a viscus, &c.

3d. The cavities of slipping are in general found at the extremity
of the long bones. They are grooves, more or less deep, in which the
tendons glide to go to the place in which they are inserted. All are
covered with a cartilage and terminated by a very strong ligamentary
ring. Do the tendons by their friction form these cavities? This is
the common opinion, but it does not appear to me more probable than
the theory of muscular, vascular impressions, &c. These cavities
ought to be then so much the deeper, in proportion as the muscles
are the more exerted; they ought not to exist in subjects paralytic
from their infancy; they ought not to exist in the cartilages of
ossification in the fœtus, whose limbs have hardly ever moved; but the
contrary of all this is constantly observed. Let us describe then all
the different configurations of the bones, as a consequence of the
laws of ossification, laws in obedience to which the osseous forms,
all primitively determined, are made to develop. The size of the
extremities of the long bones favours the existence of these different
cavities, which cannot on this account injure the osseous solidity.

4th. The cavities of impression correspond with the eminences of the
same name. I have spoken of them above.

5th. The cavities of transmission are especially destined for the
vessels and the nerves. We find many of them on the head; they have
sometimes the form of a groove, sometimes that of a tube and at others
that of a slit, according to the thickness or breadth of the bones
which these vessels or nerves traverse in order to go from one place to
another. The periosteum lines them; they contain more or less cellular
texture. The nerves and vessels they transmit are foreign to the bones.

6th. The cavities of nutrition, on the contrary, give passage to
vessels which carry to the bones or the medullary organ the substances
that repair them. They are of three sorts.

The first form canals that are seen on the long bones exclusively,
and go to the medullary cavity. Each bone has but one of these,
situated always on its body, directed obliquely between the fibres of
the compact texture, running sometimes from below upwards, sometimes
from above down into the cavity of the bone, and thus forming a
communication from without to within for the vessel of the medullary
organ. This foramen serves particularly for the exhalation and
nutrition of this organ, and nourishes the bone only secondarily.

The second kind of cavities of nutrition belong especially to the
texture of the cells of the bones. Thus they are seen wherever
this texture abounds, in the extremities of the long bones, the
circumference of the flat ones, and the whole superficies of the short
ones. Their diameter is greater than that of the canal which goes to
the medullary cavity; it is less than that of the canals of the compact
texture. Their number is very considerable; I have counted a hundred
and forty upon the tibial extremity of the femur, twenty upon the body
of one of the dorsal vertebræ, fifty upon the os calcis, &c. In general
this number is always in proportion to the quantity of the texture of
the cells that the bone contains. Hence why there are but few on the
flat bones of the cranium, why they are more numerous on the flat bones
of the pelvis especially where this texture is abundant, as on the
ischium, on the iliac portion of the circumference of the ilium, &c.
By pouring mercury into the spongy texture, it runs out from all these
foramina, and thus proves their communications. They are irregularly
scattered wherever they are. They are not met with on the body of the
long bones, because the body contains little or none of the texture of
the cells.

The third kind of canals of nutrition is only destined to the compact
texture. It consists of an infinite number of little pores which the
eye can clearly distinguish, and through which small vessels pass, that
go to this texture. An evident proof that they do not go to the texture
of the cells, is, that in the preceding experiment, the mercury never
finds in them a way to escape externally. It is impossible to determine
their number; it is prodigious in childhood. As the bones in old age
become filled with calcareous substance, they are obliterated, and
the vessels they contain become small ligaments, foreign to osseous
nutrition, which continually grows weaker, and is soon annihilated,
and allows necrosis to seize upon the bones, if general death does not
prevent this partial death of the osseous system.


ARTICLE SECOND.

ORGANIZATION OF THE OSSEOUS SYSTEM.

The peculiar texture of the osseous system forms in it the principal
and predominant part, especially as we advance in age. The common
organs are in much less proportion.


I. _Texture Peculiar to the Osseous System._

The texture of the bones, like that of most of the other organs,
presents itself under the aspect of fibres whose nature is everywhere
the same, but which differently arranged, form two principal
modifications; in the one, these fibres being more or less scattered,
exhibit many cells; in the other being close to each other, they form a
compact substance in which it is difficult to distinguish them. Hence
two sub-divisions of the osseous texture, that with cells, and the
compact. Authors admit a third one, the reticular; but this is included
in the first.


_Texture with Cells._

The texture with cells does not exist in the first periods of
ossification. The time of its formation is when the phosphate of lime
is added to the gelatine of the primitive cartilage, and gives to the
organ the bony nature. Then an infinite number of cells is formed in
the solid mass of cartilage, because the gelatine, taken up by the
absorbents, disappears in the place they occupy. No more is brought
by the exhalants, which begin to carry the phosphate of lime to the
fibrous cross-pieces, whose interlacing forms these cells; so that
the development of the texture of the cells belongs evidently to the
disproportion that takes place in the bones at a certain period of
their growth, between the functions of the exhalant and absorbent
system, until then in equilibrium. We know not the cause of this
disproportion, it appears to be a law of ossification. It is by virtue
of this law and by an analogous mechanism, that the os ethmoides, at
first solid and full when it is cartilage, is hollowed out at the
period of its ossification, into a great number of cells. It is thus
that the sphenoidal, frontal sinuses, &c. are formed and enlarged.

The formation of the texture of the cells ceases when all the epiphyses
have disappeared. At this period it exhibits to us an infinite number
of fibres which appear to arise from the internal surface of the
compact texture, go in different directions, cross, unite, separate,
bifurcate, in a word, pursue such irregular courses, that it is
impossible to follow them. Their size is not less variable; sometimes
their delicacy is such, that they can hardly be touched without
breaking; at others they are quite large. Often instead of fibres there
are layers, of more or less considerable size, from which arise other
smaller ones, which appear to ramify, and from which result, when
they are near each other, species of canals, which are seen very well
by sawing transversely the extremity of a long bone, so as to have a
segment of half an inch.

The cells which are made by their separation, are of very unequal form
and capacity.

All communicate together; the following experiments prove this. 1st.
If we make a hole in the extremity of a long bone, or upon the surface
of a short or flat one, and pour in mercury, it passes through all the
communications, and comes out of the natural foramina on the surface
of the bone, which also open into the cells. 2d. Saw a long bone at one
of its extremities, cover its whole surface with something that shuts
up its pores, then expose it to the sun; the medullary fluid not being
able to escape by the external pores, will come out at the sawed place,
after passing successively through all the cells. 3d. By varnishing a
dry bone, and opening it only in two opposite points, we can force air,
water and every kind of fluid through these communications, from one
opening to the other.

We can then consider the interior of every bone as forming a general
cavity that is filled by many interlaced fibres. I have not observed a
sensible difference in the direction of these fibres in the three kinds
of bones.


_Compact Texture._

The fibres that form the compact texture are not the same as those
of the preceding. These fibres, being in juxta-position, not leaving
any space between them, giving by their approximation a remarkable
density to the texture they form, have a longitudinal direction in the
long bones, are in the form of rays in the flat ones, and cross each
other in all directions in the short ones. This triple arrangement of
the fibres of the compact texture appears to be wholly owing to the
manner of ossification. In fact, when we examine its progress in the
primitive cartilages, we see these organs encrusted with the phosphate
of lime, in the same direction which these fibres afterwards take.
Thus these fibres are very evident in the first age, on the bones of
the cranium in particular. When the phosphate of lime, successively
deposited on the cartilaginous parenchyma, predominates there, then
the whole is confounded in the compact texture in one homogeneous
mass. But still there are different circumstances that indicate the
primitive direction of the fibres: 1st. When by an acid we remove from
bones their calcareous part, then the cartilaginous portion keeps as a
kind of mould, the form of the substances that filled it, and exhibits
fibres whose direction is the same as that pointed out for the three
species of bones. If we wish to separate the cartilaginous layers, it
is in this direction that it is most easily done. 2d. The fissures that
come in bones long exposed to the air follow in general the natural
direction of the fibres. 3d. Calcined bones exhibit nearly the same
phenomenon.

The direction of the fibres of the compact texture is changed entirely
in the apophyses, in which it does not follow that of the principal
bone. In those, which by their form, partake of the character of the
long bones, as in the styloid, these fibres are longitudinal; they
go in all directions in those, which like the mastoid, the different
species of condyles, &c. resemble in their shape the short bones.

The assemblage of the fibres forms, according to anatomists, layers
which they have considered as in juxta-position, and held together
by little pins according to some, and by the interlacing of fibres
according to others. These osseous layers do not appear to me to exist
in nature. All the fibres of the compact texture adhere to each other,
cross and form a whole that we cannot conceive of in this manner, and
which besides does not accord with the irregularity of the distribution
of the vessels. Art separates here fibres layer by layer, as it is
done in a muscle, in a ligament, &c.; but these layers are wholly
factitious; to exhibit the bones as formed by an union of these layers
is to give a very inaccurate idea of their structure. It is still
more inaccurate to consider these layers as attached to each other by
osseous pins, by attraction, or by a glutinous matter which serves as
a glue. All these ideas, contrary to anatomical examination, suggested
by a false application of the laws of the adhesion of inorganic bodies
to the adhesion of organized fibres, now belong only to the history
of physiological errors. There is a circumstance, it is said, that
very evidently proves the lamellated structure of the bones, it is
their exfoliation. It is true that often very distinct layers are
separated from the living bone, but these layers are only the product
of exfoliation itself. Then in fact the bone dies on the surface;
the superficial vessels receive no more blood; this fluid is stopped
under the portion deprived of life, the exhalation of the phosphate of
lime ceases there, every kind of sanguineous, exhalant and absorbent
vessel is destroyed; a slow inflammation, with suppuration, comes on,
and fixes the line of demarcation; and as this line is often at the
same place, all which is above it becomes an inorganic layer which
gradually falls off, and preserves its osseous solidity, because the
dead absorbents were not able to remove the phosphate of lime. Besides,
nothing is more common than to see exfoliation take place not by
layers, and the bone afterwards exhibit an unequal surface, the effect
of the inequality of the thickness of the exfoliated portions. Finally,
exfoliation often takes place in a direction opposite to that which the
layers are thought to have; this is what we see in the separation of
the extremity of the long bones, that have been exposed to the air or
too much irritated after amputation, in the shedding of the horns of
animals, &c. Let us consider the compact texture as an assemblage of
condensed fibres, not separated by layers, which we can only consider
as imaginary.

The fibres of the compact texture differ in their organic arrangement,
from the muscular fibres in this, that frequent elongations unite them
to each other, whereas the muscular have only the cellular organ, the
vessels and the nerves as the means of union. Such is the intimate
juxta-position of the fibres of the compact texture, that they leave
between them only pores hardly sensible to the naked eye, but which
become so however with a glass, and which the medullary juice and
vessels fill. In the rickets this density of texture disappears, and
we observe in the middle part of the long bones and under the layer of
periosteum more thick than common, an osseous texture, easily bent in
all directions, forming an infinity of cells and taking the place of
the compact texture that ought to be there. It appears that this change
of compact texture into that of cells is made less by the absorption of
a part of the phosphate of lime, than by the extension of the osseous
fibres which separate from each other, and leave between them spaces
that did not before exist; this gives to the bodies of long rickety
bones a very considerable thickness. I have many times made this remark.


_Arrangement of the two Osseous Textures in the three kinds of Bones._

The osseous textures, considered in the different kinds of bones, are
differently arranged. In general the compact forms the exterior, the
covering of the bone, and that of the cells occupies the interior. The
ossa spongiosa form an exception to this rule, the modifications of
which we shall now examine.

1st. In the long bones, the compact texture has a very remarkable
thickness in the centre, where it serves the triple purpose, first
of protecting the medullary organ, of which it is the covering,
then of giving solidity to the bone in this place, which more than
the extremities, is exposed to great efforts in locomotion, falls,
concussion, &c. and where the bone, traversed only by some very weak
fibres of the cells, cannot borrow its resistance but from its external
parietes; finally, of thus diminishing without danger the size of the
bone in the middle part of the limb, the form of which, becomes by
this means much more regular. So that as we go from the centre, we see
in a long bone, sawed longitudinally, the compact texture diminish
in thickness, and form at last at the extremities only a delicate
layer analogous to that which covers the short bones. Thus the power
of resistance of the long bones, at their extremity, is less in their
compact shell, than in the great quantity of the texture of the cells
deposited under it; it is this especially that prevents fractures;
hence we see how the proportion of the compact texture and that of the
cells being inverse in the two parts of the bone, the manner of their
resistance is also inverse.

The texture of the cells differs a little when examined in the
medullary canal and in the extremities. In the canal there are
extremely delicate filaments, continued from larger fibres which fill
above and below the extremities of the bone, and the compact portion
which forms the osseous cylinder. Few and scattered at random in the
middle of the canal, these filaments approximate each other, and form
a kind of net-work, as they go from it; hence the name of reticular
substance by which it is designated. But it is not a distinct texture,
it is only a modification of that of the cells; a modification, which
is especially characterized, 1st, by the delicacy of the fibres; 2d,
by the uniform absence of those fine and short layers which frequently
belong to this texture in other parts. Besides, the manifest use of
this portion of the texture of the cells, too weak to contribute to
the resistance of the bone, is evidently to serve as a support to the
medullary system, and insertion for its membrane. At the extremities
of the long bones, the fibres of the texture of the cells increase
a little, approximate each other, are scattered in layers, and give
to the bone by their union and number, a remarkable thickness and
resistance, without however increasing the weight, which very much
favours locomotion, considering that this weight placed at the
extremity of the lever would have been very painful to raise.

2d. In the flat bones, the compact texture forms two external layers,
the thickness of which is between that of the middle of the long bones,
and that of the extremity of the same bones, or that of the short ones.
Between these two layers is found the texture of the cells, similar
in general to that of the extremity of the long bones, a little more
lamellated however, thicker usually at the circumference, often almost
wanting in the middle of the bone, where its two compact layers in
juxta-position allow a light to be seen through it, when placed behind.
In general wherever the broad bones are so thin, from the want of the
texture of the cells, there are very strong muscles, which by their
thick layers give solidity to the bone. We see examples of this in the
iliac, sub-scapular, inferior-occipital fossæ, &c.

3d. In the short bones, the texture of the cells always predominates;
the bone is almost wholly formed of it, a delicate layer of compact
texture forms only its covering, and in this respect, the organization
of these bones is the same as that of the long bones at their
extremities; thus the resistance of the bone depends on the whole of
its mass, and no part makes a greater resistance than another against
fractures. We see, from all that has thus far been said, the successive
manner of the solidity of the different bones. In the middle of the
long bones, there is hardly any thing but compact texture to which it
is owing; in the flat bones it is as much to this texture as to that of
the cells; in the extremities of the long bones and in the short ones
it is almost to this last only that its solidity is owing.

4th. In the osseous eminences, the compact texture is more abundant
than elsewhere, especially in those of insertion, as in the prominent
lines of the long bones, which are all formed of it, in the asperities
of the osseous surfaces, in their angles. If the eminence is
considerable, there enters into it also more or less of the texture
of the cells as we see in the spinous and transverse processes of the
vertebræ, in the coracoid, mastoid, &c. processes. The eminences of the
moveable articulations have in general less of the compact texture,
solidity is given to the bone by the articular cartilage. Those of the
immoveable articulations, on the contrary, in general smaller, as the
sutures of the bones of the cranium, for example, are in proportion
more compact than cellular.

5th. In the osseous cavities, all those which serve for moveable
articulations, are only furnished with a very delicate compact layer;
it is thicker when the articulations are immoveable. In general all
the foramina, cavities and canals that transmit from one region to
another vessels, nerves or other organs are everywhere lined with a
compact layer that defends them from the impression of these parts.
The foramina at the base of the cranium, the dental canals, the vidian
foramina, &c. are examples of this arrangement.


_Of the Composition of the Osseous Texture._

Whatever may be the modifications under which it is exhibited, the
osseous texture has everywhere the same nature; the same elements form
it; now these substances are especially a saline calcareous substance
and a gelatinous one.

The existence of the saline substance in the bones is proved in
different ways. 1st. Combustion, by destroying the gelatinous portion,
leaves a friable, brittle body, of a form analogous to that of the bone
and which is nothing but this saline substance, which resembles, if
we may so say, a moulded body that keeps the form of the mould after
it has been taken away. If the combustion is pushed very far, and a
red heat produced on the calcined bones, they undergo a semi-fusion,
which makes them resemble the state of porcelain; they have then a
very compact, fine, semi-vitreous grain, a semi-transparency, and an
appearance like that of the vitrified earths. 2d. The long continued
exposure of the bones to the air produces an effect very similar to
that of the first degree of combustion, though however the gelatine
is rarely so thoroughly removed, and the saline portion so perfectly
exposed as by the action of fire. Besides, it requires a very long time
to produce this effect, especially upon the thick bones; the thin ones
are more easily altered; I have often made this observation. After ten
years exposure to the air and rain, I have observed that clavicles
taken from the cemetery of Clamart, exhibited upon the action of the
acids, a cartilaginous parenchyma almost equal to that of a bone that
had been some time dried. But this parenchyma finally disappears, and
the bone falls to powder, when it is no longer supported by it, and the
particles of the remaining calcareous substance have been disunited
by time. 3d. In the last stages of all cancerous diseases, the bones
have a friability which is only owing to the greater proportion of this
last substance, a proportion arising itself from the small quantity
of gelatine that is then exhaled in the bones. 4th. When a bone has
been for some time exposed to the action of an acid, the nitric for
example, a portion of its substance is taken from it by this acid,
which is evidently a calcareous salt, as can be seen by mixing it
with a solution of an alkali, which uniting immediately to the acid,
exposes this salt, by making it precipitate. 5th. Papins digester, by
dissolving by the action of water reduced to vapour the gelatinous
portion, shows also this saline calcareous part.

Scheele has found that this portion is a neutral salt with an earthy
base, the phosphate of lime. Frequently the phosphorus in fresh bones
give them a luminous appearance, that can be seen very far in the
night. It is sometimes the whole of the bone, sometimes some parts only
that become luminous. I have always observed in the illuminated places
an oily exudation, either that comes from the medullary juice, or is
furnished by the fat of the neighbouring soft parts of the bone.

Different facts as evident as the preceding, prove in a manner not less
certain, the existence of a gelatinous substance in the bones. 1st.
When in the solution of the bones in the acids, the phosphate of lime
has left them, there remains a cartilaginous, flexible, elastic body,
yellowish when nitric acid is employed, of the same form as the bone.
Now we know that the gelatine especially nourishes the cartilages. 2d.
If besides we subject this cartilaginous residue to ebullition, we
extract a very great quantity of gelatine which is dissolved in the
water and can be afterwards precipitated by tannin. This substance
can even be removed from the bones without the previous extraction of
the phosphate of lime; it is thus that with bones stripped of every
surrounding organ, and reduced to very small fragments or even to
powder by the action of a rasp, very nourishing broths and jellies
are made. It is not without reason that in the preparation of boiled
meat, the bone is left attached to the meat; besides the white organs
that surround it, and the medullary oil that it contains, it furnishes
to the broth a substance that is peculiar to it. 3d. The combustion
of the bones, and especially of their cartilaginous residue, gives
an odour exactly similar to that of the combustion of the different
animal glues, which, as we know, the gelatine especially forms. 4th.
In the different affections in which the bones become soft, the earthy
substance is diminished more or less sensibly, and the gelatinous
remains more abundant in proportion than common.

These two substances, the gelatinous and saline, which enter
essentially into the composition of the bones, imprint upon them
very different characters. The phosphate of lime, almost foreign to
vitality, is only destined to give to the bones the solidity and
resistance that characterize them. The gelatinous substance, on the
contrary, has especially the animal character; thus the vital activity
is in the inverse ratio of one and the direct ratio of the other, as
we shall see. Deprived of gelatine, the bones are not capable of being
digested, they offer nothing for the gastric juices to act upon, they
cannot extract nutritive matter from them, because they act upon them
nearly as water does, which dissolves the gelatinous substance and
extracts it from the saline portion. Different animals that swallow
fresh bones for nourishment, would die from eating a calcined one; thus
the more the bones contain of this substance, the more nourishing they
are; those of young animals are on this account more proper to make
gelatinous broths, more suitable to be digested raw by the stomachs
of certain species, &c. If we expose a bone to the action of an acid,
so as to have only its cartilaginous parenchyma left, and afterwards
soften this parenchyma in boiling water, it becomes an aliment that can
be eaten.

Besides phosphate of lime and gelatine, the bones contain also some
saline principles, as the sulphate and carbonate of soda, &c. But this
proportion is too small to be noticed. Upon this point, I refer to
chemical books, especially to the great work of Fourcroy.


II. _Common Parts which enter into the organization of the Osseous
System._

The ancients ranked the bones among the white parts, among the tendons,
the cartilages, &c. It is sufficient however to examine the interior of
them to see, by the redness that distinguishes them, that much blood
enters them. This blood penetrates in three orders of vessels; one
belonging to the medullary cavity of the long bones, another to the
texture of the cells, and the other to the compact texture. These two
last orders distributed in the osseous texture, appear to be especially
destined to deposit the phosphate of lime; for in the cartilages of
ossification, the white vessels alone carry the gelatine; in other
cartilages it is the same; so that I think that this kind of vessels is
also destined in the bones which are perfectly formed to nourish their
cartilaginous parenchyma, whilst the red vessels belong more to their
calcareous portion.

Each medullary cavity has only one vessel, and only one foramen of
nutrition. This vessel has a diameter proportioned to that of the bone
which it penetrates, and in which it is divided immediately into two
branches, without permitting any ramification on the compact texture.
These go in an opposite direction to the two extremities of the bone,
ramify ad infinitum in the medullary organ, and their last branches
are lost in the commencement of the texture of the cells, where they
anastomose with the vessels of this texture; that which occupies the
medullary cavity under the name of reticular, and the internal surface
of the compact texture, receive also some branches. A vein everywhere
accompanies the artery, and follows the different distributions of it.

The vessels of the second order belong to the texture of the cells
of the long, flat and short bones; they are equal in number to the
foramina of this texture, and ramify on its cells; they communicate
with those of the marrow and of the compact texture. At death, the
small arteries in general remain full of red blood, which indicates
their course which their minuteness would conceal, and which injections
can rarely demonstrate with accuracy. The accompanying veins of these
arteries can hardly be seen.

The blood-vessels of the third order are only the last ramifications
of the arteries surrounding the bones, ramifications which enter in
great number the compact texture, and stop there. The existence of
these vessels may be proved in different ways. 1st. By detaching the
dura mater from the internal surface of the cranium, many small
sanguineous drops prove their rupture. 2d. By raising on a subject
of a middle age the periosteum, we make the same observation. I have
remarked that these experiments succeed especially on those that have
been drowned, or on animals destroyed by asphyxia, on account of the
great quantity of blood their vessels contain. 3d. If we fracture a
long bone in the middle, the compact portion, which forms the medullary
canal, exhibits small reddish striæ, which are nothing but these small
vessels still full of blood, and of which we thus discover a greater or
less number, according to the manner in which the blood was arrested in
the capillary system at the instant of death. 4th. The saw-dust of the
compact texture in living animals is red, though less evidently so than
that of the texture of the cells; a proof that these vessels have been
divided.

The vessels of the bones are very numerous in childhood; they diminish
in the adult, and become scarce in old age. The facility of the
formation of callus follows the same proportion in the different ages
of life. Often in affections of the osseous parenchyma they have a
remarkable development, which much exceeds their natural diameter.
Osteo-sarcoma, spina-ventosa, &c. exhibit this, which is much oftener
observed in cancerous tumours than any other.

These vessels communicate with each other by numerous anastomoses;
this is what we see especially in the long bones, between those of
the medullary organ and those of the texture of the cells. By these
communications, they mutually assist each other's functions. I have
seen the nourishing foramen of the tibia completely obliterated in a
body that I injected. A sort of cartilage filled this foramen; the
artery formed a real ligament. Yet its bifurcation in the medullary
canal was found very well injected, and besides no alteration appeared
in the nutrition of the medullary organ, which had probably received
as much blood as usual. I found nothing in the neighbourhood of
the foramen, which showed the cause of this obliteration, which an
exostosis, an affection of the periosteum, or an inflammation can very
easily produce.

On the other hand we know that very considerable osseous layers are
often taken from the extremity of the long bones by caries, which
consequently destroys all the vessels corresponding to these layers,
and yet the bone beneath lives, principally by the blood that it
receives by the extremities of the artery of the medullary organ. This
is nearly what happens to the long bones in the first age, in which the
cartilaginous extremities have not vessels of the second order, and in
which consequently almost all the blood comes from this same artery
of the medullary organ; thus it is much larger in proportion, and the
foramen which receives it much more considerable.

Nothing is yet known upon the systems of absorbent and exhalant vessels
of the bones, and we can reason upon this point only from analogy.
Besides the nutritive process evidently supposes them there.

As to their cellular texture, it appears to be almost nothing; we can
even say that in whatever place we break the compact fibres or those
of the cells, its filaments are not distinct; but it is their dense
and compact texture that conceals them from us. In fact, 1st, when
this texture is softened, and the bone has become flesh, as it is
called, the cellular texture is very apparent there. 2d. The fleshy
granulations, rising on places that have been fractured or laid bare,
are only the extension of the cellular texture which has too much
calcareous substance to allow it to be seen in the natural state.
3d. After having removed from a fresh bone all this substance by an
acid, I have sometimes observed cellular filaments by separating the
cartilaginous fibres which form the parenchyma that is left. 4th. When
we boil this cartilaginous parenchyma in order to extract the gelatine
from it, there remains portions of membranes which are evidently
cellular.

We cannot trace the nerves in the bones, the filaments that enter them
are so fine; I do not know that anatomy has any positive data upon this
point.


ARTICLE THIRD.

PROPERTIES OF THE OSSEOUS SYSTEM.


I. _Physical Properties._

The bones have very strongly marked physical properties. Solidity and
hardness are their peculiar portion; they derive these properties
from the phosphate of lime which penetrates them, thus they are
constantly increasing with age, because this substance becomes more
and more predominant. Elasticity is another physical property of the
bones, which is found combined with the two preceding, but which is
in an inverse order; as it is in the gelatinous substance, in the
cartilaginous portion of the bone that it resides, it is, like this
portion, greater in childhood. In old age, the bones lose entirely
their suppleness and elasticity; they break more easily. Elasticity
is more evident in the long and small bones, than in those which are
larger; the fibula bends and evidently goes back again, this the tibia
could not do without difficulty. It is not that the one is more elastic
than the other, but it is that its conformation is more favourable to
the development of this property.


II. _Properties of Texture._

Although the hardness and solidity of the osseous texture seem to be
opposed to every kind of extension and contraction, yet these two
phenomena and the properties of texture from which they arise, are
often very evident in it.

The extensibility of the osseous fibres is proved by the observation
of many diseases, for example, the spina-ventosa, the swelling of the
maxillary sinus when it contains a polypus, by the enlargement of
the bones of the cranium in hydrocephalus, &c. I would remark on the
subject of these different distensions, that often by the influence
of analogous causes, the bones which yield and are distended in the
above cases, are broken, worn and destroyed in others. A polypus of
the nose breaks through the naso-palatine partition, without having
first distended it; aneurism of the aorta does not bend the sternum
or the vertebræ, but it breaks through and destroys these bones.
Whence arises this difference from causes nearly the same? This is not
easily determined. The contractility of texture is very evident in the
bones, when the cause which distended the fibres is removed. We see
the alveoli contract, and become effaced, when a tooth has been drawn
from them. The diminution of the thickness of the jaw after cutting
the teeth arises only from the contraction of its fibres, which are
no longer distended as much, because the root is not so broad as the
crown, which had till then been wholly in the bone. The maxillary sinus
contracts when a fungus is removed from it, or pus is discharged from
the carious bone, &c. If death was not too soon the consequence of the
puncture of the head of hydrocephalic patients, I am persuaded that we
should see the bones gradually contract, and restore the cavity of the
cranium to its natural dimensions. When we remove the dead piece from
a long bone in necrosis, the new bone, formed on the exterior by means
of the periosteum contracts in an evident manner. In paralysis of the
optic nerve, its foramen becomes narrower. The orbit contracts when a
cancerous eye has been extirpated. I have dissected the carotid canal
in a dog whose carotid I had tied; there was no contraction because the
blood coming by anastomoses dilated the artery to the usual size.

This contraction of the bones, by means of the contractility of
texture, is not so sudden as that of the muscles, the skin, &c. when
they are no longer distended by a tumour, an aqueous collection, &c.
This arises from the difference of the organic texture, from the
rigidity of osseous fibres owing to the calcareous substance they
contain, &c. Thus the organic sensibility is less evident in them.


III. _Vital Properties._

The bones have hardly any animal properties in a natural state. Their
sensibility is nothing; the saw, the mallet, and the chisel act upon
their texture almost with impunity; an obscure feeling is the only
result of the action of these instruments; fire even can act upon them
without making the animal suffer much. But in a morbid state, the
sensibility is developed to the greatest extent; we know the horrible
pains that attend spina-ventosa, and those not less severe that caries
produces in certain cases. If a bone is inflamed, as for example the
sawed extremity of a stump after amputation, this bone which in a
natural state had borne, without transmitting any painful impression,
the action of the saw, becomes as it were a new sensitive organ, to
which the least touch is painful. The animal contractility is nothing
in the osseous system.

The organic properties give life to this system as to all the others.
The sensibility of this kind certainly exists in it; the fluids that
penetrate it are felt, and by virtue of this feeling, those are
appropriated to it which are proper for its nutrition. But is there
in the osseous system a reaction upon these fluids? are there those
insensible oscillations which compose insensible organic contractility?
Its hardness seems to prevent them. But yet the circulation is carried
on there; it performs a constant work, an habitual composition and
decomposition, which can hardly be conceived of without reaction on
the part of the osseous system. Besides this reaction is more slow,
more difficult on account of its structure; and hence without doubt
the slowness, of which we shall speak, in the vital phenomena of the
osseous system. Sensible organic contractility is foreign to it.


_Character of the Vital Properties._

The peculiar life of the bones is composed then of only two vital
properties, organic sensibility and insensible organic contractility.
From these two properties are derived all the vital phenomena
that these organs exhibit, inflammations, formation of tumours,
cicatrization of solutions of continuity, &c. This peculiar life is
remarkable in general, as I have just observed, when compared with
the peculiar lives of the other organs, by its slowness, by the tardy
concatenation of its phenomena. All things being equal as to ages, and
the different proportions of the earthy and cartilaginous substances,
inflammation is more slow there than in the other parts. Callus is
remarkable among the other cicatrices by the length of its formation;
compare an exostosis in its origin, its progress and its development,
with a tumour of the soft parts, a phlegmon for example, and you will
see the difference. Who does not know, that whilst suppuration often
requires only a few days in the other organs, it is whole months in
forming in the middle of the bones? Observe the difference that there
is between a gangrene of the soft parts, in which death takes place in
a short time, with caries and necrosis of the bones, in which a long
period elapses between disease and death of the part. In general we can
say, when inflammation exists in a bone, that it is chronic.


_Sympathies._

This character of the vital properties imprints an analogous one
upon the sympathetic relations of the osseous system with the other
systems. At first the animal contractility and the sensible organic
contractility cannot be put in action in these relations, as they do
not exist in the bones. The animal sensibility being developed in them
with difficulty and slowly by the diseases that essentially affect
them, the sympathies can be brought into action in them only in an
obscure manner. These sympathies then should act essentially upon the
organic sensibility and upon the insensible organic contractility, and
as these two properties are developed slowly, the different sympathies
should not be connected with the acute affections of the other organs,
and this is what is clearly proved by observation. In fact observe
that whilst many other systems respond with great quickness to the
acute diseases of an organ, this, as well as the cartilaginous,
fibro-cartilaginous systems, &c. remain then almost always in inaction.
Let the stomach, the lungs, the brain, &c. be the seat of a severe
acute disease, you see immediately many sympathetic phenomena arise in
the nervous, vascular, muscular, glandular, cutaneous, mucous systems,
&c. &c.; all seem to feel the trouble of the affected organ; each,
according to the vital forces that predominate there, exhibit different
phenomena, which are only aberrations, irregular developments of these
forces; in the animal muscular system, it is the animal contractility
which is especially raised; hence spasms and convulsions; in the
glandular, the serous, the cutaneous, the mucous, &c. the insensible
organic contractility and the organic sensibility principally
experience alterations; hence the different sympathetic derangements of
the secretions, of the sweat, of the exhalations; in the nervous, it
is the animal sensibility which is especially brought sympathetically
into action; hence the wandering or fixed pains in different parts;
in the organic muscular, it is the organic contractility which is
raised; hence the irregular motions of the heart, the stomach and the
intestines. In all the acute diseases of an organ there are always two
orders of symptoms, the one relative to the affected organ, as are the
cough, the pain in the side, the spitting of blood, the difficulty
of respiration, &c. in peripneumonia; the others purely sympathetic
and arising from the relations which connect the vitality of this
organ with that of all the others; now these last are often much more
numerous than the others.

Observe the bones in the midst of all that general sympathetic
derangement of the systems in which life is very active; they undergo
no alteration; their life, more slow than that of the other systems,
is not connected with these phenomena which have an acute character;
neither is that of the cartilages, the fibro-cartilages, the hair, the
aponeuroses, &c. All these systems, remarkable by the same character of
vitality, do not respond to the acute affections of the other systems;
they are not sympathetically affected, during these affections, at
least in an evident manner. Observe all the acute fevers; their
numerous phenomena have an effect only upon those systems in which
life is very active; those in which it is distinguished by an opposite
character, have uniformly no connexion with these phenomena; they are,
if we may so say, calm and tranquil in the midst of the tempest which
agitates the others. Let us take for example the different eruptions
that appear in fevers; it is upon the skin, the mucous surfaces, &c.
that they come; they arise during the fever and they disappear with it;
now the bones, the cartilages, &c. could not, from their kind of life,
admit of this sudden origin and disappearance.

It is then in the slow and chronic affections that we must seek for
examples of sympathies of the osseous, cartilaginous systems, &c. In
the first stages of the venereal disease, in which it is marked only
by acute symptoms, or in which at least its progress is not very slow,
as when it appears in buboes, in inflammations of the urethra, &c. it
has no influence upon the osseous system; it is only when it is of long
standing, when it has, as it were, degenerated, and become chronic,
that it makes the bones the seat of pains, of different tumours, &c.
Besides, I do not know, that we have yet thoroughly analyzed the
osseous sympathies. I have shown only their general character. We
shall understand them better, when we have given more attention to the
relation that there is in diseases between the affection of each organ,
and its kind of vitality.


_Seat of the Vital Properties._

The bones penetrated by saline substances which tend continually to
obey the laws of affinity and attraction, and to make these laws
predominate over those of sensibility and organic mobility, seem
to hold a middle place in living bodies, between these bodies and
inanimate ones. There is truly but one part of their osseous texture
which partakes of the vital phenomena, viz. their cartilaginous
substance; the other part or calcareous substance is foreign to them;
thus the proportion of each of these substances determines in the bones
their degree of life. In infancy, in which the first predominates, in
the early stages of the formation of callus, in which it is exclusively
found, in the softening of the bones in which it remains almost alone,
all the vital phenomena become more evident and more powerful. On the
contrary, as age accumulates in the bones the saline substance, as in
certain animals this accumulation takes place by the natural laws of
ossification in some external portions of the system with calcareous
base, as in the horns of stags, the shells of crustaceous animals,
&c. so life is, if we may so say, successively destroyed in the
bones; it becomes nothing, when this calcareous portion predominates
considerably; this is what happens in the necrosis which produces the
fall of the horns, the casting of the shells of crustaceous animals, &c.

Besides, that which shows the vital energy in an organ, is the
rapidity with which inflammation goes through its periods in it, and
the frequency of this affection, &c. Now in the bones inflammation
is so much the more rapid, in proportion to the greater quantity
of cartilaginous texture they contain; observe the periods of the
formation of the callus in the different ages, periods which are
determined by the duration of the inflammation necessary for its
formation, you will see that in infancy they are short, that they are
much longer in old age, and that often even consolidation does not take
place, whilst it is effected with facility in all the soft parts. The
general weakness no doubt of all the vital forces which takes place
from the effect of age is one cause of this slowness and this rapidity
in the formation of the callus at the two extreme periods of life;
but the different proportions of gelatinous and calcareous substances
contribute much to it also; for when we compare other cicatrices with
this, the cutaneous, for example, we see that age establishes in them
an infinitely less sensible difference as it respects the slowness and
rapidity of this reunion, than in the osseous system. The bones have
not sufficient life to inflame and unite, like the skin, the muscles
also exhibit this phenomenon in a very evident manner. I have seen
an old man, the neck of whose fractured thigh-bone remained a long
time without reunion, and in whom a wound of the face was healed very
speedily by the first intention.

Finally, there is a simple experiment that I have often made, and which
proves as well as the preceding facts, that the cartilage is truly
the animal part of the bone. We know that one of the great attributes
of animal substances, is to contract and exhibit the horny hardening
when burnt; now when the bone is penetrated with its earthy salt, it
has not this kind of combustion; deprived of this salt by an acid, the
cartilaginous parenchyma which remains burns in this manner. The flat
bones in infancy in which this parenchyma predominates, exhibits also
this phenomenon in burning; it forces the calcareous portion, which is
in small quantity to obey the impulse that it gives it, and turns it
in various directions; but in the adult in whom the calcareous portion
is the largest, the bone remains unmoved while the fire penetrates it,
and its whole cartilage is taken away, without its fibres being able to
obey their tendency to the horny hardening which combustion imprints
upon them.


ARTICLE FOURTH.

OF THE ARTICULATIONS OF THE OSSEOUS SYSTEM.

All the bones are united together, and thus form the skeleton. The
manner of their union varies, but whatever it may be, it is known under
the general name of articulation.


I. _Division of the Articulations._

All the articulations can be referred to two general classes. Mobility
is the character of the first, immobility that of the second.

One belongs to all the bones which serve for locomotion, to some of
those destined to internal functions, as the ribs, the lower jaw, &c.
The other is especially met with in the bones, the union of which forms
the cavities designed to defend the organs; this we see in the head,
the pelvis, &c.


_Moveable Articulations. Observations upon their Motions._

I divide moveable articulations into four kinds, the characters
of which are borrowed from the different motions they execute. To
understand this division, it is necessary previously to know the
motions of the articulations in general. These motions can be included
under four species, which are, 1st, opposition; 2d, circumduction; 3d,
rotation; 4th, sliding.

1st. The motion of opposition is that which is made in two opposite
directions, for example, from flexion to extension, from adduction
to abduction, and vice versa. This motion is extensive or limited;
extensive when it is made in all directions, first in the four named
above, then in all the intermediate ones; limited, when it only takes
place from flexion to extension, from adduction to abduction, &c. The
thigh in its articulation with the pelvis enjoys an extensive motion of
opposition. The tibia in its articulation with the femur has a limited
motion of opposition.

2d. Circumduction is the motion in which the bone describes a kind of
cone, the summit of which is in its superior articulation, and the
base in the inferior; so that it is found successively in flexion,
adduction, extension and abduction, or in abduction, extension,
adduction and flexion, according to the motion by which it begins, and
that moreover it goes through all the intermediate directions. Hence we
see that circumduction is a motion composed of all those of opposition,
and in which the bone, instead of moving from one direction to an
opposite one, as in the preceding case, moves from one direction to
another nearest to it, describing thus by its extremity a circle which
is the base of a cone of which I have spoken, and which is so much the
greater as the bone is so much the longer. We easily understand that
among the bones, those only whose motion of opposition is loose, enjoy
that of circumduction.

3d. Rotation is wholly different from the preceding motion. In this
there was locomotion, a moving of the bone from one place to another;
here it remains always in the same place; it only turns upon its axis.
The humerus and the femur enjoy this motion which is simple.

4th. Sliding belongs to all the articulations. It is an obscure motion,
by which two surfaces go in an opposite direction, by sliding as it
were upon each other. In all the other motions, this is met with; but
it often exists without them.

It is easy to understand, from these views upon the articular motions,
the division into genera of the class of moveable articulations. In
fact, there are articulations in which all the motions are united; in
others, there is no rotation; in many rotation and circumduction are
wanting, and opposition exists only in one direction; some have only
rotation. Finally, there are those in which rotation, circumduction and
opposition are nothing, and sliding alone remains.

Hence we see that nature moves here as elsewhere by gradation, that
from the most moveable articulations to those that are the least so,
there are different degrees of decrease, that she descends gradually to
the immoveable articulations, that she is finally reduced to the motion
of sliding alone, like that which exists at the carpus, the tarsus,
&c. There is even an intermediate one between sliding and immobility;
it is the articulation of the symphysis pubis; which can be considered
with that of the humerus as forming the two extremes of the series of
moveable articulations.

All the articulations of which I have spoken are with contiguous
surfaces; this is the general character of those which are moveable.
There is however an exception to this rule; it is the articulation of
the body of the vertebræ, in which there is continuity and mobility.
The symphysis pubis is also in part continuous in its surfaces, and yet
has sometimes obscure motions. Hence arises a division of the moveable
articulations, into those with continuous surfaces, and into those with
contiguous ones.


_Immoveable Articulations._

The immoveable articulations are sometimes with surfaces inserted into
each other, as the bones of the cranium, in which many projections and
depressions reciprocally receive each other; sometimes with surfaces
in juxta-position, as in the articulation of the temporal with the
parietal, the two superior maxillary bones with each other; sometimes
with implanted surfaces, as in the teeth.

All the different divisions that I have mentioned will be easily
understood by the following table; it is not the same as that which
I have given in my treatise on the membranes; I think it presents
a classification a little more useful in this, that it offers for
a characteristic two things essential to be known in all kinds of
moveable articulations, viz. 1st, the relation of the articular
surfaces which characterizes the orders; 2d, the number of motions
of each which distinguishes the genera. There are no orders in the
immoveable articulations because, except the relation of surfaces, the
articulations have not differences sufficient to occasion them to be
sub-divided.


_Table of the Articulations._

                 ┌ CLASSES.       ┌ ORDERS.    ┌        GENERA.
                 │                │            │1st. Extensive Opposition,
                 │                │            │ Circumduction and
                 │                │            │ Rotation.
                 │                │1st. With   │2d. Extensive Opposition
                 │                │ Contiguous │ and Circumduction.
                 │1st. Moveable.  │ Surfaces.  │3d. Limited Opposition.
                 │                │            │4th. Rotation.
                 │                │            └5th. Sliding.
  ARTICULATIONS. │                │2d. With Continuous
                 │                └   Surfaces.
                 │
                 │                ┌1st. With Surfaces
                 │                │   in juxta-position.
                 │                │2d. With Surfaces
                 │                │   inserted
                 └2d. Immoveable. │   into each other.
                                  │3d. With Surfaces
                                  └   implanted.

After having thus divided the articulations, let us offer upon each
class some general observations. But let us first remark that the
preceding table, considered in respect to the moveable articulations
with contiguous surfaces, indicates perfectly the disposition of these
articulations as to luxations, which are so much the more frequent as
the motions are more extensive. The first genus is the most exposed to
it, the last the least so; and the others are more or less so according
to their distance from the first.


II. _Observations upon the Moveable Articulations._

The class of moveable articulations is the most important to be
considered, because their mechanism is the most complicated of the two
orders composing this class, as we have seen. The latter, or that of
the articulations with continuous surfaces, will not be considered in
our general observations, as it embraces only one species of motion,
that of the vertebræ, this motion will be noticed in the examination
of the spine. The order of the moveable articulations with contiguous
surfaces, comprises, as we have said, five genera characterized by
their respective motions.


_First Genus._

Extensive opposition, circumduction and rotation characterize this
genus. The first by the extent and number of its motions. The
articulations of the humerus with the scapula and the femur with the
ilium are examples of it; they even exclusively compose it.

We see why it is at the superior part of the limbs that nature has
placed this genus. A double advantage results from this situation. On
the one hand, very far from the part of the limb immediately exposed
to the action of external bodies, it more easily escapes luxations to
which its want of solidity renders it liable. On the other hand, it
can by this situation give to the limb the motions of a whole which
compensate for those of the inferior articulations, the solidity of
which prevents the power of motion in all directions. For example,
the two articulations of which I have just spoken, are not only the
articulations of the bones that form them, of the humerus and the
femur, but also the articulations of the whole limb, which they direct
in different directions; thus the anchylosis of these articulations
renders the limb completely useless, whilst that of the inferior
articulations only destroys partial motions.

The kind of motion of this genus of articulation requires a rounded
form in the articular surfaces, whether they be concave that receive
and convex that are received. This form is in fact the only one
that can accommodate itself to extensive opposition, rotation and
circumduction united; this is the form of the superior parts of the
humerus with the scapula, and the femur with the os innominatum. The
bone which moves has a convex surface, that which serves for support a
concave one. There are in animals examples of an opposite arrangement:
that is to say that a concavity is moved in all directions upon a
convexity; but this is not found in man.

Though the two limbs have between them the greatest analogy in their
motions, yet there are some differences relative especially to their
respective uses, which in the one are for seizing and repelling bodies,
in the other destined to locomotion. The principal of these differences
is, that rotation and circumduction are found in them in an exactly
inverse ratio. The mechanical reason and advantages of this arrangement
are easily understood.

In the femur the length of the neck which is the lever of rotation,
gives much extent to this motion, which supplies the pronation and
supination that are wanting in the leg; so that every rotation of
the foot is a motion of the whole of the limb. In the humerus on the
contrary, the neck being very short and bringing the axis of the bone
near the centre of the motion, limits rotation, which is less necessary
on account of that of the fore-arm; the motion of the hand without or
within is never communicated but by a part of the limb.

As to circumduction, the length of the neck of the thigh is an obstacle
to it. In fact, let us remark that this motion is much the more easy,
when it is performed by a rectilinear lever, because then the axis of
the motion is the axis of the lever; that on the contrary, if the lever
is angular, the motion becomes so much the more difficult because the
axis of the motion is not that of the lever; and in general we can
say, that the difficulty of the motion is in the direct ratio of the
distance of the two axes.

This being settled, let us observe that the axis of the motion of
circumduction of the thigh is evidently a straight line, obliquely
directed from the head to the condyles, and distant consequently
above from the axis of the bone, the whole length of the neck. Now,
from what has just been said, it is evident, that the difficulty of
circumduction will be in the direct ratio of the length of the neck,
and consequently very great. In the humerus, on the contrary, the neck
being very short, the axis of the bone and that of the motion are
almost the same; hence the facility and extent of the circumduction. We
might fix precisely the relation of these motions by this proportion;
the circumduction of the humerus is to that of the femur, as the length
of the neck of the humerus is to the length of the neck of the femur;
which shows us how much more difficult the circumduction of the femur
is than that of the humerus. To know this, it is sufficient in fact to
know the excess of the length of the neck of the first over that of the
second.

It is easy to perceive the advantages of this very great extent in
the circumduction of the superior limbs destined to seize, and of the
limits placed by nature to that of the inferior limbs destined to
standing and locomotion. We understand also why luxations are more easy
in the first than in the second. The displacement almost always takes
place in fact, in one of the simple motions, the succession of which
forms the compound motion of circumduction, for example, in elevation
or depression, in adduction or abduction, &c. Now all these motions
being carried much further in the humerus than in the femur, the
surfaces are more easily separated.


_Second Genus._

This genus differs from the first by the absence of the motion of
rotation. Opposition and circumduction are alone met with in it. We
find examples of it in the temporal maxillary, sterno-clavicular,
radio-carpal, meta-carpo-phalangeal articulations, &c.

The want of rotation evidently supposes, from what has been said above,
the absence of an osseous head, the axis of which would make, as in the
preceding genus, an angle with the axis of the body of the bone. Thus
in all the bones of the articulations that I have just mentioned, the
articular surface is at the extremity even of the bone, and not upon
the side; the axis is the same in both cases. They form a rectilinear
lever, instead of an angular one.

The articular surfaces are in general, as in the preceding case,
uniform, without eminences and reciprocal depressions; which would
embarrass and even prevent circumduction. In the bone which serves
for support, there is a cavity more or less deep; in the bone which
is moved, there is an analogous convexity. The corresponding surfaces
of the temporal and the inferior maxillary bone, of the bones of the
metacarpus and the first phalanges, are examples of this arrangement.

This articular mode is the most favourably disposed for circumduction,
which is, as we have seen, constantly in the inverse ratio of rotation,
and which consequently has the greatest possible facility when the
lever is rectilinear, a circumstance that destroys rotation. Yet in
many articulations of this genus, circumduction is evidently less
extensive than in the humerus and the femur; but this arises from the
arrangement of the moving powers which being in much greater number
in the articulations of these two bones, compensate for the bad
arrangement of the articular surfaces for circumduction.

In the genus of articulations of which we are treating, there is
always one direction in which the motion of opposition is more easy
than in the others; for example, it is elevation and depression in
the jaw, flexion and extension in the first phalanges, in the wrist,
&c. In general there are two lateral ligaments and the capsule in the
direction in which the motions are most limited, the capsule only in
that in which they are the most extensive.


_Third Genus._

As we advance in the examination of these articular genera, the
extent of their motion diminishes. This has less opposition in many
directions than the preceding, and less circumduction which always
supposes an extensive opposition. Here this opposition is always
limited to one direction only, to that of flexion and extension, for
example.

We find this articular genus especially in the middle of the limbs, as
at the elbow, the knee, the middle of the fingers in the articulations
of the phalanges. Though the bone which composes them, inferiorly can
move by itself but in one direction, yet it borrows from the loose
motions of the superior articulation of the limb, so as to be able to
be turned in every way.

The articular surfaces are found here as in the preceding genus, at
the extremity of the bone, having the same axis as the bone; but they
differ, 1st, in this that there are many eminences and cavities fitted
to each other, an arrangement, which, by permitting the motion in one
direction, prevents it in the others. Very commonly there are two kinds
of round prominences, called condyles, which roll from before behind,
or from without within, &c. upon two analogous cavities, that are
separated by an eminence, which is received in the space between the
condyles, as we see in the femoro-tibial, phalangeal articulations, &c.
2d. The breadth of the surfaces also distinguishes this genus from the
preceding; this breadth insures its solidity, and prevents luxations,
which besides are more to be feared when they happen here where more
ligaments must be broken than elsewhere.

There is always in this genus greater extent of motion on one side,
than on the opposite. In general flexion has always more extended
limits than extension; observe in fact the condyles of the femur, of
the phalanges, &c. they are extended much further in the first than the
second direction; why? because all our principal motions are those of
flexion, and the motions of extension are as it were but to moderate
the first, and have for their object only to bring back the limb to
the position from which it can be bent again. Hence why the number,
and the strength of the fibres are much greater in the flexors than in
the extensors; why the great vascular and nervous trunks are always on
the side of flexion, as we see in the thigh, the leg, the fore-arm,
the phalanges, &c. There is always something which limits the motion
of extension, as the olecranon in the humero-cubital articulation, the
crucial ligaments in the femoro-tibial articulation.

Though in the genus which we are describing, there is no well marked
motion of circumduction, yet when the leg or the fore-arm are in
flexion, they can move laterally and even in the form of a cone, but
not in a very evident manner. In extension this is impossible, because
the lateral ligaments being much stretched, do not yield enough to
allow the bone to incline from one side to the other.


_Fourth Genus._

Every kind of opposition and circumduction is wanting in this genus,
which presents rotation alone, as we see in the articulations of
the ulna with the radius, and the atlas with the odontoid process.
Sometimes it is a concave surface rolling upon a convex one, as at the
lower end of the radius, and at the odontoid process; sometimes it is a
convex surface moving upon a concave one, as at the head of the radius;
there is always a kind of ligament which completes the concave surface,
and which thus forms a ring turning upon the bone, or in which the bone
turns.

Luxations are here very difficult, because the rotation being made upon
the axis of the bone, the ligaments are hardly more distended on one
side than the other, and are hence broken with difficulty, whatever may
be the extent of the motion. The inferior part of the radius forms a
slight exception to this rule, because it is upon the ulna, and not
exactly upon its own axis, that the bone turns in this place.

There is no rotation in the leg as in the fore-arm, because, as we have
seen, that of the thigh which is very extensive, supplies the place of
it; which the humerus could hardly do for the fore-arm, as we know when
this last is anchylosed.


_Fifth Genus._

Every kind of rotation, opposition and circumduction are wanting
in this genus, which is the most numerous, and which embraces the
articulations of the carpus, the metacarpus, the tarsus and metatarsus,
of the vertebræ between themselves by their articular processes, of
the atlas with the occiput, of the humeral extremity of the clavicle,
the sternal of the ribs, and the superior of the fibula. There is only
a kind of slipping more or less obscure, and in which the osseous
surfaces hardly ever leave each other. These surfaces are almost
all plain, very close together, united by a considerable number of
ligaments, and so strong in their connexion, that luxations hardly ever
happen to them. Another reason moreover which renders them difficult,
is that all this genus of articulations belongs almost wholly to short
bones; now we know, that the motion imparted to a bone has a power
of action which is in direct ratio of its length, and in the inverse
of its smallness; for example, the same power applied to the tibial
extremity of the femur, would luxate much more easily the ischiatic
extremity, than if it acted upon the middle of this bone.

As the separate motion of each of the articulations of the fifth genus
is almost nothing, nature usually unites several at the same place, for
the purpose of producing a sensible, general motion, as we see in the
carpus, the tarsus, the vertebræ, &c.; this is also a reason of the
difficulty there is in luxating this genus of articulations. In fact,
how great the general motions may be, two bones, taken separately,
move but little upon each other; now it is only the extent of the
motion of the two separate bones from each other, that can produce the
displacement.


III. _Observations upon the Immoveable Articulations._

We have only pointed out orders in this class, because its varieties
are not sufficiently great to assign genera for them.

1st. The order of immoveable articulations with surfaces in
juxta-position, is met with where the mechanism of the part alone
is almost sufficient to insure the solidity of the bones which are
found only placed at the side of each other, without holding by any
insertion, and having only between them a slight cartilaginous layer;
the superior maxillary bones, wedged in between the malar bones, the
ossa ungues, the ethmoid, the ossa palati, the vomer, and the frontal
bone, are supported more by the general mechanism of the face, than
by any articular attachments that unite them to each other; thus the
squamous portion of the temporal bone supports the parietal, more
by the abutting arches, than by the manner of the union of their
respective surfaces. Remove this general mechanism of the part, you
will soon see all the articulations separate.

2d. The order of immoveable articulations with inserted surfaces,
owes also in some measure its solidity to the general mechanism of
the part; but this mechanism would be insufficient to insure this
solidity; thus the bones, instead of having almost plain surfaces,
exhibit very evident prominences and depressions which are inserted
into each other, as we see in the articulations of the parietal bones
with each other, with the sphenoid, the occipital, the frontal, &c.;
these are called sutures. This order sometimes approximates the
preceding, as in the union of the parietal and frontal bones, which,
reciprocally aiding each other, are supported by this mechanism,
more than by their insertions; sometimes it resembles the following
order, as in the articulation of the occipital and parietal bones, in
which the very deep insertions almost alone insure the solidity of
the union. This order is never seen except upon the edges of the flat
bones; the insertion of these edges compensates for their want of size,
by multiplying the points of contact. The eminences and depressions
forming the insertion are always of an irregular form and size. They
are exactly fitted to each other, they are not alike in two bones of
the same species, taken from two different subjects; so that we cannot
unite to a detached left parietal bone, the right parietal bone of
another individual. There has been much dispute upon the formation
of the sutures; they are an effect of the laws of ossification, an
effect which we can account for no more than we can for all the others,
and all the general phenomena of growth; we shall see the progress
they follow in this formation. This articular order is gradually
effaced with age, and the bones unite together by the ossification of
the thin intermediate cartilage. It is more rare that the preceding
order disappears. I have seen, however, in extreme old age, different
articulations of this order cease to be evident, those of the maxillary
bones between themselves especially.

3d. The order of articulations with implanted surfaces borrows none of
its solidity from the mechanism of the part; it owes it entirely to
the relation of the surfaces, which are so united and embraced by each
other, that displacement is impossible. There is but one example of
this articular order, it is the teeth with the jaws.

Age does not here efface the articulation, and thus confound the two
bones as in the preceding orders, because the medium of union is the
palatine membrane, which belongs to the mucous system, and which by its
organization has no tendency to ossification; whereas in the preceding
cases, the intermediate cartilage has a natural disposition to become
encrusted with the phosphate of lime.


IV. _Of the Means of Union between the Articular Surfaces._

The articular surfaces would soon separate, if different organs did not
retain them in place. These organs are the cartilages and the membranes
for the immoveable articulations, the ligaments and the muscles for the
moveable.


_Union of the Immoveable Articulations._

The two first orders of immoveable articulations, those with inserted
surfaces and those with surfaces in juxta-position, have cartilages
between the osseous surfaces, the breadth and thickness of which
are found so much the greater in proportion as they are examined in
subjects nearest infancy. Almost all the bones of the head are held
together in this manner, which allows them to yield a little, and
consequently prevents their fracture.

In the articulations of the pelvis, there are besides the cartilages,
ligaments; but as these articulations perform in certain cases small
sliding motions, we can consider them as intermediate between the
moveable and immoveable articulations; it is on this account that they
have the two kinds of organs especially destined to strengthen the
articular surfaces of each of the classes, viz. the cartilages and the
ligaments.

The immoveable articulations with implanted surfaces, an order which
comprehends only the teeth, have nothing between the surfaces as a
means of union, but a mucous membrane, the palatine. Hence why in the
swellings of this membrane, in scorbutic affections, after the use of
mercury, &c. the teeth become loose.


_Union of the Moveable Articulations._

The moveable articulations with contiguous surfaces have the ligaments
especially as a means of union, which are found in the five genera,
but under different forms which will be examined hereafter. This
kind of organ unites much suppleness with great resistance, a double
attribute which it derives from its peculiar texture, and which renders
it very proper for this function. Let us observe however that these
two properties are in an inverse ratio in the two extreme ages of
life, that suppleness is the companion of infancy, that stiffness and
resistance are the character of the ligaments in old age. Hence in
part the multiplicity of motions in one age, and their slowness and
difficulty in the other.

The cartilages are not in this articular order, as in the preceding,
means of union, but means of motion, by their smooth and polished
surfaces.

As to the synovial membrane that is found exclusively in this order,
such is its extreme tenuity, that it can hardly be considered as
uniting the surfaces, and its use appears to be confined to the
exhalation of synovia.

It is not the same with the muscles; they can be considered as forming
at the same time around the moveable articulations, a power for the
whole of the bone, and a resistance for its extremities, which they
prevent from being displaced, by forming around them supports, the
efficiency of which is in proportion to the efforts that are made to
displace these extremities. In fact, it is in the great motions that
these efforts are the most considerable; now then the neighbouring
muscles of articulation strongly contracted, hard during their
contractions, have a powerful tendency to prevent the osseous extremity
from abandoning that which corresponds with it. In rest when the
relaxed muscles offer but little resistance, the effort for support
is nothing. A paralyzed limb can be luxated much more easily than
another, by external violence.

The order of moveable articulations with contiguous surfaces, has as a
means of union, a substance, the nature of which is between that of the
ligaments and that of the cartilages.


ARTICLE FIFTH.

DEVELOPMENT OF THE OSSEOUS SYSTEM.

There is no system in which anatomists have traced in a more accurate
manner than in this, the different states in the different periods of
life. The remarkable difference of a bone examined in the first months
when gelatine almost alone composes it, compared with a bone of an
adult in which the calcareous substance predominates, has especially
arrested their attention upon this point. Let us examine the phenomena
of ossification in all the ages; these phenomena should be considered
during and after growth. In general, while this continues, there are
some portions of the osseous system not ossified, as the neck of the
femur, for example; ossification is not complete, the bones are not
perfectly developed until towards the sixteenth or eighteenth year, and
sometimes even later.


I. _State of the Osseous System during Growth._

We commonly distinguish three states in the development of the bones,
viz. the mucous, the cartilaginous and the osseous states.


_Mucous State._

The mucous state may be considered as existing at two periods: 1st. In
the first days of the development of the embryo, a period in which
the whole of its organs forms only a homogeneous and mucous mass, in
which it is not possible to distinguish any line of demarcation, and in
which the parenchymas of nutrition alone exist. All the organs are then
of the same nature; the bones are in fact mucous like all the other
organs, if by this word we understand a state in which the cellular
texture existing alone with the vessels and the nerves, is penetrated
by so large a quantity of juices, that it has the form of a mucilage,
and gives the appearance of it to the embryo. 2d. We may understand by
the words mucous state, that more advanced period of osseous nutrition,
in which the bones can be already distinguished, seen through the
transparency that the other parts of the limb still have, and in which
they have a consistence much greater than that of the parts which
surround them; now this state is only the commencement of that of
cartilage; for the parenchyma of nutrition takes the cartilaginous
character when it begins to be penetrated by gelatine, and it is in
fact penetrated by this substance when it has more consistence, since
it is that which gives it this consistence, and hence an existence
distinct from the surrounding parts. If in the early periods, this
cartilage is softer, if it flattens under the finger when pressed, if
it even has an appearance partly mucous, it is because the gelatine is
not yet in sufficiently large proportion, and because the nutritive
parenchyma still predominates; gradually its quantity increases, and
then the cartilaginous nature is more evidently developed.

It follows hence that the bones have three periods in their
development; one is common to them with all the other organs; it is the
mucous period; the two others especially characterize them; these are
the cartilaginous and osseous periods. Let us examine their phenomena.


_Cartilaginous State._

All the bones are cartilaginous before taking their last form.
This state of cartilage begins at a period that is difficult to be
determined; it is when on the one hand the circulating system begins to
carry gelatine and present it to the organs, and when on the other the
organic sensibility of the parenchyma of nutrition of the bones is put
in relation with this substance. Then the consistence of the bone is
constantly increasing, because the gelatine is constantly accumulating;
now it accumulates in the same direction that the phosphate of lime
afterwards takes; that is to say, in the long bones it is in the
middle of the body, in the flat bones it is in the centre, and in the
short ones it is in the centre also, that this substance is at first
exhaled, which afterwards extends gradually to the extremities of the
first, the circumference of the second and the surface of the third.
I would observe however that we do not see, during the formation of
the cartilaginous bone, those longitudinal striæ in the long bones,
radiated ones in the flat, irregularly crossed ones in the short, which
distinguish the osseous state in its formation, and which seem to
indicate to the eye the course of the phosphate of lime.

The cartilaginous state exhibits a peculiarity that distinguishes
it from the osseous state; it is that all the bones that are to be
afterwards united by means of cartilage, such as those of the cranium,
the face, the vertebral column and the pelvis make only one piece;
whilst all those that are to be held together by ligaments, whose
articulations are consequently moveable, are found very distinct, as
the femur, the tibia, the clavicle, &c.

The broad bones, those of the cranium especially, do not exhibit in
so distinct a manner the cartilaginous state. Their appearance, at
this period of ossification, is even rather membranous. It arises from
this; as they are found interposed between the periosteum and the
dura mater, and as their tenuity is very great, we can with difficulty
distinguish them on the interior of these two membranes. But when we
dissect the parts with care, we can distinguish the bone yet soft, from
this double covering.

The cartilaginous state appears in the clavicle, the scapula, the
ribs, before being discoverable in the other bones in which it is
afterwards seen. When we examine the bones in this state, we find them
of different consistence and solidity; where the exhalation of gelatine
has commenced, they are incompletely cartilaginous; as we go from this
point, they partake more or less of the mucous state. The cartilaginous
bone has no internal cavity, no medullary system, &c.


_Osseous State._

When the whole bone is cartilaginous, and even when some points appear
to be still mucous, the exhalation of calcareous substance begins, and
then the osseous state manifests itself; the following is the manner;
the bone becomes more dense, then of a deeper colour, and finally
of a very evident yellow in its middle, that is to say where the
ossification should begin; gradually a red point appears; these are the
vessels that begin to receive the red portion of the blood, and not to
be developed as some anatomists pretend, to be hollowed out according
to their expression, by the force of the impulse of the heart. They
always existed; the white fluids alone penetrated them before, then the
red globules are admitted into them. At the same time the neighbouring
parts are encrusted with calcareous substance. This period is then
remarkable in two particulars, viz. in respect to the entrance of the
blood into the cartilaginous bone, and in regard to the exhalation of
the phosphate of lime. These two phenomena are always inseparable; when
there is redness in one part of the cartilages, there are also osseous
points; this is observed not only in common ossification, but also in
those which are not so, such as the ossifications of the cartilages
of the larynx, of the ribs, &c. When we examine the progress of the
exhalation of the earthy substance, we see always in the bones, whether
long, flat or short, a very red vascular layer, between the cartilage
and the portion of ossified bone. This layer seems to serve as a
precursor to the osseous state. Why do the vessels of the bones which
before had admitted only white fluids, receive then red globules? It
is not, as Boerhaave would have said, had he treated of ossification,
because their caliber increases, but because the sum of their organic
sensibility increasing, they are then found in relation with the red
portion, which until then was foreign to them. Their caliber might be
treble or quadruple the diameter of the red globules, but these would
not enter if the organic sensibility repelled them, as the larynx
rises against a body which attempts to enter it, though this body may
be infinitely less than the glottis. It is by an increase of organic
sensibility, that must also be explained how the bone, until then a
stranger to calcareous substance, being in relation only with the
gelatine, appropriates also to itself the first of these substances,
and is penetrated with ease.

I will observe only that there is this difference between the
exhalation of the two, that the first comes immediately from the red
portion of the blood, since wherever it is deposited, there is, as I
have said, blood vessels; whilst the second appears to come immediately
from the white fluids, since the vessels of the tendons, the cartilages
and the other parts that they nourish, do not evidently receive in
their natural state any red globules, and all that circulates in them
appears to be white.

The osseous state commences with the end of the first month in the
clavicle, the ribs, &c.; it is a little more slow in the other bones;
we know not its precise period. The following is its progress in the
three kinds of bones.


_Progress of the Osseous State in the Long Bones._

We distinguish at first in the middle of these bones, a small
osseous cylinder, very slender in its centre, enlarging towards the
extremities, hollow in the interior for the rudiments of the medullary
system, perforated by a nourishing foramen whose size is then in
proportion very great, receiving also a very large vessel. This osseous
cylinder, at first very slender in comparison with the cartilaginous
extremities of the bone, is in a very evident disproportion to them in
this respect; it is formed of very delicate fibres, and is gradually
enlarged and extended, until it reaches near the extremities where
it is found at birth; the most of these extremities are not then
bony. Some time after, and at a period which varies in the different
bones, there is developed in these extremities an osseous point which
begins at the centre, and which is always preceded by the passage of
the blood in the vessels. These new germs increase at the expense of
the cartilage which is gradually lessened between the body and the
extremity of the bone; at the end of some time there remains only a
slight partition which ossification also seizes upon; so that the bone
is then wholly osseous from one extremity to the other. The secondary
points which are developed in the different apophyses, also unite; so
that its substance is everywhere homogeneous. It is not until the age
of sixteen or eighteen years, that nature has completely finished this
work.


_Progress of the Osseous State in the Broad Bones._

The mode of origin of ossification varies in this kind of bones. Those
which are symmetrical, have always two points or more, which correspond
upon each side of the median line; sometimes one of them is found upon
this line. When these points of ossification are in equal number, they
are always upon the sides; if they are in unequal number, one of them
is upon the line.

The irregular bones sometimes have but one of them, as in the parietal;
at other times many appear in them, as in the temporal; but there is
never a similar arrangement among them; only they correspond with those
of the opposite bone.

At the first point of ossification in a broad bone, we perceive at
first reddish spots, then we observe the phosphate of lime spreading in
rays from the centre to the circumference of the bone. The osseous rays
are very evident upon the bones of the cranium. Portions not ossified
at first fill their interstices, which new rays afterwards occupy. All
terminate in an unequal manner, without touching, so that by separating
an ossified portion of a broad bone from the membranous portion to
which it belongs, its circumference looks cut like the extremity of a
comb; hence, as we shall see, the origin of sutures.

The delicacy of these bones is extreme in the early periods; they have
not then any of the texture of the cells. At birth but few of the
osseous centres are yet united; cartilaginous and membranous spaces
separate them; these spaces are greater towards the angles than towards
the edges, and generally at points the most distant from the primitive
osseous centres. The bones with many points of ossification are formed
of separate pieces, more or less distant from each other. Those with
one point only, have but one piece.

After birth these bones extend more and more, their thickness and
hardness increase; they are divided into two compact layers, the space
between which is filled by the texture of the cells; gradually they
touch at their edges, and then the sutures are formed in the cranium;
for there is this difference between their ossification and that of
the long bones, that it takes place always from the centre to the
circumference, and that new osseous points are not developed at the
circumference to meet those of the centre. But when this happens, the
union does not then take place as in the long bones, but sutures are
formed; and it is this which occasions the ossa wormiana, which are so
much the larger as the osseous point is the sooner developed, because
it has had time to extend itself more, before meeting the general
ossification of the bone.

When a broad bone is developed by many points and there exists upon its
surface an articular surface, it is usually the centre in which all the
points unite at the period in which ossification terminates; we see
this in the cotyloid cavity, in the condyle of the occipital bone, &c.

There is often in the broad bones two well marked periods for their
ossification; it is so in those which, like the sacrum and sternum, are
developed by a great number of points. These points begin at first to
unite into three or four principal pieces which divide the bone; this
is the first period; then much later, the union of the pieces takes
place; this is the second period.


_Progress of the Osseous State in the Short Bones._

The short bones remain in general longer cartilaginous than the others.
Often at birth many are still so, those of the tarsus and carpus in
particular. The body of the vertebræ is ossified sooner; a point is
developed at the centre, and extends over the whole surface.

These phenomena are nearly analogous to those of the ossification of
the extremities of the long bones, which the short bones resemble so
much. After birth, the whole cartilaginous portion, is, if we may so
say, invaded by the calcareous substance, which mixes with it, and
there is finally only the articular cartilages left.

There are bones, as the occipital and sphenoid, which partake of the
character of the broad and short bones; their ossification is mixed,
and follows the mode of one or the other, according to the part of the
bone that we examine.


II. _State of the Osseous System after its Growth._

The bones, having become completely ossified, continue to undergo
different phenomena which anatomists have too much neglected. The
general growth in height is terminated when ossification is complete;
and it even appears that the term of these two is nearly the same; but
that in breadth continues for a long time after; compare the small and
slender body of a young man of eighteen years, with the stout and well
proportioned one of a man of forty, and you will see the difference.
The bones follow the general law; their nutrition is prolonged for
their thickness, when that for their length ceases. It appears that
then the vessels which penetrate by the foramina of the first and
second order, do not contribute to this nutrition, which draws its
materials from those of the third; now, as we know that these very
superficial vessels are arrested in the external fibres of the bone,
and do not penetrate within, we understand, 1st, how, the growth going
on without, the bone increases in thickness; 2d, how this increase
takes place especially on the compact texture, the proportional
thickness of which is in the direct ratio of the age, as we may see
by inspecting the different bones of the child, the adult and the old
person.

This external growth has made it believed that the periosteum
contributes to it especially by the ossification of its layers; but we
shall see in the article upon this membrane, what opinion should be
entertained upon this subject.

It is principally at this period in which the work of nutrition seems
spread upon the osseous surface, that the different eminences, which
are scattered over this surface, become more evident; then especially
all the prominences of insertion become more prominent; there is
in respect to these eminences a remarkable difference between the
skeleton of a child and that of a full grown man. In the fœtus they
hardly exist, as we see particularly by the different apophyses of the
vertebræ, the spinous especially. As these eminences are generally the
most distant parts from the primitive osseous centres, it appears that
it is to this circumstance that must be attributed the slowness of
their formation, since ossification always goes from points where it
begins, to the most distant ones.

When the bone has all its dimensions it still continues to be the
seat of a very active nutrition; exhalation constantly brings to it
gelatinous and calcareous substances which absorption afterwards takes
up; so that it is continually composed and recomposed. The experiment
with madder evidently proves this; if we feed an animal for some time
upon this, the bones become red much more easily, in proportion as
the animal is younger; so that by amputating a limb after some time,
the bones have an appearance wholly different from what is natural
to them; if, after this amputation, we discontinue the use of the
madder for some time, and then amputate another limb, the bones will
be found to have entirely resumed their natural colour; now we know
that the calcareous substance is the vehicle of the colouring matter,
since while the bones are only cartilaginous the madder has no effect
upon them. The calcareous substance is then alternately furnished and
taken away from the bones. Besides, the formation and resolution of
exostoses, the softening and brittleness of the bones, the phenomena
of the production of callus, &c. are they not an evident proof of
the exhalation and absorption of this principle? It appears clearly
that the urinary system is the way by which nature gets rid of the
calcareous and even of the gelatinous substance. It would be curious
to analyze accurately the urine of ricketty patients, and that of
those affected with cancer; it is probable that the first of these
substances predominates in the urine of the first, and the second in
that of the others; I know of no positive experiments upon the subject.

Can we, by giving to patients gelatine or the phosphate of lime,
restore to their bones the suppleness or solidity which they have lost?
No, because it is necessary not only to introduce these substances into
the economy but also to restore to the bones their peculiar organic
sensibility which they no longer have, and which, by placing these
substances in relation to them, would enable them to appropriate these
to their own nourishment. The blood might be loaded with earthy and
gelatinous principles, and the bones would repel these principles, so
long as their sensibility was not in relation with them.

The double motion of nutrition continues always in the bones, as we
advance in age; but its proportions change. The gelatine is constantly
diminishing and the calcareous substance constantly increasing.
Finally, in extreme old age this last predominates so much, that it
would destroy their life, if general death did not take place before
that of the bones.

It is to this that must be attributed the greyish colour that these
organs then take; hence also their constantly increasing weight; hence
consequently the difficulty of the motions of the limbs, since at the
same time that the force of the muscular powers is diminished by age,
the osseous resistance which they have to overcome increases.

At this period of life, the calcareous substance predominates so
much in the economy, that it is thrown upon different organs, such
as the arteries, the cartilages, the tendons, which then take the
osseous character. We might say that by accumulating in our parts this
substance foreign to life, nature wishes to prepare them insensibly for
death.

In general, it is those organs whose nutritive substance is gelatine,
which have the greatest tendency to be placed in relation with the
calcareous substance, and consequently to be encrusted with it. Hence
why the cartilages especially are ossified; why those of the sutures
disappearing, the bones of the cranium become continuous; why the
larynx is finally almost all osseous; why the cartilages of the ribs
are often as solid as the ribs themselves; why oftentimes many vertebræ
united form a more or less considerable continuous mass. I would
observe however that the arteries, which have so great a tendency to
ossification, are not so evidently gelatinous as many other substances
which ossify much less easily, as the tendons for example.


III. _Peculiar Phenomena of the Development of the Callus._

Nothing is easier after what has been said upon the osseous nutrition,
than to understand the formation of the callus. We know that it has
three periods, 1st, the development of the fleshy granulations; 2d,
their change into cartilage; 3d, the change of this cartilage into
bone. This triple phenomenon takes place in a space of time that varies
according to the age, the fracture, the kind of bone, &c. but which is
in general longer than that of the other cicatrices.

The development of fleshy granulations is a phenomenon common to
every species of organ which has experienced a solution of continuity
and whose divided edges are not in immediate contact. Here these
granulations arise from every part of the divided surface, from the
periosteum, the compact texture and that of the cells, the last
especially. Those of one side unite to those of the opposite. Thus far
the osseous cicatrix does not differ from that of the other parts. This
state corresponds with the mucous state of natural ossification. As the
fleshy fibres are but the extension of the nutritive parenchyma, they
have its vital forces; their organic sensibility follows the same laws
as in ordinary nutrition; at first it is in relation with gelatine;
this is then exhaled; then commences the cartilaginous state; then the
osseous cicatrix takes a peculiar character, which distinguishes it
from that of the other organs.

At the end of a longer time, the organic sensibility increases in the
parenchyma of cicatrization which the fleshy granulations form; then
these become in relation with the calcareous substance which comes to
the bone, and which they had until then repelled; they admit it then,
as well as the red portion of the blood which always precedes it in
every species of ossification.

Hence we see that the callus is cellular and vascular in the first
period; that in the second it contains cellular texture and vessels,
with gelatine; that in the third, it has cellular texture, vessels, and
gelatine, with calcareous substance.

It has not the regular forms of the sound bone, because the parenchyma
of cicatrization arising irregularly upon the osseous surfaces, the
exhalation and absorption of gelatine cannot be made in a precise and
regular manner. The callus is so much the larger in proportion to the
separation of the ends of the bone, because the fleshy granulations
having had more space to go over in order to meet, are more extensive,
and consequently have absorbed more nutritive substance.

If the constant motion of the fractured ends prevents on each side
the granulations, or what is the same thing, the two parenchymas of
cicatrization from uniting, then, notwithstanding the exhalation of
the nutritive substances in each of them, the bone does not unite, and
hence the preternatural articulations.

Callus is formed with difficulty when the ends divided and laid
bare, suppurate with the neighbouring parts, as happens in compound
fractures, because the formation of pus expends the nutritive
substances destined to repair the fracture. The further considerations
upon this singular production belong to pathology.

I have not exposed in this chapter the ideas of the ancients, who
thought that the bones were formed by the hardening of an osseous
juice, the existence of which there is nothing to demonstrate; nor
those of Haller, who imagined that the heart hollowed out arterial
channels in the osseous substance by its own impulse, and hardened this
substance by the pulsation of the arteries; nor those of Duhamel, who
made every thing depend upon the periosteum; I refer to various works
that have a thousand times refuted these opinions.

Without refuting any one in particular, I would remark that they have
one fundamental error, viz. that of considering osseous nutrition in
an insulated manner, of not presenting it as a division of general
nutrition, of admitting for its explanation reasonings only applicable
to the bones, and which are not derived as consequences from those
which serve to establish the nutrition of all the organs. Let us
never lose sight of this essential principle, upon which rest all the
phenomena of the economy, viz. that over a multitude of effects, a very
small number of causes only presides. Let us mistrust every explanation
which is partial and mutilated, which circumscribes the resources of
nature according to the limits of our weak understandings.


IV. _Peculiar Phenomena of the Development of the Teeth._

The teeth, differing in part by their texture, from the other bones,
have also a peculiar mode of nutrition which we shall now examine. But
as the knowledge of this supposes that of the general structure of the
teeth, it is proper to explain here that structure, referring their
description to the examination of the bones of the face.


_Organization of the Teeth._

The teeth are formed by two substances, one external, of a peculiar
nature, called enamel, the other internal, which is the common base of
it, and the texture of which is the same as that of the other bones.
They have besides a cavity which contains a spongy substance, as yet
but little known.


_Hard Portion of the Teeth._

The enamel of the tooth is only seen around the crown; some anatomists
have thought that it extended a little upon the root, an opinion
founded no doubt upon the extreme whiteness that the root often has in
detached teeth, and which makes it impossible to distinguish the line
of demarcation. But a very simple experiment proves this demarcation;
it consists in macerating the tooth in diluted nitric acid. The acid
immediately attacks both the root and the crown which it softens; but
the first becomes yellow like almost all animal substances exposed to
its action, whilst the other preserves its colour, and even becomes
whiter. This experiment also proves that their respective natures are
essentially different.

The enamel, thick on the top of the crown, grows thinner towards the
root, an arrangement required by its use, which is to defend the tooth,
to support principally the efforts of mastication, which are made
especially upon the top of the crown.

This substance hard, compact, particularly when it has remained a long
time in the air, acted upon with difficulty by the file, is composed
of very close fibres, the direction of which cannot be traced. The
medullary oil does not appear to penetrate it; it does not burn, but
breaks by the action of fire, and is thus separated from the other
substance, which, exposed to heat, at first becomes black, then burns
like the other bones and gives out the same odour.

Is the enamel organized, or is it only a fluid which, oozing at
first from the external surface of the tooth, afterwards becomes
there hardened and concrete? This question is not I think easy to
be resolved. The enamel has in fact attributes which seem equally
favourable to both these opinions. On the one hand it is sensible,
like every thing that is organized; it gives us, much more evidently
than the hair or the nails, the sensation of bodies which strike it.
The diluted acids, the vegetable especially, raise its sensibility so
much, that the least touch becomes very painful a long time after their
use. The teeth are then, as we call it, on edge. On the other hand the
enamel has many characters that seem to denote a want of organization.
1st. It never inflames, or becomes the seat of any tumour, or any
alteration which softens its texture; it never experiences any
alteration, which by raising its life, renders it more sensible than in
a natural state, as happens to the hair, for example, which ordinarily
insensible, has a very great vital activity in the plica polonica. In
fact we often judge of the vitality of organs more by their morbid
alterations, than by their natural state. 2d. It appears that there
does not take place in the enamel alternate exhalation and absorption
of nutritive matters, or at least if it does, it is not sensible.
Rubbing wears away this substance, which is never replaced; this is
remarkable in old people, and in those who are in the habit of often
striking their teeth together. We know that we file the enamel like an
inorganic body, and that it is not reproduced, whilst the hair and the
nails evidently grow after being cut. File the extremity of a long bone
after amputation; fleshy granulations will soon grow upon the filed
surface; the action of the instrument will be a stimulus which will
develop the vital phenomena.

The osseous portion of the tooth composes the whole of the root and the
interior of the crown; it is formed by the compact texture, very dense,
having great resemblance to that of stone. It has none of the texture
of the cells. Its fibres, very close to each other, have various
directions, very difficult to trace, but which in general follow
that of the roots; it is necessary, in order to see this direction
perfectly, to soften the teeth in an acid.

Each tooth has a cavity situated in the crown, of the same form as the
crown, diminishing in diameter as we advance in age, communicating
externally by small canals, the number of which is equal to that of the
distinct roots of the tooth, and which open at the end of these roots.
This cavity is lined by a very delicate membrane on which the vessels
ramify, and which, with its opposite face, covers the marrow.


_Soft Portion of the Tooth._

This is a spongy substance which appears to be formed by the
interlacing of the vessels and nerves belonging to each tooth, but
the nature of which is not yet well understood; we know only that it
has a very great animal sensibility equal to that of the medullary
organ. This is proved, 1st, by the pains of carious teeth in which the
marrow is bare, and which are, as we know, extremely acute; 2d, by the
introduction of a probe into the opening occasioned by caries, this
produces no pain until it comes to the marrow, and then it is extreme;
3d, by opening a socket of a very young animal that has not yet cut its
teeth. At this age the marrow is very considerable and the tooth being
small in proportion, it is easy to raise the tooth without injuring it,
because it has as yet no root and the opening at the base of the crown
is very large. The tooth being raised and the marrow thus laid bare,
if it is irritated in any way the animal gives signs of the most acute
pain. I have often made this experiment, always easily done, on account
of the want of thickness of the osseous layers which then form the
sockets.

The teeth have remarkable sympathies, which extend not only to the
solid part, but also to the marrow. As this is much greater in
proportion in the early ages, as it is almost the predominant part
of the tooth, these sympathies are then more numerous and evident.
In these sympathies, sometimes the animal and sometimes the organic
properties are brought into action.

The sympathies of animal sensibility are evident in those pains of
which the teeth become the seat from the action of cold or moisture
upon the cutaneous system; in those produced in the face and the
head by the caries of a tooth. Fauchart relates a case of obstinate
hemicrania, which was immediately removed by the extraction of a tooth.
The sensibility of the ear and the eyes is changed in some violent
cases of tooth ache. The animal contractility is also brought into
action in the sympathies of the teeth; nothing is more frequent in
dentition, than convulsions of the voluntary muscles. Tissot speaks of
a spasm of the muscles of the jaw, which was cured by the extraction of
two carious teeth, and of a convulsion in the muscles of the neck that
occasioned death, the primitive source of which was in a decayed tooth.

The organic sympathies are not less often produced by affections of the
teeth. Spasmodic vomiting, diarrhœa, frequency of the pulse, oftentimes
involuntary evacuation of urine, phenomena, over which the sensible
organic contractility of the stomach, the intestines, the bladder and
the heart presides, are the frequent effects of dentition and violent
pains of the teeth, especially of the first. The insensible organic
contractility, and the organic sensibility are brought sympathetically
into action in the enlargements of the parotid gland, in the general
swelling of the face, in the increased secretion of saliva and
sometimes in the erysipelatous inflammations which take place from an
acute affection of the teeth.

The sympathies of the teeth often take place between the two
corresponding teeth of the same row or of the two rows. My first upper
molar tooth of the left side is a little carious; from time to time it
gives me pain, then invariably the first molar tooth of the right side
becomes as painful, though it is sound. There are other cases in which
a tooth being painful below, sympathetic pains are felt in that which
is above, and vice versa.

The structure of the teeth having been explained, let us see how their
different substances are developed. This subject of osseous nutrition
does not appear to me to have been clearly illustrated by any author.
I shall attempt to explain it better. There are two dentitions, one
is provisional and limited to the first age, the other belongs to the
whole life; each should be considered before, during, and after the
cutting of the teeth.


_First Dentition considered before Cutting._

The phenomena of dentition before the period of cutting are these; the
jaws of the fœtus are closed the whole length of their upper edge; they
appear to be homogeneous at first view; but examined in their interior,
they exhibit a row of small membranous follicles, separated by delicate
partitions, disposed like the teeth of which they are to serve as the
germ, and having the following arrangement.

The membrane which serves as a covering to the follicle forms a sac
without an opening, which lines at first all the parietes of the
socket, to which it is attached by elongations. At the place where the
vessels and nerves enter, this sac leaves the socket, becomes detached,
is folded into the form of a canal which accompanies the vascular and
nervous bundle, and afterwards spreads out upon the marrow of the tooth
which is the termination of the bundle.

It follows from this that this membrane has the general conformation of
the serous membranes, in the shape of some kinds of night-caps. It has
two portions, the one attached and lining the socket, the other loose
and covering the marrow, as for example, the pleura has a costal and a
pulmonary portion. The marrow and the vessels, though contained in its
duplicature, are in truth found without the cavity, which is lubricated
by a simple exhalation. I have found that this exhalation was like
that of the serous membranes, essentially of an albuminous nature; the
action of the nitric acid, that of alkohol and of fire incontestably
prove it. Subjected to the action of one of these agents, especially
the first, the membrane whitens immediately. The layer of albumen which
covers it becomes concrete and coagulated, as when we make a similar
experiment upon a serous surface.

The marrow, very considerable at this period, is found suspended, like
a bunch of grapes, from the extremity of the vessels and the nerves.

It is upon the medullary portion of the membrane of the follicle, and
upon the surface of its loose extremity, that the first osseous point
is developed; it soon extends, and takes precisely the form of the top
of the crown, which it is afterwards to form, that is to say, that it
is quadrilateral in the molar teeth, pointed in the canine, and wedge
shaped in the incisors. Developed at first nearest the gums, it extends
afterwards along the vascular and nervous stem, it is moulded upon it
as it approaches the part of the alveolus where it enters; so that
it exhibits on this side a concave surface which embraces the pulpy
portion of the membrane, and adheres by several vascular elongations;
and as this portion is loose, the first rudiment of the tooth floats
also in the cavity of the membrane, as we can see very well by cutting
the alveolar portion of this membrane, after having destroyed the
corresponding part of the alveolus.

The following consequences result from this kind of development; 1st.
The crown is first formed, and the root is not produced but as the
ossification in length advances upon the portion of membrane lining the
vascular and nervous bundle. 2d. As all the vessels that come to the
tooth enter at its internal surface, and as the external is entirely
free in the cavity of the membrane, the ossification in thickness
is made especially at the expense of the internal cavity which is
constantly contracting, as well as the marrow, an arrangement, the
reverse of that of the other bones, the ossification of which commences
at a point placed in the centre of the cartilage, and which at first
solid in the middle, afterwards become hollow for the medullary
cavities and those of the cells, which are always enlarging. 3d. After
the ossification of the tooth, the portion of the membrane of the
follicle which lined the alveolus, remains the same, whilst that its
portion corresponding with the marrow, originally free at the other
side, becomes adherent on this side to the whole dental cavity which it
lines, of which it forms the membrane noticed above in the article on
the structure of the teeth, and which is thus found between the marrow
and the osseous substance. 4th. The marrow of the tooth is the part
first formed, and the most considerable in the first periods of life.
It appears that the osseous substance is next formed, and that the
enamel afterwards arises on the exterior of this. I have not yet been
able to make evident the manner of its origin.

It is difficult to ascertain at what period the membraneous follicle is
formed; that of the first ossification appears to be from the fourth
to the fifth month. At the time of birth, we find the twenty teeth of
the first dentition already advanced; the whole crown is formed; the
beginning of the root appears also in the form of a broad tube, with
extremely delicate parietes, and which is constantly becoming longer
and thicker; when it reaches the bottom of the socket, the tooth
immediately appears externally as this is too narrow to contain it.

The number of teeth, less in the first than in the second dentition,
gives a peculiar form to the jaws of the fœtus and the infant,
especially to the lower one, which is less elongated in front, and
consequently wider in proportion than in the adult, in whom in order
to receive all the teeth, the alveolar border must necessarily be more
extended. This arrangement of the lower jaw has a great influence in
the expression of the physiognomy.


_First Dentition considered at the period of Cutting._

The following phenomena take place about the sixth or seventh month
after birth, very rarely sooner, still more rarely before birth, though
there are examples of this, as is proved by the history of Louis XIV.
At first the two small incisor teeth of the lower jaw appear, sometimes
together, sometimes separately; soon after the corresponding incisors
of the superior jaw. A month or two later, the four other incisors
are cut. At the end of the first year, the four canine teeth usually
appear. At the end of the second, or often later, two molar are cut
in each jaw and two others soon follow. Each cutting almost always
begins in the lower jaw. At the age of four years, four and a half,
sometimes five or six, always at a very uncertain period, there appear
below two other molars and then two above, which complete the number
of twenty-four teeth forming the first dentition; all these except the
last four fall out and are replaced by new ones.

The following is the mechanism of this first dentition; the
ossification extending constantly towards the root, the tooth can no
longer be contained in the socket; it pierces the alveolar portion of
the membrane and the mucous membrane of the mouth and an intermediate
medullary texture that separates them, with much ease, as this triple
layer gradually becomes thinner as the cutting approaches. Is this
phenomenon owing only to the mechanical pressure of the tooth? I think
that there is another cause; for observe that here the membranes are
very little raised before rupturing; whilst that in polypi and other
tumours that sometimes arise under the membrane of the gums, it is
infinitely more stretched, still it does not break, but is only lifted
up. The mechanism of the opening of the gums is not more known than the
principle of the severe accidents which are sometimes connected with
it. The sac which formed the original membrane of the follicle being
thus open, its portion which lines the socket unites to the membrane
of the mouth, becomes continuous with it and at the same time adheres
intimately to the neck of the tooth; and as during the development
of the root, the internal face of this membranous portion, at first
loose as we have seen, has gradually contracted adhesions with it, it
follows that this root is found fastened between the alveolar portion
which lines its exterior, and the medullary portion which covers the
interior; it is this which gives it solidity. As the adhesions of
the membrane increase, we can less easily distinguish it. It is rare
that in the first dentition the formation of the root is finished as
completely as in the second; its internal cavity remains also very
broad, and the marrow is more developed.


_Second Dentition considered before Cutting._

It is necessary, as in the preceding case, to distinguish the nutritive
phenomena into those which take place before, during and after the
cutting. Before the cutting, we observe by opening the jaw, a row of
dental follicles, corresponding to the row of teeth already formed,
situated below or at the side, and separated from them by little
partitions, the thickness of which is found greater in proportion as it
is examined nearer infancy.

These follicles have precisely the same arrangement as those of the
first dentition; like them they form sacs without an opening, the
alveolar portion of which is attached, and the loose medullary portion
is covered on its surface with the first osseous layers for the crown.
The manner of growth is the same; that is to say, it takes place from
the exterior to the interior, the reverse of the other bones; an
arrangement, which gives the part of the tooth immediately in contact
with foreign bodies, being the first formed, time to acquire the
solidity necessary for its functions.

As the second teeth grow, their vascular system becomes greater, and
that of the old ones diminishes; which arises from this, that the
sensibility weakened in the last, draws to them no more blood, whilst
being raised in the others, it attracts it powerfully. We observe also
that the partition of the sockets diminishes in thickness, and that
the root of the first is destroyed. This double phenomenon does not
appear to be owing to the pressure exerted by the new tooth, as then
the root would spread and become flat only; or if it experienced a
real destruction, we should find the remains of it, which we never do.
It is then probable that, it is by the absorption of the phosphate of
lime, that the partition and root disappear, nearly as we have said the
internal cavities of the cartilaginous bones are formed.

We see from this, that the ossification of the roots of the first teeth
is of short duration; it begins the last and terminates the first.
When it is of but little extent, the teeth become loose, from the want
of insertion. The disappearance of the partitions increases it. It
is at about the age of six or seven years that the shedding of them
commences; this takes place in the order in which they were cut, that
is to say, first the incisors, then the canine, and then the molars.
Observe that the last, which appeared at four years of age, are not
renewed.


_Second Dentition considered at the period of Cutting._

During the cutting of the second teeth, we observe them come out in the
same order as those with which they correspond are detached. 1st. The
eight incisors. 2d. The four canine appear. 3d. In the place of the
first molar, two new ones are cut; these afterwards have the name of
small molars. 4th. The second molar remains, as we have just said; it
is the first of the great ones. 5th. At eight or nine years of age, two
other molars appear in each jaw. 6th. Finally, at eighteen, twenty, or
thirty years, and sometimes later, a third molar is cut; this is called
the dens sapientiæ.

There is then in each jaw sixteen teeth, of which four are incisors,
two canine, two small molars, and three large ones.

Sometimes the second teeth while they are forming, instead of
appropriating to themselves the nutritive substance of the roots of the
first and their partition, leave them untouched; neither are destroyed;
and the second teeth are cut at the side of the first which remain
in their places. When this phenomenon happens, it is usually only to
a single tooth; sometimes, however, it happens to many and even all,
and then there is a double row. In general, the second teeth have a
tendency to go out at the side of the gums. When very obliquely placed,
by a defect of conformation, their crown leans forward or backward;
instead of piercing the jaw, they remain always buried in the sockets.


_Phenomena subsequent to the Cutting of the Second Teeth._

After being cut, the teeth evidently grow, 1st, in length; 2d,
in thickness. It is only the root that is enlarged in the first
direction; the crown preserves always the same dimensions; and if
in old people it appears longer, it is only because the gums have
retracted; a phenomenon which besides we very often observe in persons
who have become thin, in those who have made use of mercury, &c.

The growth in the second direction is not made without, but only
within; the canal of the root and the cavity of the body are constantly
contracting, and are finally obliterated. Then the tooth receiving no
longer the blood or the influence of the nerves, dies and falls out.
But this death appears also to be hastened by the accumulation of
osseous substance, of a very great quantity of the phosphate of lime,
which predominates there so much over the gelatine, that the principle
of life is entirely destroyed, so that in this respect, the shedding of
the teeth exhibits a phenomenon analogous to that of the shedding of
the horns of the herbivorous animals, of the calcareous shell of the
crustaceous ones, &c.

Why has nature given to the life of the teeth a shorter term than to
that of the other bones, which do not cease to exist but with the
other organs, whilst the teeth die a long time before? Is it because
the stomach becoming weak with age, the animals are thence compelled
to nourish themselves in their old age, with soft substances, adapted
to the languid state of the gastric forces? Undoubtedly in man, a
thousand causes, arising especially from the nature of the aliments,
their degree of heat and cold, the manner in which they are cooked,
their infinitely various qualities, hasten the natural period of the
death and the fall of the teeth, because by incessantly exciting
and stimulating these organs, they keep them in a state of constant
activity, which exhausts their life sooner than it otherwise would have
been. Thus a thousand causes arising from society, make the term of the
general life much shorter than that fixed by nature. But in general in
all animals, the death of the teeth precedes that of the other organs,
though they are not under the influence of society, and they masticate
only aliments destined by nature to be in contact with their teeth.

The jaws destitute of teeth in old age, contract; the sockets are
effaced; the texture of the gums becomes firmer, and mastication is
continued, though with more difficulty. In this change of conformation,
the alveolar edge is thrown back; hence the prominence of the chin
before. It diminishes in height; hence the approximation of this part
to the nose, a phenomenon that arises especially from the absence of
the teeth.


V. _Particular Phenomena of the Development of the Sesamoid Bones._

The sesamoid bones exhibit a less marked exception than that of the
teeth, to the general laws of ossification, but one, however, which is
as real.


_General Arrangement of the Sesamoid Bones._

These small bones, commonly of a round form, and of various size, do
not usually exceed that of a pea, except however the patella; they are
in general found only in the extremities; the trunk never has any of
them.

In the superior extremities we hardly see them, except in the hand,
in which the articulation of the thumb with the first bone of the
metacarpus always presents two of them, and in which they are sometimes
found in the analogous articulation of the index finger, rarely in that
of the little one, or in the phalangeal articulation of the thumb.

In the inferior extremities on the contrary, they are numerous and
especially much more evident. Two are seen on each condyle of the
femur, in the tendons of the biceps, behind the knee; in front is the
patella. In the foot, the tendon of the tibialis posticus near its
insertion in the tuberosity of the scaphoid bone, that of the peroneus
longus in its passage under the cuboid, have also sesamoid bones. We
uniformly see two under the metatarso-phalangeal articulations of the
great toe; under most of the analogous articulations of the other toes,
they are also found, though they are more variable. In the phalangeal
articulations I have also seen them many times. In general, the
sesamoid bones exist only in the direction of flexion, which is that
in which the greatest efforts to support are made. In the direction of
extension I know no one but the patella.

These little bones have not, like the others, a separate existence;
they are developed always in a fibrous organ, either in a tendon,
as those of the biceps, the peroneus, the tibialis posticus, as
also the patella; or in a ligament, as all those placed before
the metacarpo-phalangeal articulations, the metatarso-phalangeal
or phalangeal, which have for their basis the great transverse
fibrous fascia, which we have called the anterior ligament of these
articulations.


_Fibro-Cartilaginous State._

The two primitive bases of the sesamoid bones remain for a long
time without exhibiting any rudiments of them, and are at the place
where these bones are to exist as they are everywhere else. Their
organization is generally uniform. Some time after birth, a little
more gelatine than would serve for the nutrition of these two fibrous
bodies begins to be exhaled at the place where the sesamoid bones will
hereafter be found; then arise cartilages, essentially different from
the cartilages of ordinary ossification, which are nearly of the same
nature as those of the extremities of the long bones of adults, whilst
that these belong truly to the class of fibro-cartilaginous substances.
They resemble in their nature the inter-articular fibro-cartilages,
those of the tendinous grooves, &c. These are not cartilages, but
the fibro-cartilages of ossification, of which we distinguish so
much better the fibrous base, as it is nearer the period of their
development that we examine them.


_Osseous State._

Gradually the vessels of these fibro-cartilages, which had only
circulated white fluids, have their sensibility placed in relation with
the blood; this fluid penetrates them; at the same time the phosphate
of lime begins to be deposited in them; then the texture of the cells
is formed in the interior by a mechanism analogous to that of the other
bones; a delicate compact layer is developed on the exterior. But
in the midst of this new bone, the fibrous base always remains; the
fibres of the tendon, above the sesamoid, are continued, if we may so
say, through its substance with those below it; thus the cicatrices of
these bones, when they are fractured, have a peculiar and distinctive
character; it is their fibrous base, which extending itself for their
reunion, produces this difference. We know that the callus of the
patella is not the same as that of the other bones. Often when the
apparatus has not been exactly kept in place, there remains between the
two fragments a fibro-cartilaginous texture as a means of union; now
this texture is the development not only of the cartilaginous portion
of the bone, but also of the portion of the tendon of the extensors,
which makes part of the organization of this bone. The life of the
sesamoid bones partakes almost as much of that of the fibrous as of
that of the osseous system.

As we advance in age, these small bones increase and become more
characterized in the animal economy; oftentimes they are developed very
late, at the age of twenty, thirty, or even forty years. In some old
people they are very large on the foot. I have seen the bodies of two
persons subject to gout, in which they were so developed as probably
to interfere with motion. Was there any connexion between them and this
severe affection? I know only these two facts.

The sesamoid bones elongate their tendons from the centre of motion,
facilitate their sliding upon the bones, defend their articulations and
even contribute to their motions. All those developed in the anterior
ligaments of the metacarpo and metatarso-phalangeal articulations, and
of the phalangeal themselves, contribute also to the motion of these
articulations. A portion of the synovial membrane is spread upon their
face that corresponds with it, and which remains slightly cartilaginous.

The formation of the sesamoid bones is not a mechanical effect of the
pressure of the tendons or the ligaments against the bones, as has been
said, but the result of the laws of ossification. In fact, in the first
supposition, why should all the articulations of the hand and the foot,
other than those pointed out above, being exposed to a motion nearly
equal to the motion of these, be destitute of these bones?



MEDULLARY SYSTEM.


Though the medullary system is only met with in the bones, and
though its principal uses appear to relate entirely to them, yet its
properties and life differ so much from the properties and life of
these organs, that we are compelled to examine them in a separate
manner.

We distinguish two kinds of medullary systems; one occupies the texture
of the cells of the extremities of the long bones, and the whole of the
interior of the short and flat bones; the other is found only in the
middle part of the first; let us examine each separately.


ARTICLE FIRST.

MEDULLARY SYSTEM OF THE FLAT AND SHORT BONES, AND THE EXTREMITIES OF
THE LONG ONES.


I. _Origin and Conformation._

This system appears to be the expansion of the vessels which penetrate
the bones through the foramina of the second order, that is to say,
through those that go to the common texture of the cells. These
vessels having arrived on the internal surface of the cells, divide
ad infinitum and anastomose in a thousand ways. Their interlacing
gives to the interior of the texture of the cells that red appearance
that characterises it, and which is so much the more evident, as it is
examined at an age nearer infancy, because in fact the vascular system
which is very evident at this period, becomes contracted and effaced as
we recede from it.

These are the vessels which, in the section of the bones of the cranium
by the trephine, give to the saw-dust the redness that is observed.
It is these that produce the same phenomenon in the amputation of the
extremity of the limbs. Though in general they remain loaded with blood
at the moment of death, yet we can, as I have often done, accumulate in
them still more by fine injections, which drive before them that which
is found in the vessels, and concentrate it at their extremities; then
the spongy texture of the adult is almost as red as that of the child
which has not been prepared.


II. _Organization._

Authors speak of a delicate membrane that lines the interior of all
the osseous cells, and which they consider to be the exhalant organ of
the medullary fluid. I have never been able, though my researches have
been numerous, to discover a similar membrane. We see only the vascular
elongations of which I have spoken, which, greatly multiplied, appear
in fact to form a membrane, but when examined attentively are found to
be very distinct from each other, not continuous, except at the place
of the anastomoses, and leaving between them many small spaces in which
the bone is not covered, but is in contact with the medullary fluid.

The exhalation then of this fluid appears to arise only from this
vascular net-work, and in this respect it is analogous to that of the
compact substance, which evidently contains no membrane, and the pores
of which are however found filled with this medullary fluid, as is
proved by the combustion of the compact texture and its exposure to the
sun or artificial heat.


III. _Properties._

This vascular net-work has only organic sensibility and insensible
organic contractility, which are necessary for its functions; and it
is this which especially distinguishes it from the medullary system of
the middle part of the long bones, whose animal sensibility is, as we
shall see, very great. Irritate in a living animal the interior of a
short or flat bone, or the extremity of a long one, no sign of animal
sensibility is manifested. Sawing the cranium, the condyles of the
femur and the head of the humerus is not painful.

Injuries of this system when they are very great may produce necrosis
of the bone, and the formation of a new osseous substance at the
expense of the periosteum; but if a small portion only is affected,
this phenomenon does not take place. I have many times perforated
transversely with a gimblet the extremity of a long bone of an animal,
and afterwards passed a red hot iron through the opening; the animal
has always recovered without necrosis; the articulation has only
remained swelled, and much injured in its motions, and some scales have
come from it during the suppuration.


IV. _Development._

The vascular net-work which forms this medullary system, exists in the
cartilaginous state; but then, on the one hand, it does not admit the
red portion of the blood, and on the other, the interstices of its
meshes are found so filled with gelatine, that the cartilage appears
homogeneous. At the period of ossification, the red blood penetrates
on one side of these vessels, whilst on the other they become evident
from the absorption of gelatine at the place of these cells, upon the
internal surface of which they ramify.

In the fœtus and the first age, this medullary system has a remarkable
arrangement. It contains scarcely any of this oily fluid, from which it
borrows its name, and which afterwards fills in so great a proportion
the interstices of the texture of the cells of the different bones;
by examining these organs comparatively in the different ages, I
easily convinced myself of this. 1st. Exposed to a considerable degree
of heat, the texture of the cells of the bones of an adult has an
abundance of oily fluid flow from them. From the same experiment in the
fœtus, there only follows a drying of this texture by the evaporation
of the fluids which enter it. 2d. If we burn the extremity of a long
bone of an adult, the combustion is spontaneously supported by the
oily fluid that escapes from the pores of the second species, and
which keeps up the flame until it is exhausted. In the fœtus, the bone
ceases to burn when we take it from the fire, because the fluids it
contains do not support combustion. 3d. Nothing is more difficult than
to keep the bones of the adult white, because the oil that is in their
interstices always yellows them a little. In the fœtus and the infant,
in whom this cause does not exist, the bones are easily kept white.
4th. By ebullition, we extract scarcely any oil from the texture of
the cells in the first age; much swims on the water in which we have
boiled this texture in the following ages. In general, the, fœtus
appears to want this oil entirely; it is formed after its birth, and
its proportion is constantly increasing until complete growth. What
fluid supplies its place in the first years? At first a large quantity
of blood; for in general the redness of the medullary system is in the
inverse ratio of the oil that is found in it; but the interstices of
the cells appear moreover to be moistened by a fluid with which we are
unacquainted, and which evaporates, as I have said, when we expose to
the fire the bones of a fœtus.


ARTICLE SECOND.

MEDULLARY SYSTEM OF THE MIDDLE OF THE LONG BONES.

This system differs essentially from the preceding in its nature, its
properties, its functions, &c. It occupies the centre of the long
bones, whose great cavity it fills.


I. _Conformation._

Each of the organs from the whole of which it results, exhibits it
under the form of a delicate membrane, lining the whole cavity, folded
a great number of times, giving origin to many elongations, of which
some cover the fine threads of the texture of the cells which are met
with in this cavity, others pass, without adhering to any osseous
portion, from one side of the membrane to the other, and of which all
form numerous cells in which the marrow is contained.

We can then form of this organ an idea analogous to that which the
cellular organ gives us; viz. that of a spongy body with communicating
cells. The place that it occupies, gives to it as a whole, a
cylindrical form.

It appears that at the two extremities of the canal, the cells or
membranes do not open into those of the texture of the cells, and that
the medullary fluid of the preceding system does not communicate with
the marrow of this. In fact, the line of demarcation which separates
them is evident; they do not mix in a gradual manner. Air injected from
one side of the medullary cylinder, only penetrates with difficulty and
by tearing the membrane, into the texture of the cells of the opposite
extremity of the bone; yet, notwithstanding these considerations, I
confess that the question is not fully settled. The transudations
in dead bodies have no influence in deciding it, on account of the
permeability that our parts acquire after death.


II. _Organization._

The texture of the medullary membrane is very little known, because its
extreme tenuity conceals it from our researches; for it is only in the
bones of ricketty subjects, that its morbid increase in thickness has
permitted me to trace it accurately. It has the appearance of cellular
texture; yet its properties and its nature are very different from
this texture; it cannot be referred to any of the three classes of
membranes, the serous, the fibrous or the mucous. Some have pretended
that it was an expansion of the periosteum, which had passed through
the numerous foramina by which the bone is perforated, and entered
into the medullary cavity; but the least parallel made between these
membranes is sufficient to make us see that they are essentially
different in their functions, vital forces, &c. and cannot have the
same texture. A principal vessel penetrates the medullary membrane; it
is the artery, which enters by the only, but very large foramen, which
is seen on the body of the long bones; the two branches of this artery
and those of the corresponding vein, ramify in an opposite direction in
the medullary cylinder, and by their innumerable branches give to it a
very evident reddish colour, that disappears with age. The extremities
borrow their vessels from those of the neighbouring texture of the
cells. We cannot trace any nerve there. Such is sometimes the abundance
of the fluids which penetrate this membrane, and its extreme tenuity,
that it might be said not to exist. To be convinced of its existence,
expose the cylinder that it forms to the intense action of heat; it
contracts, has the horny hardening immediately like all the solids, and
thus becomes more apparent.


III. _Properties._

The properties of texture are very well marked in the medullary organ.
1st. The spina ventosa in which this organ is distended in a very
evident manner with the body of the bone, proves its extensibility. 2d.
The contractility of texture is made apparent by the contraction of
the cells, after the amputation of the middle part of a long bone, a
contraction which prevents the flow of marrow, which without it would
take place on account of the communication of these cells.

It is probable that the insensible organic contractility, which is
then brought into action by the contact of the air upon this membrane
which contracts from its irritation, has an influence also upon this
phenomenon; for this membrane evidently has this kind of contractility,
as well as the corresponding sensibility.

The animal sensibility is developed in it to an extreme degree in
the natural state; the most acute pains are the result of the action
of the saw upon it in amputation, of the introduction of a probe, of
the injection of an irritating fluid into the medullary cavity, or
of any other means which powerfully excite it. I do not speak of the
pains of the bones in spina ventosa, syphilis, &c.; as the membrane is
not then in a natural state, we cannot infer from them what kind of
vital forces it is naturally endowed with. I have observed that the
sensibility is greater, as we approach the centre of the bone with
the probe when pushed into living animals. At the extremity of the
medullary canal this sensibility is small; in the middle, the division
of the bone is very painful. Whence arises this inequality of sensitive
power, this decrease from the centre to the extremities? I know not.
The medullary system evidently does not possess animal contractility
and sensible organic contractility.

It is evident from this view of the vital forces which animate this
system, that the life is much more active in it than in the osseous
system, that its vital phenomena are consequently more rapid, that
they have not that chronic course which characterizes all the diseases
of the bones and that they respond more promptly to the sympathetic
excitements of other organs. I am persuaded that many of the uncertain
pains which we usually refer to the bones in diseases, have their seat
rather in the medullary system, in that of the middle of the long
bones especially; observe in fact that most of these pains are fixed
in the middle of the limbs, and that they are really in the direction
of that system. The medullary system of the extremities of the long
bones, and of the flat and short ones, certainly enjoys much more
vital energy than the osseous texture itself; inflammation is much
more easily developed in it, its effects are more promptly shown. Who
does not know that caries is so much the more rapid, in proportion to
the quantity of the texture of the cells that exists in the bones? It
is not this texture, which by its nature, has an influence upon this
phenomenon; but it is, because the more abundant it is, the more the
medullary system predominates in it; now as this participates in all
its affections, it imprints upon them a rapidity which they have not in
the compact texture in which it does not exist.


IV. _Development._

This membrane exists in the cartilaginous state of the middle part of
the long bones; but then it serves for the nutritive parenchyma to the
gelatine that is exhaled there, and which, accumulated in very great
quantity in its cells, renders the bone homogeneous in appearance,
and prevents it from being distinguished. When ossification takes
place, this substance is absorbed; the medullary cavity is formed; the
medullary membrane is bare; the blood enters its vessels, till then
permeable only by white fluids, because its kind of organic sensibility
changes. Instead of receiving gelatine in its cells, it is the marrow
or another fluid that it admits there, a phenomenon also dependant upon
this change of organic sensibility. Hence an external form wholly new,
a new organ in appearance, whilst in reality it is not the organ which
changes, but the fluid that is deposited in it. The same phenomenon
nearly is observed in the formation of callus, in which the portion
of the medullary membrane corresponding to the fracture is at first
cartilaginous, then osseous, and finally becomes what it was originally.

The exhalation of the marrow does not commence when the blood enters
the medullary canal, or rather it commences, but I have found that
it is wholly different from what it is afterwards in the adult. The
proportion of oily substance is almost nothing in it, compared to what
we have seen in the medullary fluid. 1st. It has a mucilaginous and
reddish appearance; pressed between the fingers, it does not give out
an oil as in the adult, but a fluid like gelatine. 2d. By comparing the
water in which the marrow of the two ages has been boiled, we cannot
see in the first, as in the other, many oily drops floating on the
surface. 3d. Exposed to the action of fire, the middle of a long bone
lets fall an infinite number of small burning drops, very beautiful, of
a blue tinge and which are furnished by the marrow, which burns after
being melted. Nothing similar to this is observed in the fœtus. 4th. We
know that the taste of the marrow is very different in young animals,
in veal, for example, from what it is in adult ones. It is insipid,
disagreeable, little esteemed in the first. 5th. I have observed that
the marrow of children soon putrifies, becomes green, then black, if
their fresh bones have been kept for some time in the air. The odour of
this putrid marrow is very fetid. Preserve, on the contrary, for some
time the bones of an adult, you will observe that their marrow turns
rancid, and becomes of a deep yellow colour, like all fat that has been
some time kept. In general the action of the air is wholly different
upon the medullary organ, in the first and in the after ages. What is
the fluid which this organ especially separates in the fœtus and in
childhood, and which then takes the place of the oily substance? It is
an interesting object of research. Do the vulgar, who connect the idea
of fat with that of marrow, know this phenomenon, when they say that
children have yet no marrow in the bones? This absence of medullary fat
in the fœtus, essentially distinguishes the marrow from the ordinary
fat, which, at this age, is already very abundant.


_Functions._

The first and principal use of the medullary organ is to separate
the marrow from the mass of blood by means of exhalation, for it has
no glands, and afterwards carry it into it again by absorption, when
it has remained for a certain time in its reservoir. This double
phenomenon is very analogous to that which takes place in regard to the
fat, for which we see that there are two orders of vessels distinct
from the sanguineous, that enter its texture; it is not possible
however to demonstrate them anatomically.

Is the activity of the exhalants varied by exercise or rest, heat or
cold, corpulency or emaciation? We have not any precise experiment
upon this subject, though numerous conjectures have been made. But we
know that in phthisis, dropsy and marasmus, and in general, in all
those states of the body in which general debility is carried to an
extreme by the slow and gradual loss of the forces, the marrow, like
the other fluids as well as the solids, is changed, loses its essential
characters, its consistence and takes an appearance wholly different,
without however the medullary membrane experiencing any lesion, or
being thickened. I have never observed this lesion except in rickets.
The appearance of the marrow in these diseases is mucilaginous,
gelatinous, similar to what is seen in the fœtus, with the difference
of the redness, which is produced in the first age, by the great number
of blood vessels.

The medullary membrane has a direct relation with the nutrition of the
bone, a relation which has been proved by the beautiful experiments of
Trojat, from which it follows that the destruction of this membrane
produces the death of the bone, which has necrosis and is replaced
by new bone, for which the periosteum serves for the nutritive
parenchyma. These experiments are usually made by sawing a long bone
at its extremity, and introducing into the medullary cavity a red hot
probe, which destroys the whole organization. Soon after the periosteum
swells, inflames and has an extreme sensibility to the external touch.
This sensibility is gradually lessened; the inflammation disappears.
A considerable quantity of gelatine penetrates the internal layers of
this membrane, which becomes a cartilaginous sac, with which the bone
is covered. At the end of some time, which varies according to the
class of animals subjected to the experiment, according to their age,
their temperament and other causes, the vascular system, destroyed on
the interior of the canal, and expended wholly upon the periosteum,
deposits there the phosphate of lime destined for the bone. To the
cartilaginous cylinder then succeeds the osseous one. The bone within
has no connexion with the life of the living body that surrounds it
on all sides. There are then in artificial ossifications three very
distinct periods, 1st, swelling and inflammation of the periosteum;
2d, cartilaginous state of the internal layers of this membrane; 3d,
osseous state. Besides, these two last states are not as regular and
distinct, nor as easy to be observed as in natural ossification.

Does the medullary membrane serve indirectly to furnish a part of
the synovia by the transudation of the marrow through the extremity
of the long bones? Most authors assert it. We know at the present
day, what must be thought of these mechanical transudations, which
are observed in dead bodies, but which are repugnant to the known
phenomena of vitality; besides, the following experiment leaves no
doubt upon this point. I have opened upon the sides two long bones of
one of the hind legs of a dog, so as to pass in a red hot probe, which
having been carried in several times, completely destroyed the two
medullary systems; necrosis has been pretty soon the consequence of
this experiment, and yet the articulation between the two bones with
necrosis, has continued to receive synovia as usual, a circumstance
that would not have happened, if the transudation of the marrow was
necessary to the production of this fluid. Who does not know, on the
other hand, that in diseases of the articulations in which the synovia
is altered and vitiated, the marrow of the corresponding bones is
almost always in a perfectly sound state, and that vice versa, in the
diseases which attack the medullary organ, the synovia is not altered
in its nature like the fluid which this organ contains in its cells?



CARTILAGINOUS SYSTEM.


The word cartilage is employed too vaguely. It designates, in the
common acceptation, bodies whose organization differ essentially.
The cartilages of the nose and those of the articular surfaces have
certainly but a very remote analogy between them; it is necessary
then to establish a line of demarcation. I have endeavoured to do
it by making two systems of them; one comprehends the cartilages
properly so called, the other, the fibro-cartilaginous substances,
such as those that are between the vertebræ, those in the middle of
some articulations, &c. As this last is a compound of the fibrous and
cartilaginous system, I shall not treat of it until I have spoken of
the fibrous system.

By thus limiting the sense of the word cartilage, it gives us the idea
of a hard, elastic, white substance, having an inorganic appearance,
though it has a real organization. We find this animal substance in
different parts of the body; it is met with especially, 1st, at the
articular extremities of the moveable bones; 2d, on the articular
surfaces of the immoveable bones; 3d, on the parietes of certain
cavities, which it contributes in great measure to form; such are the
cartilages of the nasal partition, of the ribs, the larynx, &c. Hence
three different classes, which exhibit varieties in their forms, in
their organization, &c.


ARTICLE FIRST.

OF THE FORMS OF THE CARTILAGINOUS SYSTEM.

The forms of the cartilages vary according to the class to which the
cartilage belongs.


I. _Forms of the Cartilages of the Moveable Articulations._

In every moveable articulation, there is at each osseous extremity,
a cartilage which covers this extremity, which facilitates by its
suppleness the motion of the two bones, the very hard substance of
which would occasion by friction too great a shock; which reflects
by its elasticity a considerable part of the motion, thus made more
extensive; which breaks, by yielding a little, the violence of the
shocks the limbs experience, and which thus render these shocks less
dangerous.

The general character of the internal conformation peculiar to these
cartilages is that of being always less thick than broad, of having
a thickness which is in the ratio of their breadth: so that the
cartilages of the great articulations exceed in this respect two,
three, or four times even, those of the smaller articulations; and
these cartilages are moulded upon the articular forms and exhibit two
faces and a circumference.

One of these faces adheres to the bone; it unites with it so
intimately, that fractures take place any where else rather than
here. The means of union are not exactly known; this is certain,
that the cartilage is not an elongation, a continuation of the
cartilaginous parenchyma of the bone; the fibres of this parenchyma
are not continuous with those of the cartilages. If it really
was so, by removing from a long bone, fresh and clothed with its
cartilage, the phosphate of lime which penetrates it, we should see
this continuity, the bone and the cartilage would not differ; now I
have constantly observed that in this experiment the action of the
acid detaches the cartilage from the bone, either in fragments or
as a whole. We see the cartilaginous fibres of the bone deprived of
its saline base, terminating evidently on the convex surface which
the cartilage embraces; no solution of continuity has taken place.
In general, the appearance of the cartilaginous parenchyma, separate
from its calcareous portion, is wholly different from that of a true
cartilage., I presume that this difference is owing to the quantity of
gelatine, which is greater in the second than in the first. The action
of the acids, especially the nitric, is the best means of separating
a cartilage from its osseous head; maceration does not produce this
phenomenon under a great length of time; in ebullition, as the gelatine
melts, it is less apparent.

The surface of the cartilage opposite to the bone, is intimately united
to the synovial membrane of the articulation. It borrows from it the
polish which it has; for wherever these substances do not correspond
to this membrane, they lose this character, as we see in the larynx,
in the cartilages of the ribs, &c. Here the means of adhesion is an
extremely compact cellular texture, which neither maceration nor
dissection can remove in layers. As the synovial membrane is wholly
formed from this texture, it appears that upon the cartilage it is
only an elongation of that which, after having contributed to the
structure of this organ, is condensed upon its surface and organized as
a membrane.

The circumference of the cartilages of which we are treating,
terminates insensibly upon the osseous surface; it ceases at the place,
where the synovial membrane quits the bone to be reflected.

The two corresponding cartilages of a moveable articulation are so
arranged and adapted to each other, that in the medium position of
the articulation, they touch exactly at all their points; now we know
that the medium position of an articulation is that in which the bone
inclines in neither direction, in which all the muscles contracting
uniformly and making an equal resistance, keep it equally from
extension and flexion, from adduction and abduction, &c. &c. and hold
it in the exact medium. It is this position which the limbs take, when
the will does not direct the muscular effort, as for example, in the
fœtus, in sleep, in rest, &c.; this is what some convulsions produce,
in which all the muscles of a limb are agitated with an equal effort,
by an extraordinary influx of the nervous power, &c. In no other
position does the contact of the two articular cartilages take place at
all their points; one portion of the surface of each always pushes with
more or less force the parts surrounding the articulation, and distends
them. The softness of the cartilaginous texture renders less painful
this pressure, which would be distressing in the great motions, if the
bones preserved their hardness at the extremity of the lever which they
represent.

The cartilaginous forms of which we are treating, besides these common
characters, have others peculiar to each kind of moveable articulations.

1st. In the first kind, the convex crust which covers the osseous head,
is thick in the centre, but not at the circumference. An opposite
arrangement takes place in the concave crust which receives this head;
often even as in the humerus, and the femur, the thickness of this
crust is increased at its circumference by a fibro-cartilaginous band.
In this way, the effort is borne unequally by the two cartilages; but
the uniformity of contact is established.

2d. In the second kind, which differs from the first by the absence
of the motion of rotation, though in general a convexity is also
received into a concavity, the arrangement for both the cartilages is
nearly the same. Yet if two convex surfaces slide upon each other, an
example of which we have in the condyle of the jaw and the transverse
apophysis, then the cartilage is constantly becoming thinner towards
the circumference of each; but then an inter-articular cartilage, thick
at the circumference, thin in the middle, supplies the place of this
arrangement, and establishes at all points a contact, which, without
it, would only take place at the centre.

3d. In the third kind, the cartilaginous crust which covers the
prominences and depressions, which reciprocally receive each other upon
the extremities of the two bones, exhibits nearly an uniform thickness,
as we see at the elbow, the knee, &c.; so that the pressure comes
equally upon the whole articular surface.

4th. In the fourth and fifth kinds, the cartilaginous crusts moulded
on the form of the osseous surfaces, have also a thickness nearly
uniform at all points; I have found upon the bones of an adult, that
this thickness is a line and a half in the radio-cubital articulation
and that of the atlas, and a line in the carpal and metacarpal
articulations.


II. _Forms of the Cartilages of the Immoveable Articulations._

The cartilages are found only in two kinds of immoveable articulations,
viz. in those with surfaces in juxta-position and those with indented
surfaces. They form in all a very thin layer, continued upon both bones
which articulate together, arising from their osseous portion, like
those described before, being of the same nature as it, and forming a
band so much the more close as we advance in age.

On the head these cartilages are very numerous; those of the cranium
have more thickness on the convex than on the concave side, hence the
more rapid disappearance of sutures in the last than in the first
direction.

Wherever they are found, they contribute to unite the bones which form
the cavities; hence, as we have said, there is less danger for these
from external bodies, since the motion lost then in part in their soft
texture, produces a less effect than if the cavity was only one osseous
piece.

It appears that these cartilages have much more affinity to the
phosphate of lime, than those of the moveable articulations, which
rarely ossify, whilst at an advanced age these always become osseous,
of which the cranium especially furnishes us examples. I would observe
however that the cartilages of the indented surfaces have much more
tendency to ossification than those of the surfaces in juxta-position.
At least it is more common to see the parietal bones united with the
occipital and frontal, than to see the union of the ossa maxillaria,
ossa palati, &c.


III. _Forms of the Cartilages of the Cavities._

The cartilages of the cavities have two different forms according to
the parts which they contribute to form. They are, 1st, long, as in the
ribs; 2d, flat, as in the larynx, the nasal partition, &c.

All are covered on the exterior with a fibrous membrane like the
periosteum, and in which different muscles are inserted. In order to
see this membrane it is necessary to macerate the cartilage for a day
or two; it then becomes white and very evident in its thickness, and
the direction of its fibres. The cartilages of the cavities do not
exhibit the numerous foramina which are seen in the bones, because the
blood vessels do not penetrate them. But few eminences and depressions
are observed in them. We can hardly consider their forms in a general
manner, because destined to very different uses, they have but little
resemblance in their conformation.


ARTICLE SECOND.

ORGANIZATION OF THE CARTILAGINOUS SYSTEM.

In examining a cartilage in its interior, it is difficult to recognize
in it an organic texture; there is one however, which is composed of a
peculiar texture and of common textures.


I. _Texture peculiar to the Cartilaginous System._

The peculiar cartilaginous texture exhibits an interlacing of fibres so
compact, that it appears at first view homogeneous, formed into a mass
of gelatine, without order and without any particular direction. Yet
with a little attention we distinguish longitudinal fibres, which are
crossed by transverse and oblique ones.

These fibres are more apparent in the cartilages of the moveable
osseous extremities than in the others. They have infinitely less
suppleness than the fibres of the fibro-cartilaginous substances; thus
these bend without breaking, whilst the first break when they are
bent considerably; the place of the rupture is smooth, with but few
inequalities.

The cartilaginous texture is remarkable for many characters which
distinguish it from the others. Next to the osseous texture, no one so
long resists putrefaction and maceration. In the midst of a dead body
wholly putrid, we find this texture almost untouched, preserving its
appearance, its structure, and even oftentimes its natural whiteness.
The same thing is frequently seen in gangrenous limbs in the living
body. I have kept cartilaginous substances a very long time in water,
which have not become altered, except a little in their colour. It
would require more than a year perhaps, to reduce them to that soft,
mucous, liquid pulp, to which maceration reduces most of the organs.

The cartilaginous texture contracts under the very powerful action
of caloric, like all the other textures; yet this phenomenon is not
apparent in the thyroid cartilage on account of its thickness, nor in
the cartilages that encrust the bones, on account of their adhesion
to these bones. But if we cut one in fine layers, and the others in
slices, and plunge them into boiling water, they crisp up immediately
and with force.

Exposed to drying, the cartilaginous texture becomes yellow, acquires
a semi-transparency analogous to that of the tendons and dried
ligaments; it becomes hard, contracts, diminishes in size, and loses
its elasticity as it becomes hard.

Ebullition also gives it at first a yellow colour, then it cracks it
upon the articular extremities, breaks it in different places, and
raises it by layers which it softens, and which finally it melts almost
completely to a small residue, which does not appear to be gelatinous.
The softening of the cartilaginous texture renders it much more fit to
be dissolved by the digestive juices than it naturally is. Swallowed
raw, the cartilages would remain a long time in the stomach, whilst
they are very easily digested when cooked; this is one of the very
great advantages of the boiling of meat. In different experiments made
upon digestion, I have found portions of cartilages still untouched in
the stomach of dogs, whilst the flesh was already reduced to a pulp.

In certain cases, the cartilaginous texture is singularly altered.
In the diseases of the articulation of the hip, it assumes an aspect
wholly different; it is a soft substance, like lard, with very distinct
vessels, sometimes with very evident fibres, having a size double,
quadruple what is natural, and filling the cotyloid cavity. I have
observed that then they do not become yellow, do not melt by ebullition
and consequently are not gelatinous. In the same diseases, I have
found the cartilaginous texture, upon the femur and the ilium, not
only ossified, but changed into a substance exactly like ivory; I have
preserved these two pieces.

When the cartilages become osseous, there is developed in their middle
a texture analogous to that of the texture of the cells of the bones,
in which the interlaced fibres leave between them very distinct spaces,
and in which is deposited a kind of medullary fluid. This observation
is especially applicable to those of the cavities, of the larynx, of
the thorax, &c.


II. _Parts common to the Organization of the Cartilaginous System._

There is cellular texture in the cartilages, though the want of
interstices between their fibres, renders it very difficult to
distinguish it in a natural state; in fact the development of fleshy
granulations in wounds in which they are concerned, ebullition which,
after having removed the gelatine, leaves a membranous and cellular
residue, prove abundantly the existence of this texture, which we see
besides in a very evident manner in some morbid states, in which the
gelatine less copiously deposited in the cartilages, ceases to give
them their usual hardness and leaves there a soft texture, often like
sponge.

We do not discover any blood vessels in the cartilages. The exhalant
system circulates only white fluids in them; but as this system is
continuous with the arteries of the neighbouring parts, when the
organic sensibility is raised in it by morbid irritations, and it thus
becomes in relation with the red globules of the blood, these globules
easily pass into it, and hence the redness the cartilages then have, as
we see in their inflammation, in wounds of them, &c. It is this same
phenomenon that we observe upon an inflamed conjunctiva, &c. When the
irritating cause has ceased, the sensibility resumes its natural type,
the red globules then become heterogeneous to the cartilage, which
again becomes white.

We are ignorant of the nature of the white fluids which usually
circulate in the vascular system of the cartilages. These fluids very
easily become the vehicle of the bile, or at least of its colouring
matter, which is spread through the animal economy in jaundice. We
observe almost uniformly, that in this disease the cartilages are of
a yellow colour, like all the other parts; the colour is more evident
on their surface than in their texture, though it exists there. By
opening a moveable articulation, the bilious appearance is commonly
found as great there as upon the skin. Besides, all the parts, which
like them, receive but few or no red globules in the ordinary state,
are also found very evidently coloured. The tendons, the conjunctiva,
the internal membrane of the arteries, &c. are examples of this. I have
remarked in two subjects whose thyroid cartilages were ossified in the
middle, that the yellow colour was much brighter in the osseous than
in the cartilaginous portion. I do not know that nerves have ever been
traced in the cartilages.


ARTICLE THIRD.

PROPERTIES OF THE CARTILAGINOUS SYSTEM.


I. _Physical Properties._

Elasticity is a property generally extended to all organic and
inorganic bodies. Among the first, it appears, that vegetables are
endowed with it in the greater number of their organs; that animals,
almost all of whose parts are soft, have some which return to their
original state after having been stretched or compressed. Among these,
the cartilages hold one of the first ranks in man. Their elasticity
is very great, especially in the adult age, when their consistence
is between the softness, which characterizes them in childhood, and
the hardness, which is their attendant in old age. These two last
properties are in fact not favourable to the elastic power.

If we plunge a scalpel into a cartilage, the edges of the divided place
re-act upon it and expel it. Pressed against a resisting body, the
cartilaginous extremity of a long bone becomes flat and resumes its
form when the compression ceases. The edges of the thyroid cartilage,
when it is cut longitudinally in the operation of bronchotomy,
immediately approximate each other. The division of the cricoid ring
exhibits the same phenomenon. The cartilages of the last ribs, when
forced in towards the abdomen, come out of themselves, &c. &c. All
these phenomena are the evident result of an elastic power. Thus nature
has placed the cartilages wherever, to produce her phenomena, there
is a necessity of uniting a physical to the vital forces, as in the
larynx, in the nasal septum, in order to produce a sort of vibration
in the passage of the air, at the extremity of the ribs, in order to
be the seat of a species of twisting necessary to the mechanical part
of respiration, at the articular extremities, in order to diminish the
force of blows, &c.

It appears that the vital activity renders this property greater,
which however remains very apparent after death. I presume that this
is owing to the great quantity of gelatine they contain. 1st. We know
that this substance possesses it in a very high degree, as is proved
by the tremulous motion of jelly after it has become cold, by the
examination of various animal glues, &c. 2d. If by ebullition we remove
this substance from the cartilages, the nutritive parenchyma remains
flaccid and soft. 3d. As the gelatine diminishes in our organs, the
elasticity in them is less, as we see by examining the decrease of
this property from the cartilages in which it predominates, to the
fibro-cartilaginous organs in which it is in a smaller proportion, and
to the fibrous bodies in which it is still less. It must be confessed
however that many very gelatinous bodies, exhibit but very slight
traces of elasticity; the skin is an example of this, and so are the
tendons. Can the same substance, as it is differently operated upon by
the organic laws, become the seat of properties wholly dissimilar?


II. _Properties of Texture._

The cartilages are perhaps of all the organs, those in which the
extensibility and contractility of texture are the least developed. We
see them rarely distended and elongated; they break first. Diseases
do not exhibit in the larynx those dilations so common in the other
cavities, even the osseous ones. When divided, the edges, far from
separating as in the skin, in a muscle, &c. approximate each other, as
we have seen, by the effect of elasticity; we might say that this last
property was accumulated in the cartilages at the expense of those of
texture.


III. _Vital Properties._

The vital properties are also very obscure in them. There is no animal
sensibility in the natural state; it is only when inflammation or some
other cause raises their organic sensibility, a sensibility which their
functions necessarily suppose, it is only then, I say, that the brain
perceives painfully the different irritations of which these organs
are the seat. This becomes manifest, especially when foreign bodies
are formed in the articulations, which suffer from their presence or
are insensible to them, according as they irritate or not by their
position, the cartilaginous extremities. There is neither animal nor
sensible organic contractility in the cartilages; the insensible
organic or tone alone exists in them, and this not in a great degree.

The sympathies are obscure, almost wanting in the cartilaginous system.
I do not know that in the acute affections of the different organs,
we observe sympathetic phenomena of sensibility or contractility in
them. They remain tranquil in the midst of the general derangement
which affects the other systems in this sort of diseases. In chronic
affections even, they experience but little alteration; examine, for
example, comparatively, the body of a man that has died a violent
death, which has left his organs untouched, and that of one who has
died from phthisis, dropsy, cancer, &c. you will perceive between
almost all their organs a striking difference; the aspect of the
muscles, of the mucous and serous surfaces, of the vessels, the nerves,
&c. is entirely changed by the slow alteration they have undergone
in the second; in the midst of these alterations the cartilages are
unchanged, their appearance is almost the same as in a natural state.


_Character of the Vital Properties._

From what has been said, it is evident that the cartilaginous life
can have but little activity, that all the morbid phenomena must
be characterized in these organs by a peculiar slowness, and that
inflammation, for example, must always have in the cartilages, as in
the bones, a chronic progress; this is rendered very clear by the
following experiment. Lay bare a cartilage, divide it, and afterwards
bring it in contact with a portion of a muscle, the skin, &c. also
divided at their surface; the reunion does not take place, or at
least not until a very long time. Why? because the life of the muscle
or the skin being much more active than that of the cartilages, the
inflammation of the first organs will be much more rapid than that
of the second, and consequently the first inflammatory period of one
will correspond to the last of the others. Now the reunion is so much
the easier as the inflammatory periods correspond the more exactly
in the two divided parts that are in contact. Hence why two parts of
the same organ unite much more easily than two surfaces belonging to
different organs. Hence why the greater the analogy in the lives of
the two organs, the greater the facility with which they unite; why
the difficulties increase as the differences of life become greater.
Two osseous surfaces in contact require thirty or forty days to unite;
the two edges of a cutaneous wound unite in two or three days. If you
attempt to render continuous two organs thus unlike in their mode
of cicatrization, by putting them in contact, you will succeed but
slowly. Cover with skin the osseous extremity of an amputated stump;
this will be in a state of suppuration, before the bone has hardly
begun to soften; thus good practitioners have abandoned these pretended
unions by the first intention, so much boasted of, after amputation
by the flap operation. These unions would no doubt take place, if the
life of the organs which enter into the composition of the flap was the
same. But with the diversity of these muscular, osseous, tendinous,
cellular, nervous organs, &c. it requires a long time for all their
lives to be placed as it were in equilibrium, and for these organs to
agglutinate at their divided extremities. I have already observed that
the division of inflammations into acute and chronic gives physicians
an inexact idea; for the duration of the inflammatory phenomena in the
organs is wholly relative to their degree of life. An inflammation
of the cellular texture and of the skin is acute, when it lasts but
a few days; it is chronic when it continues forty or fifty days; in
a cartilage, this last period may be that of an acute inflammation,
whilst a duration of many months is necessary to make it chronic, as
the diseases of the joints exhibit frequent examples.

The natural functions, as well as the morbid affections, have this
slowness of the vital phenomena of the cartilages. The constant
composition and decomposition, which their nutrition supposes, is not
rapid. It requires a long time for nutritive substances to combine
with them. I am persuaded that in animals which die suddenly from the
effects of a carbuncle and whose muscles, glands, membranes, &c. almost
instantly penetrated with the deleterious principles by the nutritive
motion of composition, present an aliment so injurious, I am persuaded,
I say, that these injurious principles not yet having penetrated the
cartilages, these might be digested without danger. It is to the
slowness of the motion of decomposition that must be attributed the
slowness of the resolution of cartilaginous swellings; for tumours are
resolved by the same laws that decompose our organs, as they are formed
by the same laws that preside over their composition.

The cartilages and the analogous organs, are to the other parts of the
economy, as it respects their vitality, what the zoophytes and other
animals with a capillary circulation only, are to the animals better
organized, to those with a general circulation and those that have a
heart with a double ventricle. As much as life considered in general
in the series of beings that it animates, presents a difference in
its activity, so much it differs in the same respect, examined in
particular in the organs of each of these beings.


ARTICLE FOURTH.

DEVELOPMENT OF THE CARTILAGINOUS SYSTEM.

The osseous and cartilaginous systems are confounded in the embryo; as
the first is developed, the second contracts; the latter very evidently
has gelatine for its principal base; I shall not return to the proofs
that have demonstrated it in the osseous system.

I have shown, in speaking of that system, how the cellular and vascular
parenchyma, existing at first alone and constituting the mucous state,
is penetrated afterwards with this base, which forms the cartilage. The
primitive mode of the formation of these organs is then already known.
Let us see how its development continues.


I. _State of the Cartilaginous System in the first age._

As ossification advances in the bones and gelatine is consequently
carried to them in less quantity, it seems that it goes more abundantly
to the articular surfaces; for the cartilages that are met with,
then lose their primitive softness, and have a consistence that is
constantly increasing. Yet much more gelatine leaves the bones, than
is carried to the cartilages; so that we may say that this substance
is continually diminishing, in the organs, in proportion as we advance
in age. We know that it is the parts of young animals particularly,
that are selected to make glue, jelly, &c. The articular cartilages
at this period exhibit a phenomenon that I have frequently noticed in
my experiments; when we macerate them in water for two or three days,
they take a very evident red colour. This colour does not penetrate
deeply; but if we cut the cartilage in many places so as to bring the
fluid in contact with its interior, the whole of it becomes red. The
cartilages of ossification exhibit the same phenomenon, which becomes
less conspicuous as we advance in age; so that in adults generally,
the cartilages do not lose their white colour by maceration. In some
however they take a reddish tinge which is infinitely less bright than
in the fœtus. Whence arises this phenomenon? Does the water give to the
cartilage the cause of its colour, or does it take from it by solution
certain substances which prevented this colour from being developed?
Whatever may be the cause, none of the organs of articulation redden in
this way; all on the contrary, the synovial, the ligaments, &c. become
whiter.

There is usually no sensible demarcation between the cartilage that is
to become bone, and that which is to remain as it is; sometimes however
on the one hand we observe it a more dull colour at the extremity of
the bones, whilst on the other, we never discover the reddish streaks,
which are so frequently seen irregularly scattered on the cartilages of
ossification.

As long as ossification continues, there is between the cartilage and
the osseous portion already formed, a very evident vascular layer, and
it is extremely easy to separate these two portions, which adhere but
slightly to each other. We observe also on the surface of each when
they are separated, several inequalities, projections and depressions
reciprocally adapted to each other. It is the want of adhesion of the
cartilaginous and osseous portions, before complete ossification,
which has no doubt given rise to all that has been written upon the
separation of the epiphyses, a separation which the observations of
modern surgeons have rarely confirmed.

As the calcareous substance arrives at the extremities of the bone, the
vessels gradually disappear, and the adhesions increase. Finally, the
ossification being finished, there is no longer, on the one hand, an
evident vascular net-work between the cartilage and the bone; and on
the other, their union is such, that all rupture between them is almost
impossible. These two characters especially distinguish the relation
of the cartilage of ossification with the bone, from that of the real
cartilage with the same bone. I have observed also that almost always
above its union with the osseous portion, the cartilage of ossification
has less whiteness, a deeper tinge, which extends the distance of two
or three lines, and whose difference is often very considerable; this
is the forerunner of the access of the blood. This arrangement does not
exist in the cartilage of the bones of the adult.

We attribute commonly to the articular motions, the want of
ossification of the cartilages of the moveable articulations; but I
believe that it depends wholly upon the laws of osseous nutrition.
Nature limits there the exhalation of the phosphate of lime, as it
limits at the origin of a tendon the exhalation of the fibrin of the
muscle which corresponds to it; it is because the mode of organic
sensibility changes and the vessels of the cartilages are no longer
in relation with the red part of the blood nor with the calcareous
substance. In fact, by supposing the preceding hypothesis true, why do
the cartilages of the immoveable articulations exist? Why should the
motion which elsewhere favours exhalations and secretions, prevent here
the first of these? Why do preternatural ossifications take place in
the most moveable parts, of which the arteries furnish us an example?
Why, in many anchyloses in which the articular surfaces unite, and in
which the motion is destroyed, do not the cartilages disappear?

The cartilages of the cavities have a mode of origin, development and
nutrition, perfectly analogous to that of the articular cartilages.
I would observe that their texture differs, as well as the texture
of these, from that of the cartilages of ossification, in this, that
these last are crossed by many grey lines, and the others are not.
When we cut the cartilages of ossification in any direction whatever,
their divided surfaces exhibit numerous small points which are the cut
extremities of these lines, which appear to be vessels, that, without
yet circulating blood, contain a fluid of a deeper colour than that of
the cartilaginous texture.


II. _State of the Cartilaginous System in the after ages._

As we advance in age, the cartilages become harder, stronger, and less
elastic. The gelatine that nourishes them has a peculiar character;
for we know that the glue made from young animals differs essentially
from that made from old ones. The cooks know very well the difference
there is between the foot of a calf and that of an ox for jelly. This
difference in the substance which essentially composes the cartilages,
and which is undoubtedly their nutritive matter, evidently indicates
that it does not always remain in these organs, but that it is
constantly exhaled and absorbed there, as the phosphate of lime is in
the bones, the fibrin in the muscles, &c.

In the last years of life, ossification seizes upon all the cartilages;
but it begins in an opposite manner in those of the cavities and in
those of the articulations. In the first it is by the centre, in the
second it is by their surface which corresponds to the bone, that it
commences; in general it is much slower in the latter, and among these,
it is slower in the moveable articulations than in the immoveable.

The cartilages of the larynx and the ribs are osseous in their centre
at the age of thirty-six or forty years, and even before; they
afterwards become more and more so; it is this that renders the section
of the thyroid cartilage very difficult in the last periods of life.

In the great number of operations that I have shown to students,
I have satisfied myself, that after sixty years, the bistoury of
ordinary temper is almost always insufficient to make this section;
it requires something much stronger. It is the ossification of the
costal cartilages, which renders old people unable to make those great
efforts of inspiration so common to young ones; with them the diaphragm
especially acts. I attribute also to this early ossification of the
cartilages of the cavities, an ossification which always accompanies
the development of the vascular system, the greater frequency of caries
in this sort of cartilages than in all the others. I know not why
in the larynx the arytenoid cartilages are the most exposed to this
affection; but in the opening of dead bodies, it is a constant fact,
all the cases of laryngeal phthisis with caries, that I have observed
in the dead body, have shown me this.


III. _Preternatural Development of the Cartilaginous System._

The cartilaginous system, like the osseous, is often developed
in organs to which it is naturally a stranger. But there is this
difference, that this phenomenon appears to be an effect of age
in the first, whereas in the second it is always the effect of
disease. Nothing is more common than to find cartilaginous balls in
scirrhous, cancerous tumours, &c.; in the middle of those frequent
morbid productions, in which the parts have an appearance like
lard, in the lungs, liver, &c. when enlarged. I do not know why the
peculiar membrane of the spleen has a great tendency to be encrusted
with gelatine; it is perhaps of all the organs, that in which the
preternatural cartilages are the most frequent. It is usually by
irregular scales that the cartilaginous development appears; sometimes
it attacks the whole membrane, which then presents a convex surface
analogous to the convex surfaces of the moveable articulations, which
the peritoneum covers, as these are covered by the synovial membrane.
Can the spleen, when thus cartilaginous externally, yield to the
changes of size that it often undergoes? I know not.

We know that there are often moveable and loose cartilaginous
substances in the articulations. Do they arise from the ossification
of a portion of the synovial membrane? I presume they do; for we
frequently see them hold to the cartilage by membranous expansions. I
have seen in a dead body, within the last year, the portion of synovial
membrane that goes from the fatty substance behind the patella, to the
depression that separates the condyles of the femur, almost wholly
cartilaginous. If during life it had been detached by the effect of
the motions, it would have formed one of these moveable and loose
cartilages. Besides, as I know but this fact which seems peculiarly
applicable to this point, I can only offer conjectures, especially as
we know that the synovial and serous membranes are of the same nature,
and yet these last hardly ever become cartilaginous.

Moreover these productions follow entirely the ordinary progress
of ossification. At first cartilaginous and without blood vessels,
they soon acquire a red centre, then osseous, which extends from
the centre to the circumference, and which sometimes terminates by
seizing upon the whole cartilage; so that they are real bones. This
last circumstance is however very rare. The state in which we most
commonly find these productions, is that in which they are osseous in
the middle, and cartilaginous at the circumference. I found one of them
in the articulation of the pisiform bone, of the size of the head of a
great pin, and which, in its whole thickness was harder than ivory.



FIBROUS SYSTEM.


The fibrous organs have not been considered by anatomists in a general
manner; no one has yet made a system of them. Separately described with
the parts in which they are found, they cannot, in the present state of
science, present us any of those great views, so useful to the practice
of medicine, which show us each organic apparatus resulting from the
combination of different systems, to which analogous ones are found
in the other apparatus; so that though very different as it respects
their functions, these apparatus are yet subject to the same diseases,
because similar systems enter into their structure.

I presented, two years since, various general views upon the fibrous
membranes, which have opened the way; but these membranes are only a
division of the fibrous system, which must be considered here more at
length.


ARTICLE FIRST.

OF THE FORMS AND DIVISIONS OF THE FIBROUS SYSTEM.

Though all the fibrous organs have precisely the same nature, and
though the same fibre enters into the composition of all, yet the
forms which they assume are extremely various; it is this variety of
form, joined to that of their position and their functions, which has
given them a different denomination, and made us designate them by the
name of tendons, aponeuroses, ligaments, &c.; for there is no general
denomination for the whole system, no word which answers for example
to that of muscle, nerve, &c. which in the muscular, nervous systems,
&c. gives an idea of the organization, whatever may be the form of the
organ. I shall not create a word, I shall be easily understood without
it.

All the fibrous forms can be referred to two general ones; one of these
is membranous, the other in fasciæ. The organ is broad and thin in the
first; it is longer and thicker in the second. Thus the muscles, the
nerves, the bones themselves exhibit alternately this arrangement in
their conformation, as we see in the retina compared with the round
nerves, in the muscular layers of the stomach and the intestines,
compared with the muscles of locomotion, and in the bones of the
cranium compared with those of the extremities.


I. _Of the Fibrous Organs of a Membranous Form._

The fibrous organs arranged as membranes are, 1st, the fibrous
membranes, properly so called; 2d, the fibrous capsules; 3d, the
tendinous sheaths; 4th, the aponeuroses.

1st. The fibrous membranes comprehend the periosteum, the dura-mater,
the sclerotica, the albuginea, the peculiar membranes of the kidney,
the spleen, &c. &c. They are in general destined to form the covering
of certain organs, into the structure of which they enter.

2d. The fibrous capsules, very distinct, as we shall see, from the
synovial surfaces, are a kind of cylindrical sacs, which are found
around certain articulations, especially those of the humerus and
the femur, whose connexions with the scapula and the ilium they
strengthen, by embracing with their two extremities, both surfaces of
the articulation.

3d. The fibrous sheaths are destined to confine the tendons in their
passage upon the bones, where they are reflected, and generally
wherever by muscular contraction they would be made to deviate and
consequently transmit with difficulty to the bones the motion they
receive from the muscles. They may be divided into two kinds; one
receives and transmits the tendons of many muscles united, as is seen
at the wrist, the instep, &c.; the other, like that of the fingers, is
destined for a single tendon, or two only.

4th. The aponeuroses are a kind of fibrous nets more or less broad,
entering always into the system of locomotion, and so arranged that
they sometimes form coverings for different parts, and sometimes
furnish the muscles with points of insertion. Hence the aponeuroses of
covering and the aponeuroses of insertion; each of them is divided into
species.

The aponeuroses of covering are placed sometimes around a muscle, to
which they serve as a general sheath, as we see on the thigh, the
fore-arm, &c.; sometimes upon certain muscles which they partially
retain in their respective places, as that which goes from the
posterior and superior serratus minor to the anterior and inferior, as
the abdominal aponeurosis, as that situated anteriorly to the solæus,
behind the deep muscles of the leg, &c.

The aponeuroses of insertion are sometimes with surfaces more or less
broad, as in the attachments of the triceps femoris, the rectus, the
biceps, &c.; sometimes with fibres separate from each other, and
giving attachment by each of these fibres to a fleshy fibre, as at
the superior insertion of the iliacus, of the anterior tibialis, &c.;
sometimes finally in the form of an arch, and then at the same time
that they give the muscles points of insertion, they allow vessels to
pass under them, as in the diaphragm, the solæus, &c.


II. _Of the Fibrous Organs in the form of Fasciæ._

The fibrous organs arranged in fasciæ are, 1st, the tendons; 2d, the
ligaments.

1st. The tendons are found at the origin, insertion or middle of the
muscles. They are either simple, in the form of elongated cords, as in
the peronæus, the tibialis, and almost all the muscles, or compound, as
in the rectus, the flexors, &c.

2d. The ligaments strengthen the osseous or cartilaginous
articulations, around which they are found. They have regular fasciæ,
as the lateral ligaments of the elbow, the knee, the jaw, &c.; or
irregular fasciæ, as those of the pelvis.


III. _Table of the Fibrous System._

We can in the following table present at a single view the
classification of the fibrous organs that I have just pointed out.

          ┌                ┌Fibrous Membranes.
          │                │Fibrous Capsules.
          │                │                  ┌Partial.
          │Of a membranous │Fibrous Sheaths.  └General.
          │   form.        │                          ┌Partial.
          │                │            ┌For covering └General.
  FIBROUS │                │Aponeuroses │
  ORGANS. │                │            │            ┌With a broad surface.
          │                └            └Of Insertion│In an arch.
          │                                          └With separate fibres.
          │
          │                ┌Tendons     ┌Simple.
          │In the form     │            └Compound.
          │  of fasciæ.    └Ligaments   ┌With regular fasciæ.
          └                             └With irregular fasciæ.

Though the numerous organs which enter into this classification, belong
to very different apparatus, though they seem to be spread here and
there in the economy, without holding together at all, and though all
appear insulated, yet they are almost all continuous and connected; so
that we may consider the fibrous system, like the vascular and cerebral
nervous systems, that is to say, as having a common centre, from which
all the different organs go that form its divisions.

This common centre of the fibrous system appears to me to be the
periosteum, not that I pretend that like the heart or the brain, it
sends out radiations upon the organs that go from it, but because
anatomical inspection shows us that all the fibrous organs are
intimately connected with it, and by its means communicate with each
other; the following observations are a proof of this.

1st. Among the fibrous membranes, that of the corpus cavernosum
intermixes with the periosteum below the ischium; the dura-mater is
continued with it through the foramina at the base of the brain;
by uniting itself by the lamina which accompanies the optic nerve
to the sclerotica, it joins to it this membrane, and thus serves
as an intermediate organ for them. 2d. All the fibrous capsules
above and below the articulation intermix with the periosteum. 3d.
Wherever fibrous sheaths exist their fibres intermix with those
of the periosteum. 4th. All the aponeuroses either of covering or
insertion have a similar intermixing. 5th. Wherever the tendons are
expanded, they are also confounded with this membrane. 6th. At the
two extremities of the ligaments it unites also its fibres to theirs.
There are none scarcely except the albuginea, the perichondrium of
the larynx, the membranes of the spleen and the kidney, that form an
exception to this general rule.

The fibrous system should be considered then in a general manner, that
is to say, as extending itself everywhere, belonging at the same time
to many organic apparatus, distinct in each by its form, but continuous
in the greatest number, having everywhere communications. This manner
of describing it will appear still more natural, if we consider that
the periosteum, the general boundary of the different portions of this
system, is itself everywhere continuous, and at the place where the
articulations divide it, the fibrous capsules and the ligaments serve,
as we have said, to reunite it.

We understand from this use of the periosteum in relation to the
fibrous system, what the advantage is of its situation upon the bones
which offer it a solid support, and give the same also to the organs of
which it is the boundary.


ARTICLE SECOND.

ORGANIZATION OF THE FIBROUS SYSTEM.

In the midst of the varieties of form that we have just examined, the
general organization of the fibrous organs is always nearly the same.
I shall now consider this organization; I shall treat elsewhere of the
varieties it experiences in each part. It arises from the union of a
peculiar texture and of the vascular, cellular systems, &c.


I. _Of the Texture peculiar to the Organization of the Fibrous System._

Every fibrous organ has for a base a fibre of a peculiar nature;
hard, but slightly elastic, insensible, scarcely at all contractile,
sometimes in juxta-position and parallel to each other, as in the
tendons and the ligaments, sometimes crossed in various directions, as
in the membranes, the capsules, the fibrous sheaths, &c. but everywhere
the same, everywhere of a white or greyish colour, and of a remarkable
resistance.

This resistance of the fibrous texture enables all the organs that it
composes to support the greatest efforts. Thus these organs are all
destined to uses which require this faculty in them. The ligaments
forcibly retain the articular surfaces in their proper relation. The
aponeuroses confine the muscles and oppose their displacement. The
tendons constantly exposed to the contraction of these organs, are at
every instant placed between the strong power that they represent and
the more or less considerable resistance situated at the extremity of
the muscles, &c. Such is this resistance, that it is often greater than
that of the bones themselves. We know that by muscular efforts alone,
the patella, the olecranon process and the os calcis are sometimes
broken; now this could not happen, if the extensor tendons, which
corresponded to these different bones, were of a texture that could be
more easily torn.

It is to this resistance that must be attributed the following
phenomena: 1st. We experience the greatest difficulties in making
luxations in the dead body, principally in the articulations called
enarthrodial. 2d. In the living subject the external efforts are rarely
sufficient to produce them; it is necessary that the powerful action of
the muscles should be added. 3d. The punishment formerly employed, of
drawing the limbs of criminals by attaching horses to them, was much
more terrible, because the resistance of the ligaments made it continue
longer; almost always the horses were unable to produce the separation
of the extremities; it was necessary that a cutting instrument should
assist their efforts. 4th. Weights suspended to a tendon do not break
it unless they are enormous; thus the best strings to be employed in
the arts would be these textures of the fibrous organs, if drying did
not take from these organs their softness and flexibility, if moisture
did not alter them, &c. 5th. We cannot without great efforts tear an
aponeurosis, especially those of any thickness, as the fascia lata, the
albuginea, the dura-mater, &c.

Yet this resistance is sometimes overcome in the living body, and we
sometimes see the rupture of the tendons of the solæus, of the small
plantaris, of the extensors of the thigh, &c. How does it happen, that
the softer texture of the muscle never yields, whilst that of the
tendon much more compact is broken? It is because in these cases the
fleshy fibres are always in contraction; consequently far from being
stretched, as the tendinous fibres are which are then found, if we may
so say, passive, their different portions make an effort to approximate
each other; and they do in fact approximate; this gives to the muscle a
density and hardness equal, and in some cases even much greater, than
those of their tendon, as we can ascertain by applying the hand upon a
muscle in contraction. A proof that this kind of ruptures is owing to
the cause I have mentioned, is this, that if in a dead body we suspend
a weight to a muscle detached from the bone at one of its extremities,
it will be the fleshy and not the tendinous portion that will break.

The fibrous texture has been considered by some anatomists, as being
of a nature approaching that of the muscular texture, and even as
being sometimes the continuation of it. Thus they have said that the
tendon was formed only by an approximation of the fleshy fibres,
which, without changing their nature, only lose their redness. Thus
the aponeuroses of covering have been described as an effect of the
pressure of the surrounding bodies upon the most external fleshy
fibres. In order to see how little foundation there is for this
opinion, it is sufficient to observe, 1st, that the dura-mater, the
sclerotica, the periosteum, the ligaments, are evidently of the same
nature as the tendons and the aponeuroses, and that yet they differ
wholly from the muscular texture; 2d, that the chemical composition,
the vital properties, the apparent texture, are entirely different in
the tendinous and muscular fibre; 3d, that there is no relation between
their functions. There is certainly less analogy between the muscle and
the tendon which receives its insertion, than between that and the bone
which furnishes an attachment to it, and whose cartilaginous portion
approximates it in its nature. A muscle and its tendon form an organic
apparatus and not a simple organ.

What is the nature of the fibrous texture? We know not, because we do
not know any of its properties that are characteristic; it has only the
negative ones of those of the muscular texture which is distinguished
by contractility, and of those of the nervous texture which is
characterized by sensibility. We always see it in a passive state; it
obeys the action that is imparted to it, and has scarcely any of its
own.

It establishes a great difference between the organs in which it
exists and the skin, the cellular texture, the cartilages, the serous
membranes, &c.; thus it was wrong to refer all these parts to one and
the same class designated by the name of the white organs, a vague term
that is only founded upon external appearances, upon the approximation
of analyses yet incomplete, and not upon the texture, the vital
properties, the life and the functions of the organs. Fourcroy foresaw
that this extremely general division would be abandoned after further
experiments.

However this may be, the following are the results which the fibrous
texture gives when subjected to maceration, ebullition, drying, the
action of the acids, &c.

Exposed to maceration in a moderate temperature, the fibrous texture
remains a long time without undergoing any alteration; it preserves
its size, form and density; gradually this last diminishes; the texture
softens; but it does not dilate and swell up; its fibres can then be
separated from each other; we see distinctly between them the cellular
texture that unites them. Finally at the end of a very long time,
they become changed into a soft, whitish pulp, which appears to be
homogeneous. All the fibrous organs do not soften equally quick in this
way. The tendons are the first to yield to maceration. Then come the
aponeuroses; among these, those which are formed by the expansion of a
tendon, soften quicker than those destined to cover the limbs, as the
fascia lata, for example. The fibrous membranes, the capsules and the
sheaths of the same nature are more resisting. Finally the ligaments
yield the slowest to the action of water which tends to soften
them; yet when they come originally from a tendon, as the inferior
ligament of the patella, they are more easily macerated. I have made
comparatively, experiments upon all these organs; they give the results
that I have stated.

Every fibrous organ plunged into boiling water, or exposed to great
heat, crisps and contracts like most of the other animal textures; it
diminishes in size, hence it is more solid; it becomes elastic which
it is not in the natural state, and afterwards it ceases to be so when
it becomes softer before passing into the gelatinous state. By placing
all the parts of this system at the same time in water which is made
gradually to boil, we see that this softening comes upon all at the
same degree, and with nearly the same force. This force, which tends
then to make the fibres of this system contract is very considerable;
it is sufficient to break at the place of their attachments, those of
the periosteum which it raises, by this mechanism, from all the bones
that have been boiled for a length of time; to detach the interosseous
ligaments, the obturator membrane, &c. when we plunge them into
boiling water, with the bones to which they adhere; to contract so
strongly the articular surfaces against each other, that they cannot be
moved, when, surrounded with their ligaments, they have been exposed to
the concentrated action of caloric.

The fibrous texture gradually softens in water, becomes yellowish,
semi-transparent and finally melts in part. By boiling together all the
parts of the fibrous system, I have observed that the tendons soften
first, then the aponeuroses, then the membranes, fibrous capsules and
sheaths, and finally the ligaments, which are, as in maceration, those
that yield last. Many have already made this remark, to which I add
that all do not yield equally. Those placed between the layers of the
vertebræ are the most tenacious; they do not take that yellow colour,
that semi-transparency, common to all the fibrous system when boiled;
they remain white and tough; they appear to contain much less gelatine,
and to be entirely different in their nature.

Exposed to the action of the air, the fibrous system loses its
whiteness by the evaporation of the fluids it contains; it acquires
the horny hardening, becomes yellow, in part transparent and breaks
with facility. Some days after having been dried, if replunged into
water, it becomes nearly as white and soft as it was before; so that
we can truly say, that its white colour is owing to water alone; this
phenomenon takes place especially in the tendons. I have observed also
in these last another remarkable phenomenon; it is that when they have
macerated for some time, and are afterwards dried, they do not become
yellow in drying, but remain of a very decided white. Without doubt the
whole fibrous system would do the same.

The action of sulphuric and nitric acids quickly softens the fibrous
texture, and reduces it to a kind of pulp, blackish in one and
yellowish in the other; at the instant we plunge this texture into the
acid, it crisps and contracts as in boiling water.

The fibrous texture resists in general putrefaction less than the
cartilaginous; but it yields to it more slowly than the medullary,
the cutaneous, the mucous, &c. In the midst of these putrid and
disorganized textures in the subjects in our dissecting rooms, we find
this still untouched; it finally becomes changed also. Water in which
it has been macerated gives an odour less offensive than that which has
been used for the maceration of most of the other systems.

More digestible than the cartilages and the fibro-cartilages, the
fibrous texture is less so than most of the others. The experiments
of Spallanzani and Gosse prove this. It appears that it yields to the
action of the digestive juices in the same order as to maceration,
ebullition, &c.; that is, 1st, the tendons; 2d, the aponeuroses; 3d,
the different fibrous membranes; 4th, the ligaments, which are the
most indigestible. I would observe however that when boiling has once
softened the fibrous texture, it is all digested nearly alike. Thus
the cartilages are as easy, and even more so, of digestion, than the
tendons, when they have become gelatinous, as Spallanzani proved upon
himself, though when raw they are much more indigestible.


II. _Of the Common Parts which enter into the Organization of the
Fibrous System._

The cellular texture exists in all the fibrous organs; but it is more
or less abundant according as the fibres are more or less distant. In
certain ligaments, it forms for the fibrous fasciæ, sheaths analogous
to those of the muscles; in others, in the tendons, the aponeuroses,
&c. we hardly perceive it; but everywhere it becomes very evident by
maceration, by morbid affections, as, for example, by the fungi of
the dura-mater, by the carcinoma of the testicle, which has seized the
albuginea, by certain swellings of the periosteum, &c. In all these
cases the fibrous texture relaxed, softened, preternatural, and of a
spongy nature permits its fibres to separate and the cellular organ to
appear. The development of fleshy granulations, the soft nature which
these granulations have in certain wounds in which the fibrous organ is
concerned, prove also the existence of the cellular organ there, which
is in general in small quantity; this does not contribute a little to
produce the resistance and the force of the organs that belong to it.
Does this cellular texture contain fat? At first view we can hardly
observe it, since we can scarcely distinguish this texture. Yet I have
many times observed that by submitting to desiccation portions of
aponeuroses, periosteum, dura-mater, &c. entirely stripped of every
foreign part, when all these fluids had evaporated, and the organ had
the appearance of parchment, a fatty exudation remaining on many places
on its surface.

The existence of vessels varies in the fibrous system; much developed
in some organs, as in the dura-mater, the periosteum, &c. they are
less so in others, as the aponeuroses, and not at all in some, as
the tendons. I would observe in general that it is in those in which
they are the most evident, that inflammations and the different kinds
of tumours are the most frequently observed. The affections of the
dura-mater, the periosteum, &c. compared with those of the tendons, are
a remarkable proof of this.

I do not know that absorbent vessels have been traced in the fibrous
system.

The nerves appear to be equally foreign to it, notwithstanding what has
been written on those of the periosteum, the dura-mater, &c. &c.


ARTICLE THIRD.

PROPERTIES OF THE FIBROUS SYSTEM.


I. _Physical Properties._

The fibrous system has but a slight degree of elasticity in the natural
state; but when its different organs are taken from the body and dried,
they acquire it very considerably; thus the tendons, the aponeurotic
expansions, &c. which in a fresh state would be incapable of any
vibration, are found to resound in instruments when they are very dry.


II. _Properties of Texture._

The properties of texture are evident in the fibrous system, but they
are less so than in many others.

Extensibility is seen in the dura-mater, in hydrocephalus, in the
periosteum; in the different enlargements of which the bones are
susceptible; in the aponeuroses, in the swelling of the extremities,
and the distension of the abdominal parietes, which, as we know, are
aponeurotic as well as fleshy; in the fibrous capsules, in articular
dropsies; in the tunica sclerotica and albuginea in the swelling of
their respective organs.

This extensibility of the fibrous system is subjected to an uniform
law, which is unknown to the extensibility of most of the other
systems; it can only take place in a slow, gradual and insensible
manner. Thus when it is too quickly put into action, two different
phenomena take place, which equally suppose the impossibility of its
extending suddenly, as for example, a muscle, the skin, the cellular
texture, &c. do. 1st. If the fibrous organ makes a resistance greater
than the effort which it experiences, then it does not yield, and
different accidents result from it. We have many examples of this,
in the inflammatory swellings that appear under the aponeuroses of
the limbs, under those of the cranium, within the fibrous sheaths of
the tendons, &c. Then these fibrous organs not being able to stretch
with the same rapidity as the subjacent parts which swell, compress
painfully these swollen parts, and sometimes even expose them to
gangrene; this is what takes place in those strangulations so frequent
in surgical practice, and which require different operations to relieve
them. 2d. If the fibrous organ is inferior in its resistance to the
sudden effort which it experiences, it breaks instead of yielding;
hence the rupture of the tendons, the tearing of the fibrous capsules
and of the ligaments in luxations, that of the aponeuroses in certain
very rare cases reported by different authors, &c. &c. We easily
understand that the great resistance with which the fibrous texture is
endowed, is principally owing to the impossibility of yielding suddenly
to the impulse that is given to it.

In the slow and gradual extension of the fibrous organs, we observe
that often instead of becoming thinner and enlarging at the expense of
their thickness, they increase, on the contrary, in this dimension.
The albuginea of a scirrhous testicle, the sclerotica of a dropsical
or cancerous eye, the periosteum of a ricketty bone, &c. show us this
phenomenon, the reverse of which is sometimes observed, as in the
distensions of the abdominal aponeuroses produced by pregnancy, by
ascites, and also in hydrocephalus, &c.

The contractility of texture is accommodated in the fibrous system, to
the degree of its extensibility; as it cannot suddenly be distended,
it cannot suddenly contract when it ceases to be distended. This
fact is remarkable in the division of a tendon, of a portion of
aponeurosis, of a ligament laid bare in a living animal, in an
incision of the dura-mater, to discharge blood effused under it, &c. In
all these cases, the edges of the division undergo a separation hardly
perceptible; thus in the rupture of the tendons, the separation being
produced, not by the contraction of the divided extremities, but only
by the motions of the limb, the contact is effected by the position
in which in the natural state this tendon is not drawn: whilst in a
divided muscle, not only this position is necessary, but that in which
there is the greatest possible relaxation, and yet oftentimes contact
is not effected. If whilst a muscle is stretched, we cut its tendon
in a living animal, the end attached to the fleshy fibres separates a
little from the other by the retraction of these fibres; but that which
is attached to the bone remains immoveable, so that there is then but
one cause of separation to this, whereas there are two in a divided
fleshy part. If we cut a tendon when the muscle is relaxed, its ends
remain in place.

The contractility of texture is evident, however, at the end of some
time, in the fibrous system, especially when the organ has been first
stretched; for, when it is divided in its natural state, it is always
hardly any thing. The sclerotica after the puncture of the eye, or
after the amputation of the anterior half of this organ, and the
evacuation of its humours, the tunica albuginea, the peculiar coat of
the spleen and that of the kidney, after the resolution of a tumour
that had stretched their respective organs, the fibrous capsules
after the discharge of the fluid of articular dropsies, the abdominal
aponeuroses after the first and even the second accouchement, the
periosteum after the resolution of exostoses, &c. gradually contract
and resume their original forms.


III. _Vital Properties._

There is never in the fibrous system animal contractility, nor sensible
organic contractility. Organic sensibility and insensible organic
contractility are found there as in all the other organs.

The animal sensibility exists in it in the natural state; but it
appears in a peculiar way, of which no system in the economy, I
believe, offers an example and which no one has precisely pointed
out. The ordinary agents that put it in action, such as the different
stimulants, mechanical, chemical, &c. cannot develop it here, unless
the organ is in an inflammatory state. The tendons, the aponeuroses,
the fibrous membranes, the ligaments, &c. laid bare in operations,
in experiments upon living animals and irritated in various ways do
not occasion any pain. What has been written on the sensibility of
the periosteum, the dura-mater, &c. taken in this sense is evidently
contrary to observation. But if the fibrous organs are exposed to a
sudden and violent extension, then the animal sensibility is evident in
it to the greatest degree; this fact is particularly remarkable in the
ligaments, the fibrous capsules, the aponeuroses, &c.

Lay bare an articulation in a dog, that of the leg, for example;
dissect carefully the organs that surround it; remove the nerves
especially, so as to leave nothing but the ligaments; irritate these
with a chemical or mechanical agent; the animal remains unmoved and
gives no sign of pain. Then stretch these ligaments, by twisting
the articulation, the animal in an instant throws himself down, is
convulsed, cries out, &c. Finally cut these ligaments so as to leave
only the synovial membrane which exists here without the fibrous
capsule, and twist these two bones in an opposite direction; the
twisting ceases to be painful. The aponeuroses, the tendons even laid
bare and drawn in an opposite direction, produce the same phenomenon.
I have frequently repeated these experiments which prove incontestably
what I have advanced, viz. that the animal sensibility of the fibrous
system, incapable of being brought into action by the ordinary means,
is very evident in the distensions of which they are the seat. Observe
that this manner of being excited is analogous to the functions that it
performs. Separated in fact by its deep position from every external
excitement which can act upon it chemically or mechanically, it has no
need, like the cutaneous system for example, of a sensibility which
would transmit the impression of it; on the contrary, the most of
these organs, as the ligaments, the fibrous capsules, the tendons,
&c. being very subject to being distended, stretched and twisted in
the violent motions of the limbs, it was necessary that they should
communicate to the brain this kind of irritation, the excess of which
might without this become injurious to the articulations or the limbs.
Observe how nature accommodates the animal sensibility of each organ to
the different excitements it may experience, to those especially which
would become dangerous if the mind was not informed of them; for this
vital power is the essential agent by which the animal watches over its
preservation.

It is to this sort of sensibility of the fibrous system that must be
principally attributed, 1st, the acute pains that attend the production
of luxations; 2d, those more severe ones which patients experience in
the extensions necessary to reduce them, especially when, as in those
of long standing, we are obliged to employ considerable force; 3d,
the intolerable suffering of the punishment that consisted in drawing
a criminal with four horses; 4th, the painful sensation which arises
from twisting, which is occasioned by a stretching of the spinal column
and consequently of its ligaments, by turning the head too quickly,
&c.; 5th, the acute pain that those experience immediately before the
accident who break a tendon, a pain which ceases in part when the
rupture takes place; 6th, that less sensible pain which we feel when
any tendon, the tendo Achillis for example, is from a bad position too
much stretched; 7th, the great increase of pain that is experienced,
when a swelling exists under an aponeurosis, which being unable to
yield, is very powerfully raised; 8th, the painful sensation we feel
in the ham when we wish to force the extension of the leg, by which we
stretch the two oblique ligaments destined to confine this extension,
&c. &c.

It is without doubt to the insensibility of the fibrous organs to
one kind of excitement, and their sensibility to another, that must
be referred the contradictory results of the experiments of Haller
on the one part, and those of his antagonists on the other, upon the
dura-mater.


_Character of the Vital Properties._

The vital activity is much greater in the fibrous, than in the osseous
and cartilaginous systems. This is proved very evidently, 1st, by the
degree of animal sensibility which we have just observed in it, and
which is foreign to the other two systems; 2d, by the much greater
disposition of this system to become the seat of pains more or less
frequent, and especially of inflammation, &c.; 3d, by the much more
acute character that this affection has in it, as we see in acute
rheumatism, which principally affects the fibrous parts of the great
articulations of the axilla, the hip, the knee, the elbow, &c. the
aponeurotic part of muscles, &c.; 4th, moreover, by the great mobility
of rheumatic pains, which go with astonishing quickness from one
place to another, which consequently suppose a great quickness in the
alteration of the vital forces of the different parts of this system;
5th, by the greater rapidity of its cicatrization; thus by laying
bare fractures made for the purpose in animals, I have constantly
observed that the fleshy granulations coming from the periosteum and
the medullary organ, are all formed, whilst those furnished by the
bone itself have hardly commenced. I would observe in regard to this
cicatrization, that the parts of the fibrous system in which the
greatest number of blood vessels enter, as the periosteum, the fibrous
membranes, the capsules, &c. are the most capable of this phenomenon,
which takes place with much more difficulty in those where little or
scarcely any blood goes, as in the tendons, the ends of which are very
slow in uniting; 6th, we may finally be convinced of the difference
of vitality of the fibrous system and that of the preceding ones, by
the progress of an exostosis compared with that of periostosis, or a
swelling of the dura-mater, &c. Yet there is still in respect to the
vitality a remarkable slowness in this system. We see it especially in
certain affections of the limbs, in which gangrene takes place, and
makes, like the inflammation that precedes it, rapid progress in the
cellular texture, the muscles, &c. whilst that, as I have said, the
tendons that have been laid bare do not alter until some time after,
and are remarkable for their whiteness in the midst of the general
blackness or lividity.

The fibrous system presents a remarkable phenomenon; it is that it
hardly ever contributes to the formation of pus. I do not know that
after inflammations of this system, purulent collections have been ever
observed. Rheumatism, which is ranked with the phlegmasiæ, is never
accompanied by these collections; some gelatinous extravasations only
have been found around the tendons. That which was formerly taken for a
suppuration of the dura-mater in wounds of the head, is very evidently
a purulent oozing from the arachnoides, analogous to that of all the
other serous membranes. Why does this system refuse, or produce pus
with so much difficulty, or why is it not as much disposed to do it
as most of the other systems? I know not. Nor do I know that in the
midst of the cartilages collections of this fluid have been found. The
inflammations of the cartilaginous system are remarkable, because they
rarely or never terminate by suppuration.


_Sympathies._

All the kinds of sympathies are observed in the fibrous system. Among
the animal sympathies, the following are some of sensibility. 1st. In
certain periostoses which occupy but a small surface, the whole of the
periosteum of the bone that remains sound, becomes painful. 2d. After
a puncture, or bruise of the periosteum, the whole of the limb often
swells and becomes painful. 3d. In the affections of the dura-mater,
the eye is frequently affected, and cannot bear the light, a phenomenon
which may also depend on the communication of the cellular texture, but
which is certainly sometimes sympathetic. 4th. When we make extension
to reduce a luxation, and the articular ligaments consequently suffer
much, the patient often complains of pain in a very distant part of the
limb, &c.

Contractility is also brought into action in the animal sympathies of
the fibrous system. 1st. The puncture of the centre of the diaphragm
causes, it is said, in the facial muscles, a contraction which produces
a sardonic smile. 2d. The injury of the aponeuroses, the stretching
of the ligaments in the luxations of the foot and the tearing of the
tendons, are frequently accompanied by convulsive motions of the jaws
and even well marked tetanus. 3d. A splinter fixed in the dura-mater
produces contractions in the different muscles of the economy. 4th.
In injuries of the albuginea and the external aponeuroses, we often
observe similar phenomena.

In the organic sympathies of the fibrous system, it is sometimes
the insensible organic contractility that is brought into action,
and sometimes the sensible organic contractility; the following
are examples of the first. 1st. The dura-mater being inflamed, the
inflammation which always supposes an increase of the tonic forces
or of the insensible organic contractility, is often discoverable in
the pericranium and vice versa. 2d. The irritation of a considerable
extent of the periosteum often makes the medullary organ inflame and
suppurate. 3d. The articular ligaments being stretched by twisting,
all the neighbouring parts, and frequently the whole limb, swell and
become a centre of irritation in which all the vital forces of life,
insensible contractility in particular, are found much more raised than
usual, &c.

At other times it is the sensible organic contractility which is
brought into action. 1st. We often observe in the operation for
cataract by depression, that the wound of the sclerotica occasions
sympathetic vomitings, risings of the stomach, intestines, &c. 2d.
A violent pain in any part, in the fibrous system in particular,
increases very much the sensible organic contractility of the heart
and thus produces from sympathy an acceleration in the motion which
it gives to the blood. 3d. I have seen a man in whom Desault reduced
a luxation, and who, from the great pain which the stretching of the
ligaments gave him, was unable to retain his fœces, so great was the
contraction of the rectum.

We see that in these sympathies, it is sometimes the fibrous system
which exerts its influence upon the others, and sometimes they exert
their action upon it. It is principally when it is drawn, when the
peculiar kind of animal sensibility which it enjoys is put into action
that it occasions in the whole economy a remarkable sympathetic
derangement. I presume the ancients considered as nerves all the
white parts, the ligaments, the tendons, &c. on account of the very
serious accidents they had observed from their stretching in sprains,
in complicated luxations of the knee, the elbow, the ankle, luxations
which can never be produced without a violent stretching of many
ligaments, of aponeurotic and tendinous parts, &c. A stroke of a sabre
which divides the ligaments of the tarsus, a body which bruises them,
produce consequences much less serious, than a false step that twists
them. This leads us to an important general consideration, the truth
of which is proved by the examination of the other systems; viz. that
it is the predominant vital property in a system, which is especially
brought into action by sympathies. As the animal sensibility, capable
of responding to the agents of distension, is here the most strongly
marked, it is this that performs the principal part in the fibrous
sympathies.


ARTICLE FOURTH.

DEVELOPMENT OF THE FIBROUS SYSTEM.


I. _State of the Fibrous System in the first age._

In the midst of the mucous state of the embryo, we cannot distinguish
the fibrous organs. All is confounded; it is not until many other
organs are formed, that we discover any traces of them. Those in the
form of membranes appear at first like transparent nets; those arranged
in fasciæ seem to be a homogeneous body. In general the fibres are not
distinct in the first age; the aponeuroses, the fibrous membranes,
the tendons, &c. do not exhibit any trace of them; all then seems
to be uniform in the texture of the fibrous organs. In the fœtus of
seven months, we begin to distinguish the white fibres. Few at first,
and distant from each other, they gradually approximate after birth,
are arranged in a parallel manner, or cross in different directions,
according to the organ which they finally possess themselves of
entirely at a certain age. It is especially on the phrenic centre of
the diaphragm, the dura-mater, the aponeurosis of the thigh, that we
easily make these observations.

As the fibres are developed in the fibrous organs, they have more
resistance and hardness. In the fœtus and in the first years, they are
extremely soft and easily yield. Their whiteness has a tinge wholly
different from that of a more advanced age; they are of a pearly white.
It is only gradually that they arrive at that degree of force that
especially characterizes them.

It is to this softness, this want of resistance of the fibrous system
in the first years, that the following phenomena must be attributed.
1st. The articulations yield at this age to motions which the stiffness
of the ligaments afterwards renders impossible; all extensions can
then be carried beyond their natural degree. We know that it is at
this period that tumblers begin to practice; they would never be able
to execute those extraordinary motions, which astonish us, if habit
did not preserve in them from infancy the power of these motions. 2d.
Luxations are in general rare in the first age, because the fibrous
capsules yield and do not break. 3d. Sprains have then less serious
consequences. 4th. The inflammatory swellings under the aponeuroses are
rarely susceptible of those strangulations oftentimes so severe at the
adult age. 5th. This softness of the fibrous system accommodates itself
also in the tendons, the ligaments, the aponeuroses, &c. on the one
hand to the multiplicity and frequency, and on the other to the want of
power of the motions of the infant.

I would remark, that although the fibrous system has in the first age a
softness of texture nearly uniform in all the parts that belong to the
same order, yet it is more or less developed according to the regions
in which it is found. In general, when it belongs to the organs that
are early developed, as to the brain by the dura-mater, to the eyes
by the sclerotica, &c. it has in proportion more size and thickness;
but it is only in its dimensions, and not in its intimate organization,
that these differences then exist.

It is probable that this mode of organization of the fibrous system
has an influence, at the period of which we are treating, upon its
degree of vitality and consequently upon its diseases. We know that
rheumatism, which appears very probably to affect this system, is
rarely the attendant of children of the first age; that in a hundred
patients affected with it, there are ninety at least above the age of
fifteen or sixteen years.

Subjected to ebullition, the fibrous system of the fœtus and the infant
easily melts, but does not take that yellow colour, which it constantly
has, when boiled in the adult age; we know that the jellies made from
young animals are much whiter than those from older ones.


II. _State of the Fibrous System in the after ages._

As we advance in age the fibrous system becomes stronger and more
compact; it remains stationary in the adult age, though the alternate
absorption and exhalation of nutritive substances constantly continue.
These two functions can scarcely be seen in the ordinary state; but the
first is very apparent when from a contusion or any internal cause, the
periosteum, the fibrous capsules, the ligaments, &c. swell. The second
in its turn predominates, when the swelling subsides and resolution
takes place.

In old persons, the fibrous system becomes more and more compact and
contracted; it yields more slowly to maceration and putrefaction. The
teeth of animals that feed upon it, tear it with more difficulty; the
gastric juices act upon it less easily. Spallanzani has observed, that
the tendons and aponeuroses of old animals were much more indigestible
than those of young ones. With age, the force of the fibrous texture
increases; but its softness diminishes; hence the difficulty of the
motions, from its stiffness. The ligaments and the fibrous capsules do
not allow the articular surfaces to separate easily from each other;
the tendons bend with difficulty; when we pass externally on places
where they are directly under the integuments, we perceive that they
are hard, not supple, &c. It requires a long time to soften them by
ebullition. The whole fibrous system becomes yellow. We should say that
it approached then that state in which it is compact, semi-transparent
and has the horny hardening to which desiccation reduces it; so that if
we could suppose this system going through quicker than the others the
different periods of its decrease, all the motions would cease from the
rigidity of the ligaments, tendons and aponeuroses, though the energy
of contraction might still subsist in the muscles.


III. _Preternatural Development of the Fibrous System._

We have seen that different productions belonging, by their nature, to
the osseous or cartilaginous systems, are sometimes preternaturally
developed in certain parts. Morbid anatomy also shows us productions,
in which the fibrous appearance is very evident. I have many times
made this observation in tumours of the womb, the fallopian tubes,
&c. Instead of the lardy matter which is so common in these organic
affections, we see one or several masses of fibres, very distinct,
yellow, &c. I cannot however say that these excrescences belong
essentially, by the substances that compose them, to the fibrous
system, not having made upon them, experiments similar to those which I
have made upon the organs of this system.


ARTICLE FIFTH.

OF THE FIBROUS MEMBRANES IN GENERAL.

After having considered the fibrous system in a general manner, as
it relates to its organization, its life, its properties and its
nutrition, I shall now examine it more particularly in the great
divisions it offers, and which we have pointed out above. I begin with
the fibrous membranes.


I. _Forms of the Fibrous Membranes._

These membranes which comprehend, as has been said, the periosteum, the
dura-mater, the sclerotica, the albuginea, the peculiar membrane of the
spleen, the kidneys, the corpus cavernosum, &c. are almost all destined
to form external coverings, kind of sacs in which are contained the
organs they invest.

These organs are not, like those around which the serous surfaces are
spread, as the stomach, the intestines, the bladder and the lungs,
subject to alternate dilatations and contractions. This would not
accord with their degree of extensibility. They are fitted exactly to
the form of these organs, and have none of those numerous folds which
we see in the serous membranes, if we except however the dura-mater.
Their two surfaces are adherent; a character which distinguishes them
especially from the preceding membranes, as well as from the mucous.

One of these surfaces, intimately united to the organ, appears to send
various elongations into it, which identify at first view its existence
with that of the membrane. Many fibres detached from the albuginea,
from the covering of the corpus cavernosum, from the peculiar tunic
of the spleen, &c. or rather adhering to these tunics, penetrate the
respective organs of these membranes, and crossing there in various
directions, form as it were the outline and frame, around which are
arranged and supported the other constituent parts of these organs,
which seem from this to have the external membranes for a mould; as we
see when these moulds are removed, irregular vegetations shooting up
here and there. The callus, in displacements too great to allow the
periosteum to extend over the divided surfaces, is rough and uneven.
The form of the testicle alters, when the albuginea has been divided at
any part. This adherence of the fibrous membrane which covers different
organs, to the internal elongations of these organs, and the fibres
which compose their outline, has made anatomists believe that the
nature of one was the same as that of the others, that these were but
elongations of the membrane. I thought so when I published my Treatise
on the Membranes; but new experiments have since convinced me of the
contrary.

I am confident that the membrane of the corpora cavernosa belongs to
the fibrous system alone. The internal spongy texture, contained in
the cavity of this membrane, has not the nature of it, is not as all
anatomists say an elongation of it. The spongy texture is not made by
laminæ, which, according to the common expression, are detached from
the membrane and produce it by their interlacing. This is a separate
body, unlike in its life and its properties.

By exposing a corpus cavernosum to ebullition, I have evidently
observed this difference; the external membrane does, like all the
fibrous organs, become thick, yellowish, semi-transparent, then melts
more or less into gelatine; the spongy texture, on the contrary,
remains white, soft, does not increase in size, hardly crisps at all
from the action of fire, exhibits, in a word, an appearance which I can
compare to no texture treated in the same way by ebullition.

Maceration also answers very well to distinguish these two textures.
The first yields but slowly to it; its fibres remain a long time
distinct; they have still their natural arrangement, when the second
is already reduced to a homogeneous, reddish pulp, in which nothing
fibrous, nothing organized can be any longer traced. In general, it
appears that the spongy texture of the corpora cavernosa is their
essential part, that in which the great phenomena of erection take
place, that which animates the peculiar kind of mobility which
distinguishes it from the other organs. The fibrous shell is only
accessory to its functions; it is but a covering; it is only formed to
obey in erection the impulse which is communicated to it.

When we expose the corpus cavernosum to the action of the nitric acid,
the spongy texture, freed from the blood it contained, becomes of
a much deeper yellow than the fibrous membrane; this enables us to
distinguish them clearly from each other.

By exposing the testicle to the action of boiling water, we also
observe that its internal texture assumes an aspect wholly different
from that of its external membrane; it becomes of a deep brown, whilst
the other remains white; it does not assume the gelatinous appearance
in so decided or in so prompt a manner as that of the corpus cavernosum.

Subjected to maceration, the testicle is also wholly different in its
covering and in its internal texture.

The surface of the fibrous membranes, opposite to that which
corresponds to their organ, is joined to the neighbouring parts,
sometimes in a loose manner, as the covering of the corpus cavernosum,
sometimes by very tight bands, as the dura-mater. In general the
membranes, and even all the fibrous organs, have a singular tendency
to unite intimately to the serous and mucous surfaces. We find examples
of this in the serous membranes in the union of the dura-mater with
the arachnoides, of the albuginea with the tunica vaginalis, and the
fibrous capsules with the synovial. Such is the intimacy of this
adhesion, that the most careful dissection cannot destroy it in adult
age. In infancy, it is much less, as we see very well especially in
the relation that exists between the base of the pericardium and
the phrenic centre, a relation which is such, that we can with ease
separate in the first age the two surfaces which are rather contiguous
than continuous, whilst in the after ages we are unable to do it.

As to the union of the mucous surfaces with the fibrous, when they are
found contiguous, they are entirely confounded; this is observed in
the pituitary membrane, in that of the sinuses, of the ear, &c. The
perichondrium of the larynx and of the trachea is only a part of their
internal membrane. In all these parts, the periosteum so intermixes
with the mucous surface, that it is impossible to separate them, and
they are removed together from the bone, which then remains bare. The
vas deferens, the fallopian tubes, the ureters, &c. are also very
evidently fibro-mucous.


II. _Organization of the Fibrous Membranes._

The fibrous membranes have in general a very compact texture, of a
remarkable thickness; they are formed only of a single lamina. The
dura-mater seems to be an exception to this rule, as its folds form
the falciform process and the tentorium cerebelli; but except at the
place of the sinuses, it is difficult and even impossible, to find two
distinct laminæ.

These membranes have more vessels than all the other divisions of the
fibrous system; they are perforated by a great number of foramina for
the passage of these vessels, most of which only pass through them,
and afterwards go to the organs they cover. These foramina, each of
which is larger than the branch it transmits, form also a character
of the fibrous membranes, distinct from the serous, which are always
folded up, and never open to allow the vascular system to penetrate
their respective organs.

The particular description however of the membranes of which we are
treating, will be added to that of the organs they surround. I shall
except the periosteum, whose description belongs to and may be made in
a general way, whether because clothing the whole osseous system, we
cannot consider it separately, or because, as I have said, it is the
centre from which arise and to which go all the organs of the fibrous
system, so that its functions relate still more to this system than to
that of the bones.


III. _Of the Periosteum. Of its Form._

This membrane surrounds all the bones. Hard, resisting, of a grey
colour, it forms for them a covering which extends everywhere, except
where the cartilages cover them. Its thickness is remarkable in
infancy; it is thinner in proportion in the adult and becomes more firm
and compact.

The ancients described it as extending from one bone to another over
the articulation, and thus forming a continuous sac for the whole
skeleton. This idea is incorrect. At the junction of the bones, the
periosteum intermixes with the ligaments which serve it as a means of
communication, and it is in this way only that we can understand its
continuity. The crown of the teeth is destitute of it, as well as all
the osseous productions that grow upon the head of certain animals.

The periosteum is feebly united to the bone in infancy; it can then be
separated with great ease, especially on the middle part of the long
bones. In the adult, as the calcareous substance gradually encrusts its
most internal fibres, the adhesion becomes very strong; it is extreme
in old age, in which this membrane is often reduced to a very delicate
layer by the progress of ossification. The constant pressure exerted
by the muscles in their contractions, can also have a little influence
upon this adhesion. Various elongations pass from the periosteum to the
bone. They are much more numerous at the extremities of the long bones
and upon the short bones, than upon the middle of the long bones, or
the broad ones; which may easily be conceived of, from the much greater
number of foramina in one than the other part. These elongations
accompany the vessels, line the canals which pierce through the bone,
are lost in those which terminate in its substance, do not penetrate
the medullary cavity, and confined to the osseous texture alone,
establish, between it and the membrane from which they arise, immediate
relations.

It is the destruction of these relations, when the periosteum is
diseased or destroyed for a considerable extent, that produces the
death and separation of the bone. There is however this difference
between this phenomenon and the death of the bone by the injury of the
medullary membrane, that if this is disorganized, necrosis seizes upon
the whole bone, whilst if we irritate and tear the periosteum in the
middle part of a long bone, for an extent nearly equal to that of this
medullary membrane, the external laminæ of the compact texture alone
are detached by exfoliation, and the bone remains the same. I have made
this experiment the year past upon two dogs. As to that which consists
in removing the periosteum, not only from the middle part, but from the
whole surface of the bone, I do not know that any one has been able to
try it; it has appeared to me impossible; it might be practicable, but
the animal would soon die from the extent of the injury, and thus we
could have no result from it.

The relations of the periosteum with the neighbouring organs vary
remarkably. In the greatest number of bones, there are muscles that
slide upon it; the cellular texture unites it to them more or less
closely according as the motions are more or less considerable. In
consequence of inflammations, it loses this laxity, and often all
motion ceases.


_Organization of the Periosteum._

The direction of the fibres of the periosteum is nearly analogous to
that of the bones, the long bones especially as well as the short; but
it has not the radiated structure of the flat bones that it covers.
These fibres placed upon each other, have different lengths; the
superficial ones are the longest; those which correspond immediately
with the bone run but a short distance. In general all become very
evident in some diseases of the bones. I recollect among other examples
of the preternatural development of the fibres, a man affected with
elephantiasis, and at the same time a swelling of the compact texture
of the tibia, which was of a remarkable thickness. The periosteum of
this bone was very thick, and adhered so little to the bone, that
the slightest effort was sufficient to raise it in its whole extent,
and its fibres were so distinct, that it might have been taken, when
separated from the bone, for a portion of plantar or palmar aponeurosis.

The periosteum borrows its vessels from those of the neighbouring
parts. Their innumerable branches ramify in it ad infinitum, form there
a net-work, which injections, especially in infants, make very evident,
they are afterwards lost in it, or penetrate the compact texture of the
bone, or return to the neighbouring parts to form anastomoses.

This membrane receives, as we have said, the insertion of almost all
the fibrous system, of the tendons, the ligaments and especially the
aponeuroses. This insertion has no connexion with the bone in infancy;
but ossification soon seizing upon the most internal laminæ, all the
fibrous organs appear to be identified with the bone in the adult. I
would observe that this arrangement coincides with the prodigious power
of drawing that the muscles, having become more developed, often exert
at this age, and which only spent upon the periosteum, as it would have
been without its ossification, would not have found in it a sufficient
resistance, whereas acting also upon the bone, it moves it without
endangering its covering. The general organization, the properties and
the life of the periosteum are the same as those of the fibrous system;
I shall not treat of them.


_Development of the Periosteum._

In the fœtus, this membrane is soft, spongy, containing much gelatinous
fluid; it melts easily in water; its fibres are not distinct; they
become so as we advance in age, and at the same time the softness
diminishes and the resistance increases. The periosteum in old age
has extreme tenacity; it resists ebullition almost as much as the
ligaments; those who prepare skeletons know this very well. It tears in
various places, because its fibres in contracting are detached from the
bone; but what remains becomes with great difficulty gelatinous.


_Functions of the Periosteum._

The periosteum defends the bones which it covers from the impression
of the moveable parts that surround it, from that of the muscles, of
the arteries, whose pulsation would wear them, as happens in certain
aneurismal tumours near the sternum, the vertebræ, &c.

It is a kind of parenchyma of nutrition in reserve, if I may so express
myself, always ready to receive the phosphate of lime, when it cannot
be carried upon the bone that has become diseased; hence natural and
artificial necroses which never take place in the teeth, from the
want of this membrane. These little bones have caries and various
alterations, but not true necrosis.

We cannot doubt that the internal laminæ of the periosteum are
successively ossified, and thus contribute not a little to increase
the bone in thickness, when its increase in length is finished. I
would observe upon this subject, that not only it, but all the fibrous
system, has a singular affinity with the phosphate of lime. Next to
the cartilaginous system, it has the greatest tendency to be encrusted
with it, no doubt because its kind of general vitality, of organic
sensibility in particular, has much analogy with that of the bones.
Where the tendons in sliding upon the bones experience great friction
they become osseous. The dura-mater and the tunica albuginea are very
often ossified; the sclerotica serves as a parenchyma for much earthy
substance in birds, which in consequence have it extremely hard.

The periosteum has no connexion with the formation of the bones; it
is only accessory to that of the callus; it is a kind of limit which
circumscribes within its natural bounds the progress of ossification,
and keeps it from irregular aberrations. Does it prepare the blood
which serves to nourish the bones? This question cannot be settled by
any experiment; but we are sure that the vital properties which it
enjoys, do not enable it to accelerate the circulation of the blood
arriving at the bones, as some authors have thought.

It seems to me moreover that they have described the periosteum too
exclusively in relation to the bones; no doubt it is necessary to these
organs; but perhaps it performs in relation to the fibrous organs a
still more important part. If nature has placed it everywhere on the
osseous system, it is probably in great part, as I have said, because
it finds in this system a general, solid and resisting support, which
enables it to resist the various drawings, that the whole fibrous
system makes upon it, drawings which are sometimes communicated to this
last system. This is a new point of view in which the periosteum should
be described, and it will yield much more to general considerations,
than that in which Duhamel, Fougeroux, &c. have considered this
membrane.


IV. _Perichondrium._

We find on all the non-articular cartilages a membrane exactly
analogous to the periosteum, and which is called perichondrium. The
larynx, the ribs, &c. exhibit it in a very evident manner; it is
delicate, with fibres interlaced in all directions, less closely
united to the organs it covers, than the periosteum is to the bones,
because the cartilages having on their surface less numerous foramina,
it does not send to them as many fibrous elongations; hence a less
intimate relation between the life of the perichondrium and that of the
cartilage, than between that of the bone and its periosteum.

I have twice in a young dog removed from the thyroid its external
membrane, and closed the wound immediately, which has been cured
without apparent alteration in the organization of the cartilage; at
least it has continued to perform its functions. The same experiment
might easily be made on the cartilages of the ribs; I have not
attempted it. The perichondrium has appeared to me in many injections
to contain fewer blood vessels than the periosteum; its uses are
analogous to those of this last membrane.


ARTICLE SIXTH.

OF THE FIBROUS CAPSULES.

The fibrous capsules are infinitely more rare in the economy, than
they have heretofore been thought to be. The scapulo-humeral and the
ilio-femoral articulations are almost the only ones furnished with
them. Elsewhere there is nothing scarcely but synovial membranes.


I. _Forms of the Fibrous Capsules._

These capsules form a kind of cylindrical sac open at the two
extremities, attached by the circumference of its openings, around the
superior and inferior articular surfaces, intermixing at its insertion
with the periosteum. They are so much the more loose, as the motions
of the articulations are the more extended; that of the humerus, for
example, allows a much greater separation of the osseous articular
surfaces, than that of the femur; their length in fact is almost the
same. Now, as on the one hand, the neck of the first bone is much less
than that of the second, and as on the other, both these capsules are
inserted at the base of this neck, it follows that the extent of the
separation is in the inverse ratio of the length of the articular necks.

Much cellular texture surrounds these capsules externally, which the
tendinous fibres and even the tendons coming from the neighbouring
muscles, strengthen remarkably. They are sometimes open to allow
tendons to pass which are inserted in the bone between them and the
synovial membrane, an example of this is seen in the scapulo-humeral
articulation for the sub-scapularis. Anatomists who have observed
the insertion of the tendons in the capsules, have concluded from it,
that the muscles of these tendons were destined to prevent the capsule
from being pinched by the articular surfaces in motion. This appears
to me improbable; but at least the muscles are destined to prevent
the looseness of the capsule during the great motions, which would
have been weakened by this looseness; thus there are many of this
kind of muscles at the humeral capsule, whilst we see none of them at
the femoral, which is, as I have said, much less loose. Within, the
capsules are very closely united to the synovial membrane, especially
in adults; for in infants, this adhesion is less. Near their extremity
however this relation does not exist, because the synovial membrane
being reflected upon the cartilage, a triangular space is left
between it and the capsule which is attached to the bone, and as this
arrangement continues all round the articulation, there results from
it a kind of circular canal, filled with cellular texture, and covered
with vessels, which I have sometimes distended with an injection pushed
into a small opening made for the purpose.

The intimate union of the capsule with the synovial membrane prevents
its folds and also its contusion in the great articular motions.


II. _Functions of the Fibrous Capsules._

Why are the fibrous capsules found only around the first kind of
articulations? The reason of it is plain; as these articulations have
in all directions motions nearly equal, they should have on all sides
an equal resistance, whilst the others moving in one or two directions
only, the ligaments were unnecessary except at certain places, to limit
these motions. Hence why for example, the fibrous system is spread out
like a membrane around the ilio-femoral articulation, and collected
into distinct fasciæ around the femoro-tibial, where the synovial
membrane is almost everywhere bare.

We understand from all that has been said, that the only use of the
fibrous capsules is to strengthen the articular relations, and that
this use has no connexion with synovial exhalation.

When in luxations not reduced, the head of the bone has left the
articular cavity, a new membrane is formed around it in the cellular
texture which serves for a capsule; but this membrane has not the
texture of the former one. I have observed in two subjects, that no
fibre could be distinguished in it, that its texture was very analogous
to that of the different cysts that are often found in many parts of
the economy, of those especially that form round foreign bodies, the
presence of which is not a cause of suppuration, and that consequently
these preternatural capsules belong rather to the class of serous than
to that of the fibrous membranes.


ARTICLE SEVENTH.

OF THE FIBROUS SHEATHS.

The fibrous sheaths are, as we have said, partial or general.


I. _Partial Fibrous Sheaths._

The partial sheaths destined to a single tendon are of two sorts; one
runs a long course; such are those of the flexors of the foot and the
hand, which correspond to the whole concave surface of the phalanges;
the others form only a kind of rings, in which a tendon is reflected,
an example of which is seen in the great oblique muscle of the eye.

All in general form a semi-circle and make half of a canal which the
bone completes; so that the tendon slides in a canal half osseous
and half fibrous. This canal is lined by a synovial membrane, the
attachment of which to the fibrous sheath is equal to that of the
articular synovial membrane to its capsule. By their external surface,
the fibrous sheaths correspond with the neighbouring organs, to which
they are united by a loose cellular texture.

All these sheaths are of a very dense and compact texture; they are
stronger in proportion to the effort which the tendons can exert upon
them, than the fibrous capsules are in relation to the different
impulses which the bones can communicate to them and which tend to
rupture these capsules. They are confounded with the periosteum at
their two edges. Those of the flexors unite also by their extremity
with the expansion of the tendons; hence the very considerable fibrous
interlacing that is observed at the extremity of the last phalanges.

In the limbs, the flexors only have these sheaths; the extensors
are destitute of them. This arises first from this, that there are
two tendons of the first kind to each finger, whilst there is only
one of the second, and that consequently more force is necessary to
retain them in the first direction. In the second place, each extensor
tendon receives on its sides the insertion of the small tendons of the
interosseous muscles and the lumbricales, which by drawing it in an
opposite direction in the great motions, retain it in its place, and
thus compensate for the fibrous sheaths that are wanting. Finally the
efforts of the extensors are much less than those of the flexors, of
which they are as it were but a kind of moderators.


II. _General Fibrous Sheaths._

The general sheaths are seen especially at the wrist and the instep,
where they have the name of annular ligaments. They are destined to
confine many tendons together. As in these two places, all those of the
hand and the foot pass in a very narrow space, it is necessary that
they should be strongly supported. Besides, these sheaths serve also
sometimes to change their direction, as we see in those that go to the
thumb, whether to its palmar or its dorsal face, and which evidently
make an angle at the place of their passage under the sheath. The
tendons of the little finger have also an analogous arrangement.

These sheaths exhibit also two great modifications; in the one, as on
the anterior part of the wrist, all the tendons are found contiguous,
separated only by a kind of loose membrane which is placed between
them; in the others, as on the posterior part of the wrist, under the
general sheath, are found small fibrous partitions, which separate the
tendons from each other. In general, the resistance of these sheaths is
very considerable.


ARTICLE EIGHTH.

OF THE APONEUROSES.

We have distinguished aponeuroses as being of two classes, those for
covering and those for insertion.


I. _Of the Aponeuroses for Covering._

The aponeuroses for covering are general or partial.


_Aponeuroses for General Covering._

They are found around the limbs, whose muscles they tie down. The
arm, the fore-arm and the hand, the thigh, the leg and the foot, are
provided with them.


_Forms._

They are, in their conformation, analogous to the form of the limb,
which they in part determine, and which they especially maintain, by
preventing the displacement of the subjacent parts, a displacement
which would continually take place, from the laxity of the cutaneous
organ. Their thickness varies. In general, the greater the number of
the muscles they cover, the greater their thickness; hence why the
aponeurosis of the fascia lata is superior in this respect to the
brachial; why that of the fore-arm is thicker in front than behind; why
the plantar and palmar are so considerable, whilst hardly any fibres
are found on the back part of the foot and the hand. There are however
some exceptions to this rule; for example, the aponeurotic covering
of the posterior part of the leg is not in proportion to the power
of the gastrocnemii and solæus muscles; thus these muscles are more
than all the others exposed to displacements, frequently very painful,
which constitute cramp, and which it is necessary to distinguish from
the pains or numbness which result from the compression of one of the
nerves of the lower limbs, as of the sciatic, or the external plantar,
a compression produced by a bad position, or any other analogous cause.

Externally, the aponeuroses of the general covering are contiguous to
the integuments. A very loose texture unites them, so that the latter
can easily slide over them in external pressures. Immoveable between
these motions and those of the muscles, they entirely separate them; so
that the skin and the muscles that correspond to it, have not, in this
respect, any influence upon each other.

Within, these aponeuroses are in general loosely joined to the muscles
by cellular texture. Here and there they send between the different
muscular layers numerous elongations, which are afterwards attached
to the bone, and which, at the same time that they furnish points of
attachment, increase the solidity of the covering of the limb.


_Tensor Muscles._

The aponeuroses for general covering have almost all one or two
particular muscles that are inserted in them in whole or in part, and
which are destined to give them a degree of tension or relaxation
proportioned to the state of the limb. This arrangement is remarkable
in the insertion, 1st, of the great dorsal and pectoral muscles in
the brachial aponeurosis; 2d, of the biceps in that of the fore-arm;
3d, of the palmaris longus in the palmar; 4th, of the glutæus maximus
and of the fascia lata in the aponeuroses of that name; 5th, of the
semi-tendinosus, semi-membranosus and biceps in the tibial.

As in the great motions of the limbs, in which all the muscles are the
most liable to be displaced, these are necessarily in action, they
distend powerfully the aponeurosis, which thus reflects the motion that
is communicated to it, and resists especially every displacement. When
the limb is at rest, the tensor muscles cease their contraction, and
the aponeurosis is relaxed. I would observe, that the muscles attached
to the fibrous capsules, as to that of the humerus, for example,
perform for them the same functions, that the tensor muscles do for
their respective aponeuroses.

The colour of these last is a brilliant white; in this respect they
differ from all the fibrous organs thus far examined, and are analogous
to the tendons, from which they differ a little however in their
nature; in fact, they yield less quickly to maceration and ebullition;
their fibres are more stiff and resisting. There are no aponeuroses
exactly like the tendons, except those which are essentially formed by
their expansion or which are at their origin, as those spread upon the
anterior rectus of the thigh, those which are concealed in the fleshy
fibres of a muscle, and afterwards go out of it to become a tendon. In
certain parts of the limbs, as at the top of the arm, for example, the
aponeuroses of general covering are insensibly lost in the cellular
texture, without our being able to draw the line of demarcation. This
arrangement is almost peculiar to the fibrous system; at least I know
of no one which thus intermixes and loses its fibres in the cellular
texture; it is so much the more remarkable, as the nature of the two
textures is essentially different; they do not yield the same products,
and they have not the same organic arrangement.

The fibres of the general aponeuroses are only interlaced in two or
three directions; this interlacing is almost always very evident to
the naked eye. But I have observed that by plunging an aponeurosis
into boiling water, and leaving it there for some time, its fibres, in
the horny hardening they then undergo, become still much more evident.
This observation is moreover applicable to the whole fibrous system,
to its organs especially, whose texture but little apparent seems at
first view to be homogeneous. In this way, we distinguish very well the
fibres of the dura-mater.


_Functions._

The constant compression made upon the limbs by their aponeuroses,
besides the uses pointed out, has that of favouring the circulation
of the red and white fluids. Thus varices, which are very rare in the
deep veins which accompany the arteries, are extremely common in the
superficial ones placed beyond the influence of this compression, which
art imitates by the application of tight bandages, the effect of which
is so advantageous in many external diseases arising from the want of
tone, and the relaxation of the parts. I have uniformly observed that
the serous infiltrations always begin in the sub-cutaneous cellular
texture, that it is only in an advanced stage of dropsy, that we find
effusion in that which is under the aponeuroses, and that in general
it does not contain as much serum in proportion as the other. In
most of the great distensions of dropsical limbs, when the skin is
removed and the subjacent water has flown off, the limb covered by its
aponeurosis, is scarcely larger than in the ordinary state. The muscles
not protected by these coverings, like those situated on the sides of
the abdomen for example, become dropsical much more easily.


_Aponeuroses for Partial Covering._

These aponeuroses are met with in insulated parts, in front of the
abdomen, on the head, the back, &c.; they are usually destined to
retain in place a certain number of muscles which they do not surround
on all sides, like the preceding, but with which they correspond
only in one direction. Their thickness is much less than that of the
preceding ones; it is adapted to the efforts that they are to support.

All have a tensor muscle which proportions their degree of relaxation
or of tension to the effort of the neighbouring muscles. The anterior
rectus, by means of its intersections, and the pyramidalis, perform
this office for the abdominal aponeuroses; the small posterior
dorsocostals do it for that which covers the muscles of the vertebral
foramina; the auricular, the frontal and the occipital for that of the
cranium.

The aponeuroses of covering, whose use is limited to one muscle only,
like that, for example, of the temporal, want the tensor muscle, and
have consequently the same degree of tension always; it is on this
account no doubt that they have a very compact and thick texture, as
that which I have just mentioned is an example.

In general, the use of all the aponeuroses of covering whether general
or partial, relative to the compression of muscles, is required by
the displacements of which they would be susceptible in contracting,
displacements evident, 1st, when we place the hand upon a muscle in
action, and which is destitute of aponeurosis, as the masseter; 2d,
when a wound having injured a considerable part of an aponeurosis of
covering, the subjacent muscles become accidentally contiguous to
the integuments; 3d, when in an animal we lay bare the muscles of a
limb, and leave only the cellular texture to confine them, and in this
state excite their contraction; 4th, in certain wounds of the muscles
happening at the instant of their contraction, it is difficult to
probe these wounds, because in their relaxation the muscles taking a
different position, the relations change between the parts that formed
the two edges of the wound.


_Of the Aponeuroses of Insertion._

We have divided into three species the aponeuroses of insertion.


_Aponeuroses of Insertion with a Broad Surface._

They are very numerous. Sometimes they arise from the expansion of
a tendon, as we see in those of the anterior rectus of the thigh;
sometimes, as in the masseter, they derive their origin immediately
from the bones. Sometimes it is on one side only that the insertion is
made; at others it is on both at the same time, and then they appear
like partitions placed between the fleshy fasciæ, which they serve at
the same time to separate and unite, as we observe in the muscles that
arise from each of the condyles of the humerus.

These aponeuroses always receive in a very oblique direction the
insertion of the fleshy fibres. Their mutual adhesion is intimate; I
shall speak of it in treating of the tendons.

They have the great advantage of multiplying prodigiously the points
of insertion, without requiring great osseous surfaces. The width
of the whole of the temporal fossa would not be sufficient for the
masseter, if it was inserted by separate fibres. By means of the
aponeurotic partitions which receive its fibres and are afterwards
fixed in the bone, its insertion is concentrated upon one of the edges
of the zygomatic arch. Thus in general, all the very strong muscles,
whose fibres are consequently very numerous, are crossed by similar
aponeuroses, as the deltoid, the pterygoids, &c. are a proof.

Almost all these aponeuroses are exactly like the tendons; many
are continuous with them and then their fibres remain in the same
direction. In general, it is a character of these aponeuroses not to
have their fibres crossed in different directions, like those of the
aponeuroses of covering; the reason of it is plain; the fleshy fibres
to which they give attachment being all nearly in one direction, or at
least not crossing, it is necessary that these should be like them as
they are continuous with them.

I have made an experiment which shows very evidently the identity of
the tendons with these aponeuroses; it consists in macerating for
some days a tendon; it then becomes supple; its fibres separate; by
stretching in the direction of its width, it forms a kind of membrane
which it would be impossible to distinguish from a true aponeurosis.


_Aponeuroses of Insertion in the form of an Arch._

They are much more rare than the preceding. When a great vessel passes
under a muscle, nature employs this means, so as not to interrupt
the insertion of the fleshy fibres. The diaphragm for the aorta, the
solæus for the tibial artery, exhibit an arrangement of this kind.
The insertion is made on the convexity, and the passage of the vessel
under the concavity of the arch, both extremities of which are fixed
in the bone. It has been thought for a long time that the arteries
could be compressed under these arches; and hence the explanation of
popliteal aneurisms, of apoplexy by the reflux towards the head of the
blood interrupted in the aorta, &c. But it is very evident that by
contracting, the fleshy fibres would enlarge the passage, instead of
contracting it, since the necessary effect of these contractions is to
enlarge in all directions the aponeurotic curve, an effect which would
be directly opposite, if their insertion was made at the concavity.
These aponeuroses are strongly interlaced and very resisting.


_Aponeuroses of Insertion with Separate Fibres._

They are a collection of an infinite number of small fibrous bodies
wholly distinct from each other, which seem to be detached from the
periosteum, as the threads of velvet go off from their common woof.
Each is continuous with a fleshy fibre; so that when by maceration we
remove all those fibres, these small bodies become floating and are
seen perfectly well, especially when the periosteum which has been
detached is plunged into water.

It is evident that this mode of insertion on the part of the muscles
requires always broad osseous surfaces, since each fibre has a place of
its own; we have an example of it in the superior part of the iliacus,
of the anterior tibialis, of the temporal, &c. If all the muscles were
inserted in this manner, ten times more surface in the skeleton would
not be sufficient to receive them.


ARTICLE NINTH.

OF THE TENDONS.

The tendons are a kind of fibrous cords, intermediate to the muscles
and the bones, transmitting to the second the motion of the first, and
performing in this function a part wholly passive.


I. _Form of the Tendons._

Usually situated at the extremities of the fleshy fascia, they
sometimes however occupy the middle, as we see in the digastric
muscle; they are almost always found at the most moveable extremity,
that which serves for support having aponeuroses for insertion, as we
see especially on the fore-arm and the leg, of which all the muscles
inserted above by broad osseous or aponeurotic surfaces, terminate
below by a more or less slender tendon. From this arrangement result,
1st, little thickness at the extremity of the limbs, and consequently
facility in their motions; 2d, great resistance to external pressures
very frequent in this place, the fibrous texture being, as we have
said, very resisting; 3d, the concentration of the whole effort of a
muscle oftentimes very thick upon a very narrow osseous surface, and
for the same reason the extent and force of the motions of the bone.

The tendinous forms are usually round, no doubt because they are those
in which, with the least size the greatest quantity of matter enters.
Sometimes however as in the tendons of the extensors of the leg and the
fore-arm, they are flat.

Sometimes bifurcated or divided into many secondary elongations, the
tendons are inserted into the bones, or receive fleshy fibres in two or
many different points. All are covered by a loose texture which allows
them to slide easily upon each other, or upon the neighbouring parts.
Sometimes this texture is wanting, and then the synovial capsules
surround them to favour their motions. Their extremity, in which the
fleshy fibres are fixed, receives these fibres differently. Sometimes
it is to one side only that they are attached; hence the semi-penniform
muscles; at other times it is to both sides at the same time; this
constitutes the penniform. Frequently the tendon is buried so deep in
them, that it cannot be laid bare, but by dividing them longitudinally.

The adhesion is very great between the fleshy and tendinous fibre.
Yet by macerating them a long time or subjecting them to ebullition,
they gradually separate from each other. I have observed that in young
subjects the union was much less intimate; thus by scraping at this age
the tendon with a scalpel, we remove from it the muscle, without its
ever appearing again; the polish is almost the same where the fibres
are inserted, as where they are naturally wanting. The extremity of the
tendon fixed to the bone, intermixes with the periosteum as it usually
expands; so that it is with this membrane, and not with the bone
itself, that the tendon makes part, because in fact it is the membrane
which is of the same nature; thus if it finds an analogous membrane,
it fixes to it equally, as we see in the insertion of the straight and
oblique muscles in the sclerotica, of the ischio and bulbo-cavernous
ones in the membrane of the corpus cavernosum. In general the tendons
never unite but to fibrous membranes; the serous, the mucous, every
organ in a word, foreign to the fibrous system, is also heterogeneous
to them.


II. _Organization of the Tendons._

The fibrous texture is extremely compact in the tendons; many appear
homogeneous at first view; but by examining them with care, we soon
distinguish fibres, connected by a small quantity of compact cellular
texture. Ebullition renders these fibres very evident; when we plunge
suddenly the tendon into boiling water at the place where it has
been cut transversely, they become a little thicker at this divided
extremity, swell as it were and are thus very evident. At the place
where they expand to form an aponeurosis or to unite to the periosteum,
these fibres can be distinctly seen without any preparation. On the
other hand, as we can always, as I have said, reduce artificially a
macerated tendon to an aponeurosis, and as in this state of maceration,
soft and loose, it yields to all the forms we wish to give it, it is
an excellent means of distinguishing the tendinous fibres. In this
experiment so easily repeated, I have never seen the spiral form of the
tendinous cylinders, of which some modern authors have spoken. These
fibres are in the tendon as at the place where they separate to form an
aponeurosis, that is to say in a right line.

Blood scarcely enters the vascular system of the tendons; but in some
inflammations, they are wholly penetrated by it. I have seen one of
those of the extensors, laid bare in a whitlow, so red, that it had
the appearance of a phlegmon. Yet I observed that this colour was not,
as in many other inflamed organs, dependant on the small red striæ,
an indication that the exhalants are filled with blood; but it was
uniform, as for example a body dyed red. In general, it appears that
of the whole fibrous system, it is the tendons which have the least
energetic degree of vitality, and the most obscure vital forces. By
dissecting them in a living animal I have found that they have exactly
the same arrangement as in the dead body; the white fluids that
penetrate them do not flow under the scalpel; they are dry and can be
removed by layers. They appear to have a very low temperature; for,
in general, the degree of heat of an organ is in proportion to the
quantity of blood vessels it receives.

If in the body they are at the general temperature, it is only because
the neighbouring organs communicate theirs to them. Caloric is not
disengaged in their texture.

The tendons have a remarkable affinity to gelatine and even the
phosphate of lime; where they slide upon a bone, and where they suffer
a great friction, they exhibit a hardness which authors attribute to
pressure, by comparing it to the callous hardening of the sole of the
feet, but which is owing evidently to an exhalation in the tendinous
texture of the two preceding substances, an exhalation which the motion
produces and from which arises a real ossification.

It is thus as we have said, that the different sesamoid bones are
formed, and the patella in particular, a bone the texture of which
evidently differs from that of the others, because in the midst of the
gelatine and of the phosphate of lime that penetrate it, there remains
in it a part of fibrous texture which is not seized upon by these
substances, and which is so considerable that its kind of vitality and
organization belong as much and more to that of the fibrous system,
than to that of the osseous.

Besides, if we detach the patella or any sesamoid bone, leaving with it
a tendinous portion of each side, and expose them to the action of an
acid, this calcareous substance is removed, the fibres of the bone are
exposed, and we see that they are a continuation of those of the tendon
which is then softened.

The muscles of organic life, and most of those which in animal life
form the sphincters, are destitute of tendons. This white texture,
those silver cords that are found in the heart, have not the nature of
the tendons of the limbs.


ARTICLE TENTH.

OF THE LIGAMENTS.

We have divided the ligaments into those with regular fasciæ, and into
those with irregular ones.


I. _Ligaments with Regular Fasciæ._

They are met with in general in almost all the moveable articulations,
and especially upon their sides; hence the name of lateral ligaments
by which most of them are designated. Some however are foreign to the
articulations, as we see an example in that extending from the coracoid
to the acromion process, in those which complete the different osseous
fissures, the orbitary for example.

These organs form fasciæ sometimes round, sometimes flat, fixed to, or
rather intermixed with the periosteum by their two extremities, easily
removed with it in childhood, holding to the bone in the adult by the
ossification of the internal layers of this membrane.

Their analogy with the tendons is very striking; the external
difference is that they hold to the periosteum at both sides, whilst on
one side the tendons are contiguous with the muscles. We see sometimes
that the same organ is a tendon at one age, and a ligament at another.
This arrangement is remarkable in the inferior ligament of the patella.
Yet there are, as we have remarked, differences of composition between
them. All result from an assemblage of fibres parallel in the middle,
diverging at the extremities, united by a cellular texture more loose
than that of the tendons, and which often contains some fatty flakes.
This substance is sometimes so abundant in them, that they have an
appearance analogous to that of the fatty muscles; I have made this
observation on the ligaments of the knee, in a subject elsewhere very
thin.

There are some blood vessels in the ligaments. In certain diseases
of the articulations, their vascular system is developed in a very
remarkable manner, and they are penetrated by a great quantity of
blood; no nerve is discoverable in them.

Sometimes the ligamentary texture is changed into a matter like lard,
in which every kind of fibre disappears, which rarely returns to
its primitive state, and which is met with almost always in organic
affections, fatal to the patient.

The ligaments unite strongly the osseous surfaces, prevent their
displacement, and yet allow easy motions; a double function which they
perform in virtue of a double property, of their resistance on the
one part, of their softness and flexibility on the other; sometimes
externally, they serve for some muscular insertions.


II. _Of Ligaments with Irregular Fasciæ._

These are irregular fibres scattered here and there upon the osseous
surfaces, without any order, intermixed in different directions between
the sacrum and the ilium, upon the summit of the acromion, &c. We see
many of these fibres, around some of the moveable articulations; much
cellular texture separates them. They cannot offer any general views.

In general, the fibrous system is not as regularly organized in the
ligaments as it is in the tendons, as the muscular system is in the
muscles, &c. In the ligaments even with regular fasciæ, we often see
fibres going in different directions, separating from the principal
fascia, without any very distinct order.



FIBRO-CARTILAGINOUS SYSTEM.


The fibro-cartilaginous system is composed of different organs which
anatomists have sometimes placed among the cartilages, and sometimes
among the ligaments, because they in fact partake of the nature of
both. I make a system of them between the two preceding ones, a
knowledge of which will facilitate the understanding of this.


ARTICLE FIRST.

OF THE FORMS OF THE FIBRO-CARTILAGINOUS SYSTEM.

We may divide the fibro-cartilaginous organs into three classes.

The first comprehends those which are found in the ears, the alæ of
the nose, the trachea, the eye-lids, &c. They are very delicate, like
membranes, sometimes arranged in an uniform manner, sometimes bent in
various directions. As neither their position nor functions have any
thing in common, we cannot give them a denomination derived from their
forms. We may designate these substances by the name of membranous
fibro-cartilages. Besides it is not only in its form, but also in its
nature, that this class differs from the others, as we shall see.

In the second class are ranked the inter-articular substances, which
occupy the interstices of the moveable articulations, whether they
are in part loose in the cavity, like those of the knee, of the lower
jaw, &c. and go in different directions according to the motions, or
whether, like that of the body of the vertebræ, they are fixed in a
solid, though moveable manner, on the osseous surfaces. These organs
are in general thicker than the preceding, very various in their form,
representing commonly a kind of laminæ, sometimes perforated through
the middle in the articular cavities, arranged in very thick fasciæ,
and formed like the body of the vertebræ in the vertebral column. We
may designate them under the name of articular fibro-cartilages.

I refer to the third class certain portions of the periosteum in which
the nature of this membrane is entirely changed, becomes penetrated
with gelatine and exhibits an aspect at first analogous to that of
the cartilages, but in which it is easy however to distinguish the
fibrous texture. These portions are found in the tendinous sheaths, in
which they facilitate the sliding of the tendons, and defend the bones
from their impression. They may be called the fibro-cartilages of the
tendinous sheaths.

These three classes of fibro-cartilages, though very analogous, have
not exactly the same structure, the same vital properties, nor the
same life; so that the system they form is not as homogeneous in its
different divisions, as the osseous, animal muscular systems, &c.


ARTICLE SECOND.

ORGANIZATION OF THE FIBRO-CARTILAGINOUS SYSTEM.


I. _Texture peculiar to the Organization of the Fibro-Cartilaginous
System._

The texture peculiar to the organization of the fibro-cartilaginous
system is composed, as its name indicates, of a fibrous substance, more
than of a true cartilage.

The fibrous substance is as the base of the organ. We distinguish this
base very plainly in the fibro-cartilages of the tendinous grooves and
of the articulations, in those especially of the body of the vertebræ;
it is much less apparent in the membranous fibro-cartilages. Its
fibres are sometimes interlaced, sometimes parallel. In general its
nature is exactly the same as in the fibrous system, hard, resisting,
dense and compact, hence the very great force which the organs of
this system have; hence, 1st, the solidity with which the vertebræ
are kept together; 2d, the difficulty of rupturing, or tearing the
fibro-cartilages of the knee, the jaw, the clavicle, &c.; 3d, the
resistance which that of the radius makes to the inferior luxations of
this bone, luxations which in the forced pronations of this bone have
great tendency to take place, and which cannot without the rupture of
this fibro-cartilage. I have seen an example of a similar displacement
not reduced; the fibro-cartilage was entirely gone; 4th, by bending
the true cartilages they break nearly like a radish; these organs
on the contrary bend in all directions, and resist the agents that
stretch them; 5th, we see men imprudently raise children by their
ears, the fibro-cartilages of which easily support the weight of the
whole body. I am persuaded that those of the nose would do the same.
6th. We know that in the aneurisms of the pectoral or the abdominal
aorta, the bodies even of the vertebræ are much more quickly worn, and
consequently resist less than the substances which unite them.

The cartilaginous portion appears to be interposed between the fibres,
the interstices of which it fills. It is very evident especially in
the articular fibro-cartilages and in those of the grooves; it is
from it that they borrow the white colour that characterizes them,
the inorganic appearance that a section of them exhibits in many
places, and the elasticity which they have. Subjected to ebullition,
the articular fibro-cartilages, like those of the tendinous grooves,
become yellow, transparent, melt into gelatine, though with much more
difficulty than the true cartilages.

As to the membranous fibro-cartilages of the ear, the nose, the
trachea, the epiglottis and the eye-lids, their composition appears to
be very different. The action of boiling water does not reduce them to
a gelatinous state, at least in an evident manner; they remain white,
soften a little, appear wholly different from a fibrous organ or the
other fibro-cartilaginous organs boiled, which dissolve after becoming
yellow and semi-transparent. The inspection of the ears of animals
that are brought on our tables clearly proves this; I have frequently
confirmed it in my experiments. I know but few of the textures in the
economy that resemble this. When it has been boiled a little while, the
kind of periosteum which surrounds it is detached from it; it breaks
itself and cracks in many places; the rings of the trachea especially
exhibit an example of this last phenomenon.

Exposed for some days to maceration, this texture, from being white,
becomes of a very evident red. This colour is deeper than that which
the cartilages of ossification acquire in water; does it arise from
the same causes? I know not.

When the intervertebral fibro-cartilages are macerated, their fibrous
laminæ take also their reddish tinge, which I have not seen in the
other articular fibro-cartilages, especially in those of the knee.

Drying makes the membranous fibro-cartilages hard and brittle; they do
not take then the yellow colour of the dried tendons and aponeuroses;
they have a peculiar appearance.

Subjected to this experiment, the intervertebral substances acquire
a remarkable transparency, different also from that of the fibrous
system, without the yellowish tinge. In the first days of their
maceration, these substances, when they have been entirely detached
from the vertebræ, swell, rise up and form a kind of hollow cone, the
summit of which is made by the middle which especially swells, and the
base by the circumference which remains nearly in the natural state.

Most of the fibro-cartilages want in general the perichondrium; this
is evident in those of the tendinous grooves in which the bone on one
side and the synovial membrane on the other cover the organ, in those
of the articulations which this membrane surrounds on both sides, and
in those of the vertebræ to which only the anterior and posterior
vertebral ligaments correspond. As to the membranous fibro-cartilages,
there is upon them a very distinct fibrous texture; it is thick,
closely united to the peculiar texture of the organ, easily seen by
maceration, which whitens it in an evident manner, and which thus makes
it wholly different from the fibro-cartilaginous texture which is in
the middle. By cutting a fibro-cartilage of the ear, the nose, that of
the epiglottis, &c. after they have remained in water, this fact is
made very clear, especially during the period in which they have the
redness that I have pointed out.

The fibro-cartilaginous system appears to have nearly the same
relations with the digestive juices, as the fibrous and cartilaginous
systems, of the nature of which it partakes; it is altered with
difficulty by those juices in a crude state. Boiling, by softening,
makes it yield more to their action; it becomes then more digestible.
In general, it gives an aliment less proper for nutrition, than that
furnished by many other systems.


II. _Parts common to the Organization of the Fibro-cartilaginous
System._

The common organs of the fibro-cartilages are not very conspicuous; the
cellular texture is in small quantity, and so compact as hardly to be
distinguished; maceration however renders it apparent.

But little blood enters their vascular system in the ordinary state;
I convinced myself of this by dissecting an animal killed for the
purpose by asphyxia, a disease in which the blood accumulating in
the capillaries intermediate to the arteries and the veins, towards
the head especially, renders these capillaries very evident; but in
inflammation, which is however rare in the fibro-cartilages, they are
very much injected. We can trace no nerves in them.


ARTICLE THIRD.

PROPERTIES OF THE FIBRO-CARTILAGINOUS SYSTEM.


I. _Physical Properties._

Elasticity belongs essentially to this system. This property is very
evident, 1st, in the fibro-cartilages of the ears, when we bend them;
2d, in those of the nose, when twisted in various directions; 3d, in
those of the trachea, when we compress them, or after having cut them
longitudinally, we separate the edges of the division, as is done in
tracheotomy, when the object is the extraction of a foreign body. It
performs an important use in the kind of vibration which is made in
the first in the perception of sounds, in the second in the production
of the voice; 4th, it is in virtue of their elasticity, that the
articular fibro-cartilages serve as a kind of cushions which favour,
by contracting and expanding, the motion of the osseous surfaces to
which they correspond; 5th, that those of the vertebræ in particular,
flattened during the day, re-act during rest, and thus make the
stature in the morning something more than it is in the evening; 6th,
finally in the sliding of the tendons upon their fibro-cartilages, the
elasticity of these last favours the motion in an evident manner.

This elasticity of the fibro-cartilages is united to a remarkable
suppleness; they bend in all directions without breaking. By the first
property they resemble especially the cartilaginous system; by the
second they approximate the fibrous. It is not astonishing that being
intermediate to these two systems in their texture, they should be so
also in their properties.


II. _Properties of Texture._

Extensibility is very often brought into action in the
fibro-cartilaginous system. I have seen a polypus that had so dilated
the anterior openings and consequently the fibro-cartilages of the
nostrils, that their diameter was at least treble. The external and
cartilaginous extremity of the meatus auditorius often exhibits from
the same cause, an analogous distension. In the various twistings of
the vertebral column, the portion of the fibro-cartilages corresponding
to the convexity of the curvatures, is evidently elongated, whilst
the opposite portion is contracted. This extensibility is moreover
subjected in many cases to the same law as in the fibrous system,
that is to say that it cannot be put into action but in a gradual and
insensible manner.

The contractility of texture is observed when, in the cases of which
I have spoken, the cause of distension disappears. Thus after the
extraction of the polypus mentioned, the nostril gradually resumes its
natural diameter. I have removed in a dog a tendon from its groove,
by cutting it at one extremity, and drawing it by the other, so as to
leave untouched and empty the sheath that contained it; this sheath
and the fibro-cartilage have gradually contracted and the cavity has
disappeared. In the carcinoma of the eye, in which the eye-lids were
not removed, the tarsi which become much elongated with these moveable
veils, gradually contract and resume their dimensions, after the
extirpation of the tumour which distended them. It is necessary however
to distinguish these phenomena from those which are the product of
elasticity; these last are prompt and sudden; the fibro-cartilage of
the ear, powerfully stretched, yields a little, and immediately goes
back again; the others, on the contrary, are characterized most often
by a remarkable slowness.


III. _Vital Properties._

All the vital properties appear to be but little developed in the
fibro-cartilages; there is no animal sensibility or contractility in
the natural state; the first appears however in inflammation. Organic
sensibility and insensible contractility are only found in the degree
necessary for nutrition. There is no sensible organic contractility.

This obscurity in the vital properties, gives to all the phenomena
of the life of the organs of which we are treating, a remarkable
slowness. I have observed that in making in the ears of a dog a
longitudinal section, and afterwards uniting the wound by a suture,
the skin, at the end of a few days, is entirely closed; but it is
only at the expiration of a much longer time, that the union of the
cartilage takes place below, as we can see by examining the parts after
the union of the integuments. I presume that the same thing happened
in the operation of tracheotomy formerly employed, in which the soft
parts forming at first the cicatrix, keep in contact the cartilaginous
semi-rings, which finally unite together.

It is also to this obscurity of the vital properties of the
fibro-cartilages, to their want of energy, that must undoubtedly be
referred the rareness of diseases of these organs. I know but few of
the organic systems in the economy, which are more rarely affected than
that of the fibro-cartilages of the nose, of the ears, the trachea, &c.
Gangrene attacks them with difficulty; they are scarcely altered by it,
whilst the soft parts which surround them are all already black. We
know but little of the kind of fluid they form in their suppuration.
The formation of pus appears to be even very rare in them, owing to
their want of vital activity.

As these organs are hardly ever diseased, we can with difficulty know
their sympathies; I am unable to cite an example of them.


ARTICLE FOURTH.

DEVELOPMENT OF THE FIBRO-CARTILAGINOUS SYSTEM.


I. _State of this System in the first age._

In the first periods of existence, the articular fibro-cartilages are
much developed, which appears to be the effect of the size of the
articulations at this period. In fact, as the extremities of the bones
are larger in proportion, whilst they are cartilaginous, than when they
are in the osseous state, the articulations are also proportionally
larger, and the organs they contain more developed.

The fibro-cartilages of the grooves, which are found almost all, as
we know, situated at the extremities of the long bones, are not, in
the first age distinct from the cartilages of ossification, which then
form these extremities. Confounded with them, they exhibit no line of
demarcation when we cut the lines at that place. This state continues
until complete ossification; then the fibro-cartilages of the grooves
remain insulated like the cartilages of the osseous extremities.

The interposed gelatinous portion appears to predominate, in childhood,
over the fibrous portion in the articular fibro-cartilages and in those
of the grooves. It is remarkable in the intervertebral substances,
in which this kind of mucilage which occupies the centre, is as to
quantity in the inverse ratio of the age, and in which the fibres are
also more developed. On the pubis, the whole is almost homogeneous in
the fœtus; the transverse fibres do not become very apparent till a
more advanced age. The articulations of the knee, the jaw, &c. have
in their fibro-cartilages, the same arrangement. Ebullition extracts
from them then a much greater quantity of gelatine; they have more the
smooth appearance of the cartilages.

The membranous fibro-cartilages are in general developed early, those
of the ear, the eyes and the nose especially. We see them very evident
in the fœtus. I have observed in two acephalous infants, that, like
all the other parts of the face, they were of a remarkable size, and
much greater than that of the ordinary state. Besides, the whole
fibro-cartilaginous system is, in the fœtus, extremely soft, supple and
unresisting.


II. _State of the Fibro-Cartilaginous System in the after ages._

This system becomes stronger as we advance in age; in old age, it
becomes hard and yields with difficulty from the peculiar nature of
its nutritive substances. It is to this circumstance that must be
attributed, 1st, the stiffness and inflexibility of the vertebral
column, whose fibro-cartilages keep all the pieces in a kind of
immobility; 2d, a part of the difficulties which an old person
experiences in hearing sounds, the concha not being able to vibrate
and reflect them as well as before; 3d, the less susceptibility of his
nostrils to dilate, the fibro-cartilages yielding less to the muscular
effort, which is besides also less; 4th, the difficulties of the
sliding of the tendons, their grooves being much less supple.

The fibro-cartilages have in general much less tendency to ossify in
old age, than the cartilages properly so called. I never saw this
phenomenon in the membranous ones; perhaps it arises from their
peculiar texture, and even the difference of the principles which go to
their composition, and from the small quantity of gelatine that enters
into them. Among the articular, there are scarcely any but those of
the vertebræ, which are sometimes entered by the phosphate of lime;
this is however rare. Those of the grooves are like the cartilages of
the moveable articulations, they constantly keep their nature; only
in extreme old age, their thickness appears to diminish a little by
the ossification of their laminæ which correspond to the bone, which
besides is not very evident.



MUSCULAR SYSTEM OF ANIMAL LIFE.


The general muscular system very evidently forms two great divisions,
differing essentially from each other, by the vital forces that animate
them, by their external forms, by their mode of organization, and
especially by the parts they perform, the one in animal life, and
the other in organic. We shall not then consider them together. Let
us begin by the examination of the muscles of animal life; these are
spread out in great number in the human body. No system as a whole, is
of more considerable size; no one occupies more space in the economy.
Besides the numerous regions that the muscles fill, they are generally
spread out under the skin, and partake, as it were, of the functions
of this organ, protect like it the subjacent parts, like it bear with
impunity the action of external bodies, and can even be divided in a
more or less considerable extent, without the general functions of
life suffering from it; which renders them very fit to defend the
deep-seated organs, whose lesion would be very injurious.


ARTICLE FIRST.

_Of the Forms of the Muscular System of Animal Life._

From their external forms, the muscles may be divided, like the bones,
into long, broad and short. Their arrangement varies according to
these three general forms.


I. _Forms of the Long Muscles._

The long muscles occupy in general the limbs, to the conformation
of which theirs is accommodated. Separated from the skin by the
aponeuroses, from the bone by the periosteum, they are situated in a
sort of fibrous gutter, which retains them powerfully, and in which
they are arranged in layers more or less numerous, the deep ones are
confined in their place by the superficial ones, which, in their turn,
have the aponeuroses to support them. These last are very long; they
commonly belong to the motions of three or four bones and even more,
examples of which we have in the sartorius, the semi-tendinosus and
membranosus, the biceps, the flexors and the extensors. As they become
deeper, they are also shorter and generally destined to the motions of
two bones only, as the adductors, the pectineus, &c. are a proof.

Cellular layers separate them; they are loose where great motions take
place, more compact where these motions are less, very thick where
vessels and nerves go between the muscular fasciculi. Often spaces more
or less considerable, filled with cellular texture, separate these
fasciculi from each other. We divide the long muscles into simple and
compound. They are simple when a single fasciculus forms them, compound
when they arise from the union of many. These fasciculi are found then
in two different manners; sometimes in fact its division is at the top
of the muscle, as we see in the brachial and femoral biceps; sometimes
it is at the inferior part, at the most moveable side that this
division is met with, as in the flexor and extensor muscles of the leg
and the fore-arm.

The long muscles often separate from each other, are sometimes held
together by means of aponeuroses, which confound a more or less
considerable portion of two, three and even four of these neighbouring
organs. The origin of the muscles of the internal and external
tuberosities of the humerus exhibits this arrangement, whence results
an essential advantage in the general motions of the limb. Then in fact
the contraction of each muscle serves, both to cause a motion below in
the moveable part to which it is attached, and to strengthen above the
fixed point of the neighbouring muscles which contract at the same time
with it.

Every long muscle is in general thicker in its middle than at its
extremities, a form which arises from the manner of the insertion of
the fleshy fibres, which arising above and terminating below, some
successively below others, are so much the less numerous as we approach
nearer each extremity, whilst in the middle they are all found in
juxta-position. The anterior rectus, the long supinator, the external
radial muscles, &c. have manifestly this arrangement.

There is a particular kind of long muscles, which has no analogy but
in external appearance with that of the muscles of the limbs. They
are those that are embedded in front and especially behind the spine.
Though they appear simple at first view, these muscles have as many
distinct fasciculi as there are vertebræ. The transversalis colli, the
sacro-lumbalis, the longus colli, &c. represent very well an elongated
fasciculus like the sartorius, the anterior rectus of the thigh, &c.;
but the structure of this fasciculus has nothing in common with that of
these muscles; it is a series of small fasciculi, which have each their
distinct origin and termination, and which appear to be confounded into
one muscle only because they are in juxta-position.


II. _Forms of the Broad Muscles._

The broad muscles occupy in general the parietes of the cavities of the
animal economy, those of the thorax and abdomen especially. They form
in part, these parietes, defend the internal organs, and at the same
time by their motions assist their functions.

Their thickness is not great; most of them appear like muscular
membranes, sometimes arranged in layers, as in the abdomen, sometimes
covering the long muscles, as on the back; they are in the first case,
much more extensive superficially than deeper seated.

Whenever abroad muscle arises and terminates on one of the great
cavities, it preserves everywhere nearly its breadth, because it has a
large surface for its insertion. But if from a cavity it goes to a long
bone, or to a small apophysis, then its fibres gradually approximate;
it loses its breadth, increases in thickness, and terminates in an
angle which is succeeded by a tendon, which concentrates into a
very small space fibres widely scattered on the side of the cavity.
The great dorsal and pectoral muscles present us an example of this
arrangement, which is met with also in the iliacus, in the glutæi
medius and minimus. The broad muscles of the pectoral cavity have a
peculiar arrangement which the ribs require; their origin takes place
by serrated points fixed to these bones, and separated by spaces
between them.

The broad muscles are most often simple; many rarely unite to form
compound ones. Different cellular layers separate them, like the long
muscles; but they are hardly ever like them covered by aponeuroses; the
greatest number is merely subjacent to the integuments; the reason is
that their form naturally protects them from these displacements, of
which we have spoken in the article on aponeuroses, and which, without
these membranes, would be so frequent in the long muscles. I do not
know that the cramp has ever been observed in those of which we are
treating. When the abdominal muscles are laid bare by incisions made
through the integuments of a living animal, I have observed, that in
contracting, the bulk of each preserves the same place.


III. _Forms of the Short Muscles._

The short muscles are those in which the three dimensions are nearly
equal, having a thickness in proportion to their width and their
length. They are found in general in the places, where is required on
the one hand much power, and on the other small extent of motion; thus
around the temporo-maxillary articulation the masseter and pterygoids,
around the ischio-femoral the quadratus the gemini the obturators, &c.
around the scapulo-humeral the supra-spinalis and the teres minor,
in the hand the muscles of the palmar eminences, in the foot various
fleshy fasciculi, in the vertebral column the interspinal, in the head
the small and great anterior, posterior and lateral recti, exhibit
more or less regularly the form of which we are treating, and answer
the double object that I have indicated, on the one hand by the very
considerable number and on the other by the shortness of their fibres.

The short muscles are, more often than the broad, united to each
other, either in their origin or termination, as we see in the foot
and the hand. Sometimes they are of a triangular form, as in these two
parts; sometimes they approach to the form of a cube, of which there
is an example in the masseter and pterygoid muscles. In general they
are rarely covered by aponeuroses, undoubtedly because the shortness
of their fibres prevents them from being liable in a great degree to
considerable displacements.

Besides, the division of the muscles into long, broad and short,
is, like that of the bones, subject to an infinite number of
modifications. In fact many of these organs have mixed characters; thus
the sub-scapularis and the infra-spinalis have a form intermediate to
the broad and short one; thus the cruræus, the gemelli of the leg, &c.
cannot be considered precisely long or broad muscles. Nature varies,
according to the functions of the organs, the conformation of the
agents of their motions, and we can only establish approximations in
our anatomical divisions.


ARTICLE SECOND.

ORGANIZATION OF THE MUSCULAR SYSTEM OF ANIMAL LIFE.

The part peculiar to a muscle is what is commonly called the muscular
fibre; the vessels, the nerves, the exhalants, the absorbents and the
cellular texture, which is very abundant around this fibre, form its
common parts.


I. _Texture peculiar to the Organization of the Muscular System of
Animal Life._

The muscular fibre is red, soft, of an uniform size in the great
and small muscles, sometimes disposed in very evident fasciculi and
separated from each other by remarkable grooves, as in the gluteus
maximus, the deltoid, &c. sometimes more equally in juxta-position, as
in most of the broad muscles, always united to many others of the same
nature like it, easily by this union distinguished by the naked eye,
but eluding microscopic researches when we wish to examine it in a
separate manner, so great is its tenuity. Notwithstanding this extreme
tenuity, an infinite number of researches have been made during the
last age, to determine with precision the size of this fibre. On this
point may be read the result of the labours of Leuwenhoek, Muysk, &c. I
shall not give here this result, because science can draw nothing from
it, and because we cannot rely upon its accuracy; of what importance
moreover is the precise size of the muscular fibre? its knowledge would
add nothing to our physiological views upon the motion of the muscles.

Every muscular fibre runs its course without bifurcating or dividing
in any manner, though many have thought otherwise; it is found only
in juxta-position to those which are near it, and not intermixed, as
often happens in the fibrous system; an arrangement that was rendered
necessary by the insulated motions it performs; for the general
contraction of a muscle is the union of many partial contractions,
wholly distinct and independent of each other.

The length of the fleshy fibres varies very much. If we examine in
general the mass which they form by their union, we observe that this
mass has sometimes much greater extent than the tendinous portion of
the muscle, as the biceps, the coraco-brachialis, the rectus internus
femoris, &c.; that sometimes its length is much less as in the small
plantar and palmar muscles, &c.; and that sometimes it is about equal,
as in the external radial, &c. If from the examination of the fleshy
mass, we pass to that of the separate fibres that compose it, we
see that the length of the first is rarely the same as that of the
second. There are hardly any but the sartorius and some analogous
muscles, whose fibres run the whole extent of the fleshy, mass; in
almost all the others, they are found obliquely arranged between two
aponeuroses, or between a tendon and an aponeurosis; so that though
each of them may be very short, as a whole they are very long, as we
observe in the anterior rectus of the thigh, the semi-membranosus, &c.
This arrangement may also arise from various tendinous intersections,
which cut at different distances the length of the fibres. In general,
the muscles which owe their length to long fibres, have great extent
and very little power of motion; whilst those with short fibres, but
multiplied so as to give great length as a whole, are remarkable for
an opposite character. And this is the reason: all the fibres being
equally large, whatever may be their length, have the same degree of
force; it is evident then that this force considered in a muscle as
a whole, is measured by the number of its fibres. On the other hand,
the longer a fibre is, the more it shortens in its contraction; then
by contracting, a muscle brings its attachments so much the nearer in
proportion as its fibres are longer.

All the fibres of the voluntary muscles are straight, those of the
sphincters excepted. They are either parallel as in the rhomboids, or
obliquely situated in relation to each other, as in the great pectoral.
Sometimes in the same muscle many sets cross each other in different
directions, as we see in the masseter; but this crossing is wholly
different from that of the involuntary muscles in which there is more
crossing of fibres, whilst here we see only fasciculi in different
directions, in juxta-position to each other.

I shall not speak here of the cylindrical form according to some, and
the globular one according to others, of the fleshy fibre; inspection
teaches us nothing upon this point; how then can we make that an object
of research and give an opinion upon it, which has no real foundation?
Let us say thus much of the intimate nature of this fibre, upon which
so much has been written. It is unknown to us, and all that has been
said upon its continuity with the vascular and nervous extremities,
upon its pretended cavity, upon the marrow, which according to some
filled it, &c. is only a collection of vague ideas, which nothing
positive confirms, and to which a methodical mind would not attend. Let
us begin to study nature where she begins to come under our senses. I
would compare the anatomical researches upon the intimate structure
of the organs, to the physiological researches upon the first causes
of the functions. In both we are without guides, without precise and
accurate data; why then give ourselves up to them?

All that we can know upon the nature of the muscular fibre, is that it
is peculiar, that it is not the same as that of the nerves, nor as that
of the vessels, nor as that of the tendons or the cellular texture; for
where there is identity of nature, there ought to be identity of vital
properties and of texture. Now we shall see that all these systems
differ essentially from each other in this point of view; there can
be between them no analogy in relation to their nature, whence the
properties are always derived.

The muscular texture is remarkable for its softness and small degree
of resistance. It is by this that it is essentially different from the
fibrous texture. It breaks with ease in the dead body. In the living,
this rupture is rare, because the contraction which exists in all the
violent efforts, gives it a density, by which it gains an enormous
increase of resistance, but which it loses when it is no longer in
a state of contraction. There are however examples of the rupture
of muscles; it is principally in the rectus abdominis and quadratus
lumborum that they take place. I have seen one in this last. Observe
that this muscle and all those placed between the ribs and the pelvis,
are much disposed, from their situation, to these ruptures. In fact,
when the pelvis and the thorax are carried in an opposite direction,
these muscles are so much the more violently stretched, as in these
motions all the superior part of the body forms with the thorax, a
great lever, which is moved in an opposite direction to another great
lever, which is formed by the pelvis and all the inferior parts; now
from their length, these levers are capable of receiving a very great
motion, of communicating it consequently to the abdominal muscles which
are stretched between the two, and which serve to unite them. Hence how
in a violent inclination to the right, the quadratus of the left side
can be torn, &c. Observe that but few of the muscles in the economy are
found between two levers so great, consequently are capable of being
so much distended, and especially of being so with a force greater
than that of their contraction; for every muscular rupture supposes
the excess of the external motion, which distends, over that of the
fleshy fibres which contract to oppose this distension. If the external
efforts were concentrated upon a single muscle, they would be able more
often to overcome the resistance; but almost always many partake of the
effort to support and the resistance to oppose.


_Composition of the Muscular Texture._

The muscular texture has been with chemists, a more particular object
of research than most of the other organized textures. They have
examined it under all its relations. I refer to their works, to that
of Fourcroy especially, for all which is not strictly relative to
the nature of this texture, for all which considers consequences not
applicable to physiology, which we can deduce from the knowledge of the
principles that enter into its composition.

Exposed to the action of the air, the muscular texture is affected in
two ways. 1st. It dries, if cut into thin slices, admitting of the
evaporation of the fluids it contains. Then its appearance is of a dull
brown; its fibres contract, it becomes thinner, hard and brittle. If
replunged into water within some days, even fifteen or thirty after its
drying, it resumes its primitive softness and form, and has a less deep
coloured tinge. The water that has been used for this softening is more
or less fetid, and similar to that of macerations. 2d. Exposed in too
great a mass to the air, the muscular texture does not dry, but becomes
putrid. Thus in making anatomical preparations by drying, care should
be taken to lessen the thickness of the fleshy parts, or to arrange
them so that the air can penetrate them everywhere. Putrefaction is
inevitable if the air is moist, if the evaporation of the fluids is
not quick enough to produce drying. When it becomes putrid, the muscle
assumes a green, livid colour; it exhales an offensive odour. Under the
influence of the same circumstances it becomes putrid much quicker than
the fibrous, the cartilaginous and the fibro-cartilaginous systems. The
odour that it exhales then is also very different from that of these
systems; a phosphoric light often escapes from it. A mass of putridity,
in which all the fibres have almost disappeared, takes the place of the
muscle, when putrefaction is advanced. This mass of putridity gradually
evaporates in part, and there remains a dark brown residue, which dries
and becomes hard and brittle, nearly like the muscle dried in the
ordinary state, though the appearance however may be very different.

Exposed to the action of water, the muscle undergoes different
phenomena, according as it is hot or cold. Cold water takes from it at
first its red colour, of which it appears to dissolve the principle. To
effect quickly this phenomenon, it is necessary to expose the flesh,
at first in thin layers, to the action of water that is often changed,
by placing a muscle for example under a fountain, in the current of a
river, or what is much better, by frequently expressing the water it
imbibes; for if we keep it in a vessel, its exterior only whitens a
little, and the interior preserves its colour. Water which has been
used to wash a muscle, looks like blood spread out in this fluid; it
contains the colouring matter, a little of the extractive substance,
gelatine, &c. I believe that of all the organs the muscle is that from
which we remove most easily its colour by artificial means. Ought we
to be astonished after this, if nature varies so evidently and so
frequently this colour by the phenomena of nutrition, as we soon shall
have occasion to remark? Kept in water at a moderate temperature,
the muscular texture remains for a long time without softening; it
finally does, and changes layer by layer into a kind of putridity
very different however from that which is formed in the open air, as
I have frequently observed in macerating the muscles in a cellar, the
temperature of which is uniform. At other times, instead of putrefying
thus, the muscle is changed, as Fourcroy has remarked, into a substance
like spermaceti; then its fibre is hard and solid. But all the muscles
when kept in water by no means exhibit this phenomenon. When it does
take place, very often a kind of reddish product, scattered here and
there on the surface of the muscle, and which is an evident effect of
decomposition, announces and afterwards accompanies this state, without
which also, it often takes place. Maceration in dissecting rooms
frequently exhibits this phenomenon.

When we have taken from the muscles their colouring substance by
repeated washings, there remains a white fibrous texture, from which
we can still extract albumen by ebullition, which rises in scum,
gelatine by suffering it to grow cold, extractive matter which has a
deep colour, by letting it settle, and some phosphoric salts. When
all these substances have disappeared, the residue of the muscle is
a fibrous substance, of a greyish colour, insoluble in warm water,
soluble in the weak acids, giving out much azote from the action of the
nitric acid, and presenting all the characters of the fibrin of the
blood. It appears, as Fourcroy has remarked, that this substance is
truly the nutritive substance of the muscle, that which, continually
exhaled and absorbed, contributes to its nutritive phenomena more
than all the others; it constitutes the essence of the muscle, it
especially characterizes it, as the phosphate of lime is the nutritive
characteristic matter of the bones. Is this substance formed in the
blood and carried from it to the muscle, or is it formed in the muscle
by nutrition, and thence carried to the blood? I know not. Whichever
may be the case, it appears to experience very great varieties in
its exhalation and absorption. The state of laxity, of cohesion, the
thousand various appearances of the muscular texture, appear to belong
in part to these varieties of proportion. Thus the phosphate of lime
or gelatine, diminished by nutrition, give to the bones softness or
brittleness.

It is in this fibrous and essential portion of the muscle, that
particularly resides the faculty of crisping by the action of caloric,
whether by plunging a muscle into boiling water, or exposing it to the
fire; for this crisping is as evident in the muscle deprived of its
colouring matter, its gelatine, its albumen, and even a portion of its
extractive substance as in the ordinary muscle. There is in general
a constant relation between the quantity of this fibrous substance
contained in the muscles, and the quantity that the blood contains of
it. In the strong, vigorous, sanguineous temperaments, as they are
called, the muscles are thick and much more fibrous. In all the slow
cachexiæ in which the blood is impoverished, the pulse small and feeble
and in which muscular nutrition has had time to share but little of the
fibrin of the blood, the muscles are small, weak, soft, &c. In general,
the muscles and the blood are always in constant relation, whilst other
systems often predominate and whilst this fluid seems to be in less
quantity in the economy.

Exposed for a long time to ebullition, as in common boiled meat, the
muscular texture, still united to the adjacent organs, and to its
common parts, gives, 1st, an albuminous scum which appears to arise
more from the lymph of the cells than from the muscle itself; 2d,
many fatty drops coming also especially from the cellular texture,
almost foreign consequently to the texture of the muscle, and which
swim on its surface; 3d, gelatine formed especially by the aponeurotic
intersections; 4th, an extractive substance which colours in part the
water in which it is boiled, gives it a peculiar taste and remains in
part adherent to the flesh to which it communicates a deep tinge wholly
different from that of raw flesh, a tinge which arises also from the
colouring matter of the muscle, and which moreover changes, when the
liquor cools, into a less deep and even a whitish tinge; 5th, various
salts which contribute much to the taste of the liquor, and the nature
of which chemists have ascertained. These are the natural phenomena of
the ebullition of the muscle.

The more extensive analysis of boiled flesh is not my province; but
what ought not to escape us here, are the phenomena of which the
fibre is the seat, whilst the preceding products are extracted,
whether from it, or the surrounding textures. These phenomena can
be referred to three periods. 1st. When the water is only tepid,
and even a little above the temperature of the body, it leaves the
muscular texture in the same state, or softens it a little. 2d. When
it approaches ebullition and begins to be covered with an albuminous
scum, the texture crisps, thickens and contracts and gives to the
muscle a density much greater than what is natural to it, and
augments considerably its resistance. I have observed that in this
state the muscles bear much greater weights than in a natural state.
They approximate, if we may so say, that remarkable density which
characterizes them when they contract in the living body, and which so
powerfully opposes their rupture. This condensation of the muscular
texture, which is prompt and sudden, increases till the period of
ebullition, when it is at its greatest height; it continues only for
a certain time. 3d. Gradually it diminishes, the fibres soften, and
are more easily torn than in their natural state. This softening, the
reverse of the hardening that precedes, is produced slowly and by
degrees. When arrived to a certain degree, the meat is rendered fit
for the table. Observe that then the muscle has not returned to the
state in which it was found before the hardening; among other phenomena
which distinguish it, the following is an essential one; it has lost
the power of crisping, of acquiring the horny hardness, from the action
of the concentrated acids, from alkohol or from caloric. In general it
becomes putrid more slowly. Its putrefaction does not give the same
odour. We know how much its taste differs. The principles it has lost
are undoubtedly one of the great causes of these differences.

When a muscle is exposed to an open fire, as in the roasting of meat,
the albumen is condensed, the gelatine melts, the fibrin filled with
juices softens, the extractive matter flows in part with the gelatine
and the salts held in solution; it is this that forms the gravy,
which is, as we know, very different from melted fat. The exterior of
the meat remains more dense than the interior; it is coloured by the
extractive substance. The interior loses in part its natural colour;
its consistence, its taste and its composition even change entirely.
The fibres, as in ebullition, lose the power of contracting and of
crisping from the action of strong stimuli and especially that of fire.

No part in the animal economy is more easily altered by the digestive
juices than the muscles. Almost all stomachs can bear boiled meat,
whilst many reject other organs when cooked. Carnivorous animals seize
upon the muscles of their prey in preference to the pectoral and
gastric viscera. Muscular flesh is with most people the most common
aliment, that with which they are never disgusted; it appears to be
the most nourishing of all those, which are afforded by the different
textures of animals; is it, as it has been said, because it contains
the most azote? Whatever may be the reason, the general part which the
muscular system takes in the digestion of all carnivorous animals, of
man especially, is remarkable. Yet all the parts of this system do
not appear to be equally agreeable to the taste of animals. It is,
for example, a singular fact, that those bodies which are brought to
our dissecting rooms, and which have been attacked by rats, are found
almost always exclusively gnawed in the muscles of the face.

Observe in regard to the use of the muscles in digestion, that it
is the portion of the fibrous system which adheres to them, and
forms, as it were, a part of them, I refer to the tendons, which
is the most easily altered by maceration, by ebullition and by the
digestive juices. Observe also that the great mass which the muscles
form in the body of all animals, of which they are more than one
third, presents to the carnivorous species ample materials for their
nutrition; thus nature, by multiplying these organs for the wants of
the individual which they move, seems to multiply them also for those
of the individuals which he is one day to nourish. In forming them in
each species, it labours for other species as well as for this. Who
knows if this general design, which observation finds in the series of
all animals, be not the cause of this remarkable predominance which
the muscles have over the other systems? Who knows, if nature would
not have diminished the powers of the animal mechanism which are so
numerous and so complicated in comparison with those of artificial
machines, who knows if she would not have simplified the means and
given the same results, if the motions of the animals had been the only
object of the formation of the muscles?

The sex has great influence on the quality of the flesh of animals. I
do not believe that any thing precise is known as to the nature of the
influence which the genital parts exert upon it; but the following are
remarkable facts upon this subject. The muscles of males are stronger
and better nourished, have more taste, resist boiling for a longer
time, are firmer, &c. Boiling water on the contrary alters quicker the
texture of females; it is more tender and gives to the liquor a less
strong taste. In the season of sexual intercourse, the muscular system
of the first has a peculiar odour, which often renders it disagreeable
even to the taste. It is an observation that is easily made in
quadrupeds, birds and fishes that are brought to our tables. Without
having as strong an odour, the flesh of the second becomes at this
period soft, flaccid and but little savoury.


II. _Parts common to the Organization of the Muscular System of Animal
Life._


_Cellular Texture._

The cellular texture is very abundant in the muscular system; I know
of no system that has a greater proportion of it. This texture forms
a very evident covering around each muscle. This covering is most
commonly loose, filled with fat, easily distended with air in emphysema
and serum in anasarca. At other times it is more dense, compact and
really arranged like a membrane. Such, for example, is the case with
that which covers the great oblique muscle of the abdomen, and the
dissection of which on this account, students at first find very
difficult. The other abdominal muscles, the trapezius, the serratus
major and the great dorsal exhibit also this arrangement. We might say
that in this way nature compensated for the aponeuroses, which are
wanting on the broad muscles of the trunk. Besides, this covering has
only a membranous appearance; it has nothing of its organization, it
disappears in the infiltration in which all the true membranes remain.

Besides this general covering of the muscle, each fasciculus has a less
covering, each fibre a still less one, and each smaller one a real
though almost insensible sheath. We can then represent the cellular
texture of the muscles as forming a series of coverings successively
decreasing. These coverings favour the motion of the fibres which they
separate, either by the serum of the cells, or by the fat they contain,
both fluids, by lubricating, allow them to slip more easily upon each
other. Frequently between these fibres, the cellular texture appears
to form a kind of cross pieces which go at right angles. We see this
arrangement especially in the proper extensor of the great toe, and
in the common extensor, the fleshy fasciculi of which are broad and
delicate when distended. In most of the thick muscles nothing similar
is observed.

The quantity of intermuscular cellular texture is remarkably variable.
In general, in all the broad muscles and in all the large, long
muscles, it is very abundant. It is less in proportion between the
fibres of those of the vertebral canals. Back of the neck, the splenii,
complexi, &c. have less of it than many others, especially in the
spaces that separate them.

Sometimes very considerable cellular elongations are found in the
middle of the muscles, and seem to divide them into two; such is that
which separates the clavicular portion of the great pectoral; this
has even sometimes embarrassed anatomists as to the division of these
organs.

The cellular texture in general fixes the muscles in their position;
the art of dissection proves it. The effusions of pus which often
perform the office of the scalpel, render also very evident this use,
which does not prevent the motion in all directions, that the great
extensibility of the cellular texture allows. The cellular texture
not only fixes the muscles to each other, but it also attaches each of
their fibres to neighbouring ones; it flattens them when they contract,
and elongates them when they are distended; if they are deprived of
it their motions become irregular and uncertain. I have many times
separated with a scalpel a muscle laid bare in a living animal, into
many small fasciculi; in afterwards making this muscle contract by
the irritation of the medulla, by means of a stilet introduced into
its canal, I have observed in an evident manner this irregularity of
motion. Cut longitudinally a muscle of an extremity from its superior
tendon to its inferior, so as to divide it into two or three entirely
distinct portions, irritate afterwards one of these portions, the
other or the two others will remain almost always at rest, whilst a
single irritated fibre in a sound muscle, puts in motion the whole of
that muscle. The section of the vessels and the nerves has no doubt a
little influence upon this phenomenon; but that of the cellular texture
certainly contributes to it also.

In dropsical subjects, the serum of the intermuscular texture is often
reddish; this phenomenon is owing to the action of this serum after
death upon the colouring substance. I believe that this can take place
during life only with great difficulty. The fat sometimes abounds in
this texture, to such a degree that the fleshy fibres disappear and
the fat only is visible; but oftentimes also the yellow appearance of
the muscular fibres, which is produced by the absence of the colouring
substance, is taken for this fatty state of the muscles. I have seen
the first state but rarely; the second is extremely frequent; we are
sometimes deceived at first view. But ebullition and combustion easily
prove, that the fat is wholly foreign to this want of colour of the
muscles examined in this state.


_Blood Vessels._

The arteries of the muscles are very apparent; they come from the
neighbouring trunks, penetrate the whole circumference of the organ,
more however towards its middle, than towards its extremities. They
run at first between the principal fasiculi, then divide and their
divisions go between the secondary fasciculi, subdivide and wind
between the fibres, and finally become capillaries and accompany
the small fibres, in which they deposit by the exhalant system the
nutritive matter. There are but few organs, which have, in proportion
to their size, more blood than the muscles.

The blood is essentially necessary to support their excitability, as we
shall see; it is that which colours the muscular texture, but not, as
it at first seems, by circulating in its texture. The circulating or
free portion contributes but little to it. It is the portion combined
with the muscular texture, that which contributes to its nutrition,
that gives it its colour; the following are proofs of it: 1st. The
fibres of the intestines are as much or more penetrated with the
circulating blood, than those of the muscles of animal life, and yet
their texture is evidently whitish, where these vessels are not found.
2d. Many animals with red and cold blood, frogs in particular, have
muscles almost white, and yet many red vessels run through this white
texture. 3d. I have observed that in animals destroyed by asphyxia,
the colouring substance does not change colour, no doubt because it is
slowly combined with the muscle by nutrition; that on the contrary, if
we cut a muscle of these animals in the last moments of life, whilst
the venous blood still circulates in the arterial system, this blood
flows out by black jets from the muscular arteries, the muscular
texture itself remaining red. This curious experiment, which I have
noticed in another work, is made by producing asphyxia in an animal by
compressing the trachea, or by intercepting the air in any other way in
this tube, whilst we examine the system of the muscles. When a muscle
has been exposed for some time to the contact of the air, to that of
oxygen especially, its red colour becomes evidently more brilliant.

The muscular vessels permit under certain circumstances the escape
of the blood they contain; hence different kinds of remarkable
hemorrhages, especially in scorbutic patients, sometimes in putrid
fevers, rarely or never in those diseases that are characterized by
an increase of vitality. Infiltrated with blood in preternatural
hemorrhages, particularly in false aneurisms, the muscles lose in
part their motion; this happens also in contusions, in which similar
infiltrations are observed.

The veins everywhere follow the arteries in the muscles; they have the
same distributions, and receive from the contractions of these organs
an essential assistance to their action. The throw of blood is more
powerful when the patient we have bled contracts his muscles, than
when he relaxes them; the fluid is as it were expressed, as from a wet
sponge which is squeezed. The arterial circulation does not exhibit
this phenomenon. I have observed that if we open the artery of the foot
of an animal, and by the irritation of the nerves, make the muscles of
the leg and thigh, through which this artery passes before reaching
the foot, contract powerfully, the throw of blood is not stronger than
during the relaxation.

I have many times injected the veins of the muscles of animal life with
ease, from the trunks towards the branches, which makes me believe,
notwithstanding what Haller has said, that in these organs, as in the
heart, the valves are less numerous than in many others. No doubt the
assistance the veins derive from their surrounding organs supplies the
place of these folds, or rather renders them useless, the weight of the
column of blood not making a great effort against the venous parietes.
The varices of the muscular veins are, as we know, extremely rare.
These veins are of two orders; one accompanies the arteries and follows
the same course, the others are spread superficially on the surface of
the organ, without having corresponding arteries.

There are absorbents and exhalants in the muscles; but we can with
difficulty trace the first, and the second cannot be perceived.


_Nerves._

Almost all the nerves of the muscles of animal life come from the
brain; the ganglions furnish a few of them; when this happens, as in
the neck, the pelvis, &c. besides the filaments coming from these
nervous centres, there are always filaments of cerebral nerves;
without this, these muscles would be involuntary. Few organs receive
more nerves in proportion to their size than the muscles. In general
the extensors appear to have rather fewer than the flexors; but the
difference is trifling. It is true that all the great nervous trunks
are in the direction of flexion, that in that of extension there are
only branches, as we see in the posterior part of the arm, of the
fore-arm, the vertebral column, &c. It is true also that this remark is
likewise applicable to the existence of the vessels, which are larger
and more numerous in the first than in the second direction; but this
greater number of vessels and nerves arises from this, that there are
many more flexors than extensors, that the first are stronger and have
more numerous fibres; so that each of these fibres hardly receives
more nervous or vascular filaments in one kind of muscles than in the
other. I think that there is but little foundation for what has been
said upon the difference of the strength of the fibres of the flexors
and of the extensors, upon the predominance of the first, &c. If these
are superior, it is either because they are more numerous, as in the
foot, the hand, &c. or more advantageously arranged, as in the trunk on
which the abdominal muscles act very far from the point of attachment
to bend the spine, whilst to extend it, the dorsal muscles exert their
action immediately at the side of this point of attachment, as also
in the neck, where the muscles that draw down the lower jaw and head
when this bone is fixed, are much further from the occipital condyles,
than the muscles which produce extension. Whatever may be the cause
of the superiority of the flexors, the fact cannot be doubted. 1st.
In hysterical convulsions, in those of infants, in all the spasmodic
motions in which the will has no part, the contractions take place much
more in the direction of flexion than in that of extension. 2d. In
old people the flexors finally become superior to the extensors; for
example, the fingers and toes are almost uniformly bent. 3d. In all the
motions, the power is always on the side of flexion.

The nerves enter the muscles of the extremities at a very acute angle,
because the nervous trunks are in the natural direction of these
organs. In the trunk, on the contrary, the nerves going from the spine,
the cervical especially, enter their muscles at almost a right angle or
one less evidently acute; this circumstance is of no importance. Each
branch in the fleshy fibres, is at first divided and then sub-divided
in their interstices, and afterwards lost in their texture. Does each
fibre receive a small nervous filament? We should be led to believe so
from this observation, that the principal branch being irritated, all
the fibres are put into action, no one remains inert. But on the other
hand, if we irritate one of them, all move also, which is certainly a
sympathetic phenomenon or one arising from the communication of the
cells.

Are the nerves deprived of their cellular coverings, and do they become
pulpy when they enter the muscles? Dissection has shewn me nothing like
it.


ARTICLE THIRD.

PROPERTIES OF THE MUSCULAR SYSTEM OF ANIMAL LIFE.

There are but few systems in the economy in which the vital properties
and those of texture are found in so great and evident a degree as in
this. It is from the muscles that examples must be selected to give a
precise and accurate idea of these properties. The physical properties
on the contrary are slightly marked in them; a remarkable softness
characterizes them; there is no elastic power in their texture; there
is but very little resistance from this texture after death; it is
from vitality that it derives the power that characterizes it in its
functions.


I. _Properties of Texture. Extensibility._

Extensibility is manifested in the animal muscular system under many
circumstances. The different motions of our parts render this property
evident. Such is in fact the arrangement of the muscular system,
that one of its portions cannot contract, without the distension of
another. The thigh being strongly bent, the semi-membranosus, the
semi-tendinosus and the biceps are elongated. The arm being carried
out, the great pectoral is extended, being raised, the great dorsal and
the teres major are stretched. All the great flexions bring into action
this property in the extensors; all the extensions render it evident
in the flexors. A muscle which is stretched by its antagonist is in a
state purely passive; it is as it were for a moment abandoned by its
contractility, or rather it possesses it, without its being brought
into action; it is made to obey the motion that is communicated to
it. Observe that in these cases, the distension is confined to the
fleshy portion, and the tendon has no connexion with it; it remains
the same, whatever may be the distance, of the points of attachment,
for these points are nearer or more remote in the different extensions
to which the muscles are exposed; the longest muscles yield the
easiest. The sartorius, the posterior muscles of the thigh, &c.
exhibit this phenomenon in an evident manner; as their position is
accommodated to it. In general all the muscles remarkable for their
length are superficial, and go most commonly to two articulations,
sometimes even to three or four, as in the limbs. Now the number of
these articulations renders the space comprised between the two points
of attachment susceptible of very great variations, which the great
extensibility of these muscles allows. It may be understood from what
has been said above, that it is to the length of the fleshy fibres and
to the whole length of the muscle, that its degree of extensibility is
to be referred. Those in which many aponeuroses are intermixed, and
which derive in part from these membranes or from tendons their length,
possess less of this property. Hence why, in the same motions, muscles
of the same total length become more or less short, more or less
elongated in their fleshy portion. Observe however that when on the one
hand the tendinous portion predominates much, and on the other that it
is very delicate, it yields a little, as we see in the small plantar
and palmar muscles.

If from the natural state we pass to the morbid, we see the muscular
extensibility manifested in a much more evident degree. In the
face, the air accumulated in the mouth, swells it by elongating the
buccinators; the various tumours of this cavity, as the fungous and
sarcomatous ones, often distend the small facial muscles in a manner
which would astonish us, if we considered the naturally small extent
of these muscles which are trebled and even quadrupled. The muscles of
the eye-lids and the eye in the large carcinomas of that organ, those
of the anterior part of the neck in the great swellings of the thyroid
gland, the great pectoral in large aneurisms or in other tumours of
the axilla, the abdominal muscles in pregnancy, in dropsy, in the
various tumours of the abdomen, &c. the broad and superficial muscles
of the back from wens that are under them, present us these phenomena
of distension in a remarkable manner. The muscles of the extremities
are less subject to them, because on the one hand fewer causes develop
tumours beneath them, and because on the other the aponeuroses do not
yield so easily to these phenomena.


_Contractility of Texture._

The contractility of texture is carried to the highest point in the
muscles. These organs have a continual tendency to contraction,
especially when by being elongated, they have surpassed their natural
size. This tendency is independent of the action of the nerves, and of
the irritable property of the muscular texture. It is influenced by
life, but it is not entirely dependent on it; it depends essentially
on the structure of the muscles. The remarkable phenomenon of the
antagonist muscles results from it. The following is this phenomenon.

Each moveable point of the animal frame is always between two opposite
muscular forces, between those of flexion and extension, of elevation
and depression, of adduction and abduction, of rotation without and
rotation within, &c. This opposition is a condition essential to the
motions; for in order to perform one of them, it is necessary that the
moveable point should be in the opposite motion; in order to bend,
it is necessary that it should be first extended, and reciprocally.
The two opposite positions which a moveable part takes, are for it
alternately the point of departure and the point of arrival; the two
extremes of these positions are the two limits between which it can
move. Now between these limits there is a middle point; it is the point
of rest of the moveable part; when it is found there, the muscles are
in their natural state; when it passes it, some are extended, others
are contracted, and such is their arrangement, that the contraction
and extension which take place in an opposite direction, are exactly
in direct ratio. Hence, in the reciprocal influence that the muscles
exert upon each other, they are alternately active and passive, power
and resistance, organs moved and organs which move. The effect of every
muscle which contracts is not then only to act upon the bone in which
it is inserted, but also upon the opposite muscle. Between two muscles
thus opposed, there is often no solid intermediate organs, as in the
lips, the linea alba, &c. The muscle of one side acts then directly
upon that which corresponds to it, in order to distend it. Now this
action of the muscles upon each other is precisely the phenomenon
of the antagonists; two muscles are such when one cannot contract
without elongating the other and vice versa. Let us examine in this
phenomenon the part of the contractility of texture; it is necessary to
distinguish its influence from that of the vital forces, which has not
been heretofore sufficiently done.

A muscle once placed in the middle position, can only be removed from
it by the influence of the vital forces, by the animal or sensible
organic contractility, because in this position the contractility
of texture of its antagonist is equal to its own, and there is
consequently required a force added to this to overcome that which is
opposed to it. But if the muscle is found in one of the two extreme
positions, for example in adduction, abduction, flexion, extension,
&c. then there will be an inequality of action in the antagonists, as
it respects the contractility of texture; the one most stretched,
will make in order to contract itself, an effort much greater than
that which is already contracted. To maintain the equilibrium, it
is necessary then that the vital forces continue to influence the
contracted muscles. Thus every extreme position of the limbs and of
any moveable part, cannot in an ordinary state be supported except
by the influence of the vital forces. When these forces cease to be
in action, immediately the contractility of texture of the elongated
muscle, which had a tendency to exert itself, but was prevented, exerts
itself, becomes efficacious, and draws back the moveable part to the
middle position, a position in which the equilibrium is restored. Hence
why in all the cases in which the cerebral influence has no power
over the muscles, in which they are not irritated by stimulants, the
limbs are uniformly found in a medium position between extension and
flexion, abduction and adduction, &c. This is the case in sleep, in the
fœtus, &c. I have shewn elsewhere how the osseous arrangement of each
articulation is adapted to this phenomenon, how every kind of relation
between the articular surfaces, except that of this medium position,
exhibits a forced state in which some ligaments are necessarily more
stretched than others, and in which the osseous surfaces are never in
so general contact as in this position. In certain fevers which have
so deleterious an influence upon the muscular life and texture, the
horizontal prostration and extension of the extremities do not arise
from an increase of the action of the extensors, but from the want of
energy of the flexors, which have not power to overcome the weight of
the limb; thus observe that every analogous attitude always coincides
with the signs of general weakness; this is the attitude of putrid
fevers, &c.

The section of a living muscle presents us with two phenomena which are
evidently the product of the contractility of texture.

1st. The two ends retract in opposite directions; there exists between
these divided ends a space proportional to the retraction. This
retraction is not in proportion, as has been thought, to the degrees of
the contractions of the muscle; if it was, it would be sufficient in
a transverse wound, in order to bring the divided edges together, to
place the limb in the greatest possible relaxation; now oftentimes, in
these cases, these ends still remain at a distance; then the retraction
is often superior to the greatest contraction of the muscle considered
in its natural state.

2d. The antagonist of the divided muscle which has no effort to
overcome, contracts and makes the moveable part incline from its side,
if there are not other muscles, which acting in the direction of the
first supply its functions. This last phenomenon takes place also to a
certain extent in paralysis of the face. The mouth is then drawn from
the sound side. I have observed however in this respect, that this
deviation is never as evident as it would be by the division of the
paralytic muscle, which has preserved its contractility of texture.
This remaining contractility forms a partial equilibrium with that of
the muscles of the sound side, during the absence of motions; thus
the deviations do not become very evident until the patients wish
to speak, until consequently the vital forces bring into action the
sound muscles, which the others cannot oppose. The paralysis of the
sterno-mastoideus exhibits for the whole head a phenomenon analogous to
that which the preceding muscles produce for the mouth. Strabismus also
oftentimes arises from this cause.

In general in all the phenomena, it is necessary to distinguish that
which belongs to the vital forces, from that which arises from the
contractility of texture. The muscles are antagonists as it respects
these forces, as well as it respects this contractility; now as the
contraction dependant on the nervous influence or irritability, is
much more conspicuous than that arising from the organic texture, the
phenomena of the antagonists are much more striking in paralysis, when
the sound muscles are brought into action in the first manner. It
appears that in many cases of paralysis, the contractility of texture
of the affected side is also a little altered; but it is never so
completely destroyed, that in the amputation of a paralyzed limb, there
is no muscular retraction. I have made this experiment upon a dog; the
nerves having been cut ten days before, and the limb having remained
immoveable since that period, the division of the muscles produced
a manifest separation between their edges; and even, in afterwards
cutting for the sake of comparison the limb that remained sound, I did
not find any difference.

It is especially when muscles have been first stretched, and this
stretching has ceased, that the contractility of texture becomes
evident. The puncture in ascites and an accouchement as it respects the
abdominal muscles, the opening of deep abscesses as it respects those
of the trunk, the extirpation of a tumour situated under any muscle,
&c. show us this property in action in a very striking manner. There
is however an observation to be made on this point, viz. that if the
extension has been of long continuance, or if it has been frequently
repeated, the subsequent contraction is much less, because the muscular
texture has been weakened by the painful state in which it has been;
hence, 1st, the flaccidity of the abdomen after repeated pregnancy; 2d,
the laxity of the scrotum, after the puncture of an old hydrocele; 3d,
I have seen at Desault's a man who was operated upon in Germany for a
fungus in the mouth, and who had, on that side on which the disease had
been, remarkable wrinkles, owing to the greater extent of the fleshy
part of that side, which could no longer contract like the other;
mastication, at this time could only be performed on the sound side;
4th, when women have had many children, the diaphragm is weakened by
repeated pressure, and hence in part the greater mobility of the ribs,
which compensate in some measure in females for the deficiency of
action of this muscle. I think that in many chronic affections of the
chest and abdomen, in which there is a long continued distension of
this muscle, physicians ought more than they do, to have regard to this
cause of difficulty of respiration, when the principle of distension no
longer exists, as after the evacuation of dropsies, &c.

The extent of the contractility of texture is in the muscles in
proportion to the length of the fibres; hence why in amputations,
the superficial part retracts more than the deep-seated; why in
sleep the phenomena of contractility of texture are very apparent
in the extremities, the muscles of which are very long; why, in the
antagonists, nature has in general opposed muscles of proportional
length; why consequently, a muscle with long fibres has rarely for
a counterpoise one with short ones, and vice versa. The flexors and
extensors of the arm, the fore-arm, the thigh and the leg are nearly
of the same extent; the rotators of the humerus within and without,
the first inserted into the sub-spinal depression, the others into the
sub-scapular, resemble each other also in this respect. The proportion
between the antagonists is still more remarkable on the face, where the
same muscles act most commonly in an opposite direction on each side of
the median line.

The quickness of the contractions, arising from the contractility of
texture, is not like that produced by the animal or sensible organic
contractility, which is uniformly more or less marked, according as
the nervous influence of the stimulant acts more or less strongly.
Every motion originating from the contractility of texture is slow,
uniform and regular; it is only when the muscular texture is weakened
that it diminishes; it does not increase except when this texture is
more developed; hence it follows that the varieties of quickness can
only be observed in different individuals, or in the same individual
at different periods, and not, as in the exercise of the vital forces,
from one instant to another. This is a great and remarkable difference
between the two species of properties.

Death weakens the contractility of texture but does not annihilate
it; a muscle being cut retracts a long time after life has left it.
Putrefaction alone puts a limit to the existence of this property.
It is the same with regard to extensibility. I would observe however
that while the muscles retain the vital heat, they have more power of
retraction, than when the chill of death has seized them.

Haller places on the same line and derives from the same principles,
the phenomena resulting from the contractility of texture, which,
with some slight differences, answers to his dead power, and those
produced by the action of the concentrated acids, alkohol, fire, &c.
on animal substances, which crisp, contract and acquire the horny
hardness from the effect of these different agents. But there are
many differences which essentially separate these phenomena from each
other. 1st. The contractility of texture is very slight in the organs
in which the faculty of having the horny hardness is very evident, for
example, in all the organs of the fibrous, fibro-cartilaginous, serous
systems, &c. &c. 2d. The contractility of texture is distributed in
very various degrees, to the different parts; from the muscles and the
skin, which possess the greatest degree of it, to the cartilages which
seem destitute of it, there are many variations; on the contrary, the
faculty of acquiring the horny hardness from the agents pointed out
is almost uniformly distributed, or at least its differences are much
less evident. 3d. One becomes nothing in dried organs, the other is
evidently preserved for many years, as parchment is a proof. 4th. The
first clearly receives an increase of power from life, especially in
the muscles; the second appears to be hardly modified by it. 5th. This
always exhibits sudden effects, rapid contractions. To feel the contact
of the fire, of the concentrated acids or alkohol, and to assume the
horny hardness, are two phenomena which the second brings together in
the animal parts; the contractility of texture, on the contrary, exerts
itself but slowly, as we have said. 6th. This last can never give
to the parts, the muscles especially, that remarkable density which
they exhibit in their horny hardening. 7th. The absence of extension
of the fibres is the only thing necessary for the contractility of
texture which has an unceasing tendency to activity; it requires on the
contrary in order to crisp the fibres, that they should be in contact
with a foreign body. I could add to these many proofs, in order to
establish an essential difference between the phenomena confounded by
the illustrious physiologist of Switzerland.


II. _Vital Properties._

The most of these properties perform a very important part in the
muscles. We shall first examine those of animal life, and afterwards
treat of those of organic.


_Properties of Animal Life. Sensibility._

Animal sensibility is that of all the vital properties which is the
most obscure in these organs, at least if we consider them in the
ordinary state. Cut transversely in amputations, in experiments upon
living animals, they do not experience any very painful sensation; it
is only when a nervous filament is touched, that pain is manifested.
The peculiar texture of the muscle is but slightly sensible; irritation
by chemical stimulants does not show much sensibility in it.

There is however a peculiar sensation, which in the muscles very
evidently belongs to this property; it is that which is experienced
after repeated contractions, and is called lassitude. After long
standing, it is in the thick bundle of lumbar muscles that this
sensation is especially felt. After walking, running, &c. if on a
horizontal plain, it is all the muscles of the lower extremities
which are more particularly fatigued; if on an ascending plain, it
is especially the flexors of the ilio-femoral articulation; if on
a descending one, it is the posterior muscles of the trunk. In the
employments which exercise particularly the superior extremities,
this sensation is often experienced in a remarkable manner, which
is certainly not owing to the compression made by the muscles in
contraction, upon the small nerves which run through them. In fact it
can take place without this antecedent contraction, as is observed
in the commencement of many diseases, in which it extends in general
over the whole muscular system, and in which the patients are, as
they say, fatigued and wearied, as after a long march. This sensation
appears to depend on the peculiar kind of animal sensibility of the
muscles, a sensibility which the other agents do not develop, and
which the permanency of contraction renders here very apparent. Thus
the fibrous system, sensible only to the means of distension which act
upon it, does not receive a painful influence from the other agents of
irritation. Observe that this painful sensation, which a too prolonged
motion produces in the muscles, is intended by nature to warn the
animal to place limits to it, without which the consequences would
be serious. Thus the peculiar sensation which arises from distended
ligaments, is designed to make the animal limit their extension.
Observe how each organ has its peculiar kind of sensibility; how
false an idea we should have of the existence of this property, if we
judged of it only from mechanical and chemical agents, and observe
particularly how nature accommodates to the uses of each organ its kind
of animal sensibility.

In phlegmasia of the peculiar muscular texture, the animal sensibility
is very often raised to a very great height; the least touch on the
skin becomes painful; the patient can hardly bear the weight of the
clothes, and frequently the least jar produces in the limbs the most
acute pains. But in general these pains are wholly different from the
painful sensation which we call lassitude; thus the pain of a ligament
stretched in a sound state, is not the same as that which arises from
the inflammation of a ligament or any other fibrous organ.

I would add to what I have said above upon this sensation, that some
organs are fatigued like the muscles, from too long continuance of
their functions; for example, the eyes by the contact of light, the
ears by that of sounds, the brain by thinking, &c. and in general all
the organs of animal life; it is even this general lassitude which
brings on sleep, as I have proved in my Researches upon Life. But
observe that the sensation which the eye, the ear, the brain and all
the external organs produce when thus fatigued is not the same as that
which arises from the over-exertion of the muscles; another proof of
the peculiar kind of their sensibility, and in general of that of every
living part.


_Animal Contractility._

This animal property, upon which all the phenomena of locomotion
and voice depend, which assists those of the internal and external
functions, has its seat exclusively in the animal muscular system;
it is this which distinguishes it from the organic, and from all
the others. It consists in the faculty of moving under the cerebral
influence, whether the will or other causes produce this influence.
The animal contractility has then, like the sensibility of the same
species, a peculiar character, differing from the two organic
contractilities, a character which consists in this, that its exercise
is not concentrated in the organ which is moved, but that it requires
also the action of the brain and the nerves. The brain is the principle
from which, if we may so say, this property goes, as it is that to
which all the sensations come; the cerebral nerves are the agents
which transmit it, as they are, though in an opposite direction, the
conductors of the sensitive phenomena. Whence it follows, that in order
to understand this property well, it is necessary to examine it in the
brain, in the nerves and in the muscle itself.


_Animal Contractility considered in the Brain._

Every thing in the phenomena of animal contractility proclaims the
influence of the brain.

In the ordinary state if more blood is carried to this organ, as in
anger; if opium, taken in a moderate dose, excites it slightly; if
wine produces the same effect, the muscular action increases in energy
in proportion as that of the brain is thus increased. If terror by
retarding the pulse, by diminishing the force of the heart, and even
the quantity of blood sent to the brain, strikes it with atony; if
the different narcotics, carried to excess, produce the same effect;
if wine prevents its action by its too great quantity, then observe
these muscles languish in their motion and experience even a remarkable
intermission. If the brain is wholly engrossed in its relations with
the senses, or in its intellectual functions, it, if we may so say,
forgets the muscles; these remain inactive; the man who looks or hears
with attention, does not move; neither does he who contemplates,
meditates and reflects. The phenomena of ecstasy, the history of the
studies of philosophers, often present us with this important fact,
this muscular inertia, the principle of which is in the distraction of
the cerebral influence, which does not increase in other functions,
only by diminishing in locomotion.

In diseases, all the causes which act strongly on the brain, re-act
suddenly on the animal muscular system; now this reaction is manifested
by two opposite states, by paralysis and by convulsions. The first is
the indication of diminished energy, the second that of increased; one
takes place in compressions from pus, effused blood, bones driven below
their natural level, and from the consequences of apoplexy; it is seen
in the attack of most hemiplegias, a sudden attack in which the patient
falls down, loses all consciousness and has all the signs of a cerebral
lesion. This lesion disappears, but its effect remains, and this effect
is the immobility of a part of the muscular system. The other state or
the convulsive, arises from the various irritations of the cerebral
organ from osseous fragments driven into its substance, from its own
inflammation or that of its membranes, from different tumours of which
it may be the seat, from organic lesions that it may have, lesions
which I have rarely observed in the adult, but which infancy sometimes
exhibits, and from the causes even of compressions; for oftentimes we
see this convulsive state existing at the same time with different
effusions, with hydrocephalus, &c.

The state of the animal muscular system is truly the thermometer of the
state of the brain; the degree of its movements indicates the degree of
energy of this organ. Those who attend in a lunatic hospital have often
occasion to consult this thermometer. At the side of a furious patient,
whose muscular power is doubled, or even trebled, you see a man all
whose motions languish in a remarkable inertia. A thousand different
degrees are observed in these motions; now these degrees do not depend
upon the muscles; the most furious madman is often he whose very
delicate external forms indicate the weakest muscular constitution; as
the most perfect automaton is sometimes he whose muscles are the most
powerfully developed. The muscles are to the brain what the arteries
are to the heart. The physician learns by these vessels the state of
the central organ of circulation which communicates impulse to them; by
the muscles of animal life, he learns the state of the central organ of
this life. Observe patients in many important fevers; in the morning
there is prostration, in the evening you find an extreme agitation in
the muscles. Now what is the seat of this revolution? It is not the
muscles, but it is the brain. There has been a translation to the head,
as it is commonly called.

If from the bed of the sick we go to the laboratory of the
physiologist, we shall see experiments in perfect accordance with
the preceding observations. The ligature of all the arteries that go
to the brain, interrupts immediately the movements of this organ,
movements necessary to its action, and produces a sudden cessation
of voluntary motion, and afterwards death. By injecting through the
carotid and towards the head, ink, solutions of neutral salts, acids,
substances whose contact is fatal to cerebral action, I have always
seen the animal perish with previous convulsive motions. The injection
of water does not produce this effect; it can with impunity to the life
of the brain be introduced into the arterial blood, if it is injected
moderately; but pushed with force, you will irritate extremely this
organ, and in an instant the animal is seized with violent agitations;
moderate the force, rest succeeds. I have already related this
experiment elsewhere. If we lay bare the cephalic mass, and irritate
it with a mechanical or chemical agent, &c. in an instant the animal
muscular system is brought into action. It is however to be observed
that in these experiments the convexity of the organ appears to be much
less connected with the motions, than its base. The irritation confined
to the cortical substance, to the superficial layers of the medullary,
is almost nothing; it is not till we arrive at the inferior layers,
that the convulsions come on. I have wished to try many times to
ascertain with precision the place where the irritation becomes a cause
of convulsion; but this has always appeared to me very difficult, and
the results have been infinitely various. I believe that we can hardly
establish any thing more than a general result, viz. that the nearer we
approach in the experiments the annular protuberance, and in general
the cerebral base, the more apparent are the convulsive phenomena; they
are so much the less as we remove from them, they are nothing on the
convex surface. Observe that it is on the side of its base, that is to
say, on the side of its essential part, that the brain receives the
numerous vessels which carry to it excitement and life, whether by the
motion which they communicate to it, or by the nature of the red blood
which they carry to it, as my experiments published the year passed
have, I think, demonstrated.

Add to these experiments those of the artificial commotions. The
muscles of the ox vacillate, and are unable to support themselves,
the instant the blow is struck. At other times animals expire, their
limbs convulsively agitated from a blow given on the occiput; rabbits
often exhibit this phenomenon. Pigeons die with convulsive motions of
the wings. Irregular agitations arising from an irregular influx of
the power of the brain always precede the instant of death, which the
commotion has produced.

Let us conclude from all these experiments and the observations that
precede them, that the action of the animal muscular system is always
essentially connected with the state of the brain, and that when this
action is increased or diminished there is almost always an increase or
diminution of the cerebral action.

Let us not however exaggerate the relation which connects the muscular
to the cerebral phenomena; observation would prove us incorrect.
There are various examples of aqueous, sanguineous and even purulent
congestions in the brain, without having produced any alteration in
muscular motion. Different tumours and defects of conformation have
occasioned disturbance of the intellectual functions, without affecting
those of the muscles; how many times is the brain disordered in
various species of alienations; how many times do the understanding,
memory, attention and imagination indicate these derangements by
their irregular aberrations, without their being felt by the muscular
system. Is there not often an alteration of the external sensation,
without an alteration of motion? In general the brain has three great
functions. 1st. It receives the impressions from the external senses;
it is in this relation the seat of perception. 2d. It is the principle
and the centre of the voluntary motions, which are not exerted but
by its influence. 3d. The intellectual phenomena are essentially
connected with the regularity of its life; it is as it were the seat of
them. Now it can be deranged as to one of these functions, and remain
sound as to the others; it can be a regular principle of the motions,
and an irregular centre of the phenomena of the understanding; not
communicating with external objects by the senses, and determining
motions, or presiding over intellectual functions, as happens in sleep
which is disturbed by dreams, &c.

From what has been said we can understand why acephalous fœtuses
cannot live out of the womb of the mother. As animal life is nothing
in the fœtus, as respiration does not take place, as the functions are
limited to the great circulation, to the secretions, exhalations and
nutrition, the acephalous fœtuses can live in the womb of the mother,
and acquire a very considerable size; but at birth they cannot breathe,
the intercostals and diaphragm being unable to act. The gastric viscera
receives no influence from their muscular parietes; all the limbs are
immoveable. Animal life, which commences in others at birth, cannot
commence in them, because they have not the centre of this life; they
have senses, but nothing to receive their impressions; muscles, but
nothing to make them move; they can continue to live but a little
while in themselves, without beginning to live from without. But as in
general it appears that when the infant quits the womb, the red blood
becomes necessary to it, that to have this, it must respire, and as
this function cannot commence, it loses the internal life which it had
in the womb of the mother. There are acephalous fœtuses which have at
the origin of the nerves a small medullary swelling; in others the
spinal marrow is larger. If these medullary swellings, if the spinal
marrow by its peculiar texture, supply the place of the brain, life
can continue, and it is in this way that we can explain some examples
of acephalous subjects that have lived a certain time. But certainly
an acephalous subject organized like ourselves, which has nothing to
supply the place of the brain, cannot live. Thus in almost all the
examples of these monsters, related by authors, and especially by
Haller, the death of the individual took place at its birth.


_Animal Contractility considered in the Nerves._

The brain, at a distance from almost all the muscles, communicates with
them by the nervous system, and by it transmits to them its influence;
now this communication is made in two ways. 1st. There are nerves which
go directly from the brain to the muscles of animal life. 2d. The
greatest number does not go from this organ itself, but from the spinal
marrow. Almost all the muscles of the neck, all those of the chest, the
abdomen and the extremities receive theirs from this last source. The
spinal marrow is, as it were, a general nerve, of which the others are
only divisions and principal branches.

All the lesions of this principal nerve are felt by the muscles that
it has under its influence; the compressions that it experiences from
a fracture of the vertebræ, from any displacement, from an effusion
of blood, serum, pus, &c. in the vertebral canal, the derangements
which take place from a violent blow received upon the whole region
of the spine, from a fall upon the loins, or on the superior part of
the sacrum, are followed by numbness and paralysis of the subjacent
muscles. Divide the spinal marrow, by introducing a scalpel into the
canal, immediately all motion ceases below the division. If you wish on
the contrary to produce convulsions, introduce a stilet into the canal;
irritate the marrow with it or by chemical agents placed on it, there
will be immediately agitation and convulsion in all the animal and
muscular system that is below.

The higher the lesion of the marrow is, the more dangerous is it.
In the lumbar region its influence extends only to the inferior
extremities, and the muscles of the pelvis; in the back it paralyzes
these muscles and those of the abdomen; now as these last contribute
indirectly to respiration, this function begins to be embarrassed; if
the lesion is above the dorsal region, it becomes still more painful,
because the intercostals lose their action; the diaphragm alone then
supports the respiratory phenomena, because the phrenic nerve still
receives and transmits the cerebral influence. But when the lesion
happens above the origin of this nerve, there is no more action of the
diaphragm, and no more contraction of the intercostal and abdominal
muscles; respiration ceases; from the same cause the circulation is
interrupted; the blood being no longer carried to the brain, the action
of this organ is annihilated. Hence why the luxations of the first
vertebra on the second are suddenly fatal, when the displacement is
very great; why judicious surgeons dare not sometimes run the hazard
of reduction, when these luxations are partial, for fear of rendering
them complete, and of thus seeing the patient, whom they attempted to
relieve, perish in their hands; why, when we wish to knock down an
animal, the blow should be given on the superior and posterior part
of the spine; and why a stilet plunged between the first and second
vertebræ immediately destroys life.

We see very distinctly the successive influence of the different parts
of the marrow on the muscles and on the general life, by introducing a
long piece of iron into the inferior part of the vertebral canal of an
animal, of a guinea pig for example, and carrying it up through this
canal to the cranium, through the spinal marrow which it tears. We
observe evidently as it ascends, at first convulsions of the inferior
extremities, then those of the abdominal muscles, then derangement of
respiration, then its cessation, then death which is the consequence of
it.

From all these facts, we cannot, I think, call in question the
influence of the spinal marrow upon motion, the principle of which it
receives from the brain and afterwards transmits it to the nerves.
These last carry this principle, which they have received, to the
muscles, either by means of the spinal marrow, as in almost all those
of the trunk and the extremities, or directly from the brain, as in
those of the face, the tongue, the eyes, &c. There are the same proofs
for this nervous influence, as for that of the preceding sensitive
organs. The tying, division or compression of a nerve paralyzes the
corresponding muscle. Irritate with any agent a nerve laid bare in an
animal, convulsive contractions are immediately seen in the muscle.
These experiments have been so often and so accurately repeated by many
authors, that I think it useless to go into details, which the reader
may find everywhere. Irritation continued some time upon one point
of the nerve destroys its influence upon the muscle, which remains
immoveable; but it is put in motion again, if the irritation is carried
to a lower part of the nerve. If we tie it, the motion ceases, if
irritation is made above the ligature, it returns when it is made
below, or when the ligature is removed.

I would remark that all the nerves of animal life do not appear to
be equally capable of transmitting to the muscles the different
irradiations of the brain. In fact whilst in diseases, in wounds of
the head, in our experiments, &c. the muscles of the extremities are
convulsed or paralyzed with great ease, those of the abdomen, the neck,
and especially the chest do not exhibit these phenomena, except when
the causes of excitement and debility are carried to the highest point.
Nothing is more frequent than to see the abdomen and the chest with
their ordinary degree of muscular contraction, whilst the extremities
or the face are agitated with convulsive motions. Examine most
hemiplegias; the mouth is twisted, the superior and inferior extremity
of one side become immoveable, and yet the pectoral and abdominal
motions continue. Those of the larynx are more easily interrupted
than these in paralysis; hence the different injuries of the voice.
We could make a scale of the susceptibility of the muscles to receive
the cerebral influence, or of the nerves to propagate it, for it is
difficult to determine to which of these two causes the phenomenon is
owing; we could, I say, make a scale, at the top of which should be
placed the muscles of the extremities, then those of the face, then
those of the larynx, afterwards those of the pelvis and the abdomen,
and finally the intercostals and diaphragm. These last become convulsed
and paralyzed with the most difficulty of all. Observe how this scale
is adapted to that of the functions. What would become of life, which
is always actually connected with the soundness of respiration, if
all the cerebral lesions were as easily felt by the diaphragm and the
intercostals, as by the muscles of the extremities? Paralysis in these
last only takes from the animal a means of communication with external
objects; in the others it interrupts immediately both internal and
external life.

The nervous influence is only propagated from the superior to the
inferior part, and never in an inverse direction. Cut a nerve in
two, its inferior part when irritated will make the subjacent
muscles contract; let them do what they will to excite the other, no
contraction is produced in the superior muscles; so the spinal marrow
divided transversely and pricked above and below, produces no sensible
effect but in the second direction. The nervous influence never extends
upward for motion, as it does for sensation.


_Animal Contractility considered in the Muscles._

The muscles essentially destined to receive the cerebral influence
by means of the nerves, have however an active part in their own
contraction. It is necessary that they should be entire to exercise
this property, and answer to the excitement of the brain. When any
lesion affects their texture, and it is no longer the same as usual,
the muscle remains immoveable or moves with irregularity, though
it receives a regular nervous influx. The following are various
circumstances relative to the muscle itself, which prevent or alter its
contractions.

1st. An inflamed muscle does not contract; the blood which then
infiltrates it and penetrates its fibres, their great excitement and
the increase of its organic forces, do not permit it to obey the
stimulus it receives. In angina, deglutition is as much interrupted
by the inaction of the muscles, as by the inflammation of the mucous
membrane. We know that the inflammation of the bladder is one cause of
the retention of urine; that of the diaphragm renders respiration very
painful, which the intercostals perform almost alone.

2d. Every thing which tends to weaken and relax the muscular texture,
as external blows, bruises, contusions, infiltrations of serum in
dropsical limbs, or distension from a subjacent tumour long continued,
alters, changes the nature of, and can even annihilate animal
contractility.

3d. Whenever the blood ceases to enter the muscles by the arteries,
these organs remain immoveable. Steno has observed, and I have always
seen, that in tying the aorta above its bifurcation which forms the
internal iliacs, paralysis of the inferior extremities immediately
comes on. We know that in the operation for aneurism, a numbness more
or less considerable almost always follows the ligature of the artery.
This numbness continues until the anastomoses supply the place of the
artery which no longer brings any fluid. The internal motion created in
the muscle by the entrance of the blood, is then a condition essential
to muscular contraction. Thus the habitual motion imparted to all the
other organs and especially to the brain, maintains their excitement
and their life.

4th. It is necessary in order to obey the cerebral influence that the
muscle should not only receive the shock of the blood, but also of
the red or arterial blood. Black blood cannot by its contact support
motion. A general weakness and the fall of the animal are the first
symptoms of asphyxia, a disease in which the black blood goes to all
the parts. I shall not here repeat the proofs of this assertion, which
appears to me to be amply demonstrated by my Researches upon the
Different Species of Death. I refer to my work upon this point.

5th. A fluid differing from the blood, water, oily and albuminous
fluids, and for a stronger reason acrid and irritating fluids, the
urine, solutions of the acids and the alkalis, &c. are not proper to
support muscular action; on the contrary they paralyze it; injected
into the crural arteries of a living animal instead of blood, which
is stopt above by a ligature, they weaken and even annihilate the
motions, as I have frequently satisfied myself. The result varies in
these experiments according to the fluid employed in making them; the
rapidity of the cessation of the motions is more or less striking; they
are either weakened or totally suspended; but there is always a very
great difference between that and the natural state.

6th. Does the contact of the different gases upon the muscles modify
their contractions? Since the publication of my Treatise upon the
Membranes, I have made no experiment upon this point. Those which are
contained in it present the following results; frogs and guinea pigs
rendered emphysematous by blowing air into the sub-cutaneous texture
which afterwards penetrates the cellular interstices, and comes
everywhere in contact with the muscular system, move almost the same
as usual. If oxygen is used, the motions of the emphysematous animals
are not accelerated; they are not diminished if we employ the carbonic
acid gas, hydrogen, &c. In general, all the artificial emphysemas that
I have made upon the two species mentioned, in order to have an example
in each class of animals with red and cold blood, and of those with red
and warm blood, succeeded very well, and did not appear to cause any
sensible embarrassment to the animal, which gradually got rid of it.
Emphysema with nitrous gas is constantly fatal; the contact of this gas
seems almost suddenly to strike the muscles with atony.

7th. If instead of blowing gas into the cellular texture of an animal,
we force in different fluid substances, they produce different effects
upon the muscles, according to their nature, and to their acrid,
soft, or styptic qualities. No injection produces a more sudden and
striking effect than that of opium dissolved in water, or than that of
its various preparations; when the muscles feel it in contact, their
motions cease, they fall as in paralysis.

In general I would observe that it is infinitely better to make the
experiments of the contact of the gases and the different fluids upon
the muscles, by blowing the first, and injecting the others into the
intermuscular texture of a living animal, than by drawing out a
muscle, and afterwards plunging it all alive into the one or the other;
or than laying a muscle bare, in order to direct upon it the current of
a gas, or to moisten it with a fluid, for the purpose of observing the
phenomena of the contact.

It follows from all that we have just said, 1st, that to answer to
the cerebral excitement by contracting, the muscle should be in
general in a state determined by the laws of its organization; that
out of this state it is not capable of contracting, or at least that
it does it feebly and irregularly; 2d, that the contact of different
foreign substances produces upon the muscle a very variable effect.
Moreover many causes besides those stated above, appear to me also
to alter the contractions, by acting directly upon the muscles, such
as mercury taken by friction for the venereal disease, the influence
of this metal, of copper and of lead, upon those who work in them,
the action of cold, that of certain fevers, &c. The muscular tremor
arising from these different causes, does not appear to arise from
the brain; this organ at least does not most commonly give any sign
of affection in this case; I confess however that in these different
species of tremors, it is not easy to distinguish that which belongs to
the peculiar affection of the muscle, from what arises from that of the
nerves; perhaps these are especially affected, but the brain certainly
does not participate.


_Causes which bring into action Animal Contractility._

We have just seen that in the natural state this property constantly
requires three actions, 1st, that of the brain; 2d, that of the nerves;
3d, that of the muscles; that it is from the brain that the principle
of motion goes which is propagated by the nerves, and which the muscles
receive. But it is necessary that some agent should excite the brain to
determine it to exert its influence. In fact, the animal contractility
being essentially intermittent in its exercise, so that each time
after it has been exerted it is suspended, it is necessary that a new
cause should place it again in activity; now this cause acts at first
upon the brain in the natural state.

I refer to two classes the causes that excite the brain in order to
produce animal contractility. In the first is the will, in the second
are all the impressions which this organ receives, and which are not
under the control of the mind.

The brain is only intermediate between the mind and the nerves, as the
nerves are between the muscles and the brain; the principle, which
wills, acts at first upon this organ, which afterwards re-acts. When
they are thus produced, our motions are sometimes precise and regular;
that is when the intellectual functions are sound, when the memory,
imagination and perception are clearly exerted, when the judgment
being correct, directs with regularity the acts of the will; sometimes
they are irregular and singular, it is when the intellectual functions
disturbed and agitated in various ways, produce a singular and
irregular volition, as in the various mental alienations, in dreams, in
the delirium of fevers, &c. But in all these cases, these are always
voluntary motions; they go from the immaterial principle that animates
us.

In the second class of causes which influence the brain, the animal
contractility becomes involuntary; it is exerted without the
participation of the intellectual principle, often even against its
will. Observe an animal whose brain is artificially irritated in
experiments; it tries to stiffen itself to prevent the contractions,
they take place in spite of it; prick a nerve in an operation, the
muscle contracts suddenly below, without the mind's participating in
this movement; the patient has not even a consciousness of it; he
has only that of the pain. When much blood flows to the brain in the
violence of inflammatory fevers, this organ excited by the fluid,
re-acts immediately upon the muscles, without the will's partaking
in it. All the phenomena of contraction and relaxation, arising from
different accidents which accompany wounds of the head, cerebral
inflammations, &c. are equally involuntary, although having their
seat in the muscles which the will habitually directs. These are the
different circumstances in which the action of any agent upon the brain
is direct and immediate, and in which there is a mechanical cause
applied to the brain.

In other circumstances the brain is only affected sympathetically. In
many acute affections what is called translation to the brain, does not
arise from more blood being carried to it; the pulse is not fuller,
the face is not more flushed; there are often even signs of languor
in the action of the vascular system. The brain is affected, like all
the other organs by sympathy, a happy word, which serves to veil our
ignorance in respect to the relations of organs to each other; the
brain is affected then like the heart, the liver, &c. Take for example
peripneumony; the lungs are then the organs that are essentially
injured, from this essential and local injury, arise many sympathetic
ones more or less severe. If the liver is sympathetically affected,
bilious symptoms are joined to the symptoms of the principal affection;
if it is the stomach then gastric symptoms are manifested. The heart is
always agitated; hence there is fever. When the sympathetic influence
extends to the brain, there is violent motion, convulsions, &c.; for,
as I have said, the state of the muscles is the index of the state of
this organ; now, in this last circumstance, the will has nothing to do
with the animal contractility in exercise; the patient cannot prevent
the convulsive agitation of his muscles; the sympathetic irritation of
the brain is stronger than the influence of the will. This example of
cerebral affection in peripneumony, though more rare than in many other
diseases, may however give us an idea of what takes place in all other
cases in which the muscles are convulsively agitated by the injury of
any organ, by that of the fibrous system distended, of the ligaments
and especially of the aponeuroses, by dentition, by violent pains in
the kidneys, in the salivary glands or the pancreas, occasioned by
a stone, by injuries of the diaphragm, the nerves, &c. In all these
cases, there is an affected point in the economy; from this point the
sympathetic irradiations go off, which especially reach the brain; this
irritated by them, enters into action and excites the muscles; their
contraction takes place and the will is a stranger to it.

See also how the passions which have their influence particularly over
the internal organs, which especially affect those placed around the
epigastric centre, the heart, the liver, the stomach, the spleen, &c.
imprint on our motions an impetuosity, which the will cannot make us
masters of. The internal organ affected re-acts upon the brain, this
excited stimulates the muscles; they contract, and the will is almost
nothing in this contraction. Observe the man, whom jealousy, hatred
or rage agitates to the greatest degree; all his movements follow
each other with an impetuosity which judgment reproves, but which the
will cannot moderate, so much does the influence of the sympathetic
affection of the brain predominate over that of the will. At other
times the passions exhibit an opposite phenomenon. They are marked
by a general weakness of all the muscular motions. In astonishment
accompanied with grief, or in that in which is mixed a lively joy, the
arms fall down as it is commonly expressed; the cerebral influx ceases
almost entirely, and yet it is not to the brain that the influence of
this passion is carried, it is to the epigastric centre, as is proved
by the sudden contraction which is felt there. One of the epigastric
organs has been affected; it has reacted upon the brain; this has been
interrupted in part in its functions; the muscles feel it and theirs
cease. In fear in which this phenomenon is observed, as the paleness
of the skin indicates the languor of the circulating system, it may
happen that the cerebral and muscular inaction arises in great measure
from this, that there is not received a sufficient impulse from the
heart, upon which the first influence of the passion is exerted, and
which by this influence is retarded in its motions. Fear, it is said,
takes away the legs, petrifies, &c.; these expressions, borrowed from
vulgar language, indicate the effect of this passion on the muscles;
but this effect is only secondary; the first influence has been upon
the heart, the second upon the brain; it is not till after the other
two that the muscles are affected. Hence how certain animals remain
immoveable at the sight of that which is about to seize them for its
prey.

It is also to the sympathetic influence of the internal organs upon
the brain, that should be attributed the motions of the fœtus, motions
which the will does not direct; for the will is but a result of the
intellectual phenomena; now these phenomena are nothing at this period
of life. The internal functions then very active, suppose a great
action in the liver, the heart, the spleen, &c.; now these organs
in that way influence efficaciously the brain, and this in its turn
puts the muscles in motion; so that the animal contractility is by no
means voluntary in the fœtus; it does not begin to become so until the
sensations have brought into action the phenomena of the understanding;
until then, they must be compared to all those of which we have spoken
above.

From all that has just been said, it will be easily understood, I
hope, how the animal contractility can be or not subjected to the
influence of the will. In both cases, the series of phenomena which it
requires is always the same; there is always excitement by the brain,
transmission by the nerves, execution by the muscles, or successive
inactivity of these three organs. The difference is only in the cause
which produces the cerebral excitement; now this cause can be, 1st,
the will; 2d, an irritation immediately applied; 3d, a sympathetic
irritation. It is essential to form precise and exact ideas concerning
this vital force which performs so great a part in the living economy.


_Duration of the Animal Contractility after Death._

The difference of the causes which act upon the brain in the animal
contractility, in order to determine it to excite the muscles, appears
particularly in a remarkable manner at the instant of death. Whatever
may be the way in which this happens, the intellectual functions are
always the first to cease; it is even to this that we especially
attach the idea of the absence of life. Whence it follows that the
first phenomenon of this absence must be the failure of the muscular
contraction subjected to the influence of the will, which is the result
of these intellectual functions. Every thing then remains immoveable
in the muscular system, if no other cause acts upon the brain or the
nerves; but these two organs are, yet for a long time, capable of
answering to the various excitements of stimuli. Stimulate in any
way the brain, the spinal marrow or the nerves of an animal recently
killed, in an instant its muscles convulsively contract; it is the
same phenomenon as that obtained during life from the same cause.
Often even immediately after death, this phenomenon is still more
apparent than during life; I have been frequently convinced of this in
my experiments. If during life we irritate any nerve, the contraction
oftentimes is almost nothing, because the will acting by the other
nerves upon the same muscle, or at least upon those of the limb,
produces contractions opposite to those which the irritation tends to
produce. I have many times observed that the galvanic phenomena are
also infinitely more easily produced an instant after death, even in
animals with red and warm blood, than during life; in this last case
often we can obtain hardly any result, because their influence is
counteracted by the cerebral influence arising from the will. When the
irritation is directly applied to the brain or the superior part of the
spine, it then surpasses the will; it is stronger in the living animal;
but on an insulated nerve, it is often inferior to it; not that the
will acts by the irritated nerve, its influence in it is arrested at
the place stimulated, but it exerts itself by the adjacent nerves.

It is to the susceptibility of the brain and nerves of still
transmitting the principle of motion after death, that must be
referred all the phenomena that are witnessed in the different kinds
of decapitation. Ducks, geese and other animals of this family move
their muscles with some regularity, after the head is taken off, in
running, jumping, &c. Some time after the punishment of the guillotine,
the inferior and superior extremities are still the seat of various
tremors; the muscles of the face are sometimes even contracted so as
to give to this part the expression of certain passions, an expression
incorrectly referred to the sensitive principle still left for some
time in the brain. The same phenomena were formerly observed in the
punishment that consisted in cutting off the head with an axe. During
the year past I have had a painful proof of these singular facts; a
guinea-pig, whose heart I had just removed, plunged deep into my finger
the four prominent teeth that distinguish this species. All these
phenomena are only the result of the irritation produced, either by the
cutting instrument, or by the air, upon the two divided extremities
of the marrow; this is so true, that by increasing the irritation by
a pricking, cutting instrument, &c. with a chemical agent applied to
these extremities, the motions are very much increased. Nothing is
more easy than to be convinced of this fact in an animal; I have many
times proved it in those who have been guillotined, upon whom I have
been allowed to make experiments for galvanic purposes. See how the
alternate motions of respiration can continue for some time, after the
brain has been destroyed, after a wound of the head in which its mass
has been crushed, after a luxation of the first vertebra, in which
the beginning of the spinal marrow has been compressed so as suddenly
to stop life, after the injection of a very irritating fluid by the
carotid, &c. &c.

In this duration of animal contractility after death, the muscles are
absolutely passive; they obey, as during life, the impulse they receive
from the nerves; it is this which distinguishes it essentially from the
duration of irritability, a property by which, after death as during
life, the muscle has in it the principle which makes it move.

The duration is greater or less according to the class of the animals;
those with red and cold blood keep this property longer than those with
red and warm blood; among these, the family of ducks are, as I have
said, remarkable for this phenomenon, which is much more rapidly lost
in the others and in quadrupeds. In the first class there are also
varieties among the reptiles, fishes, &c.

In general I have constantly observed that the animal contractility
ceases after death, first in the brain, then in the spinal marrow and
last in the nerves. When the muscles no longer move by irritating
the first of these organs, they contract by stimulating the others.
The irritated nerves can still communicate a motion, when the spinal
marrow, no longer exhibits this phenomenon. I have not observed that
the superior part of the nerve ceased sooner to transmit motion, than
the inferior. But what is remarkable is that certain nerves, under
the influence of the same irritation, make their muscles contract
more strongly than others; such for example is the phrenic. When all
the other muscles cease to be moveable by the artificial excitement
of their nerves, the diaphragm is still moved by this means. Whilst
experiments have but little effect elsewhere, they are in full force
upon this muscle; this is the more remarkable, as during life this is
precisely the one which is the least affected by the state of the brain
and the spinal marrow; paralysis and convulsions hardly ever affect it,
as we have seen.

Besides, in thus comparing the duration of animal contractility, the
same stimulant should always be employed; for the effects are more or
less evident according to those which we use. When the whole brain and
the nerves are no longer sensible to mechanical or chemical agents,
they still powerfully obey galvanic impulses. The irritation of the
metals is of all the means at present known, the most efficacious in
perpetuating animal contractility some time after death.


_Organic Properties._

Organic sensibility is the manifest portion of the muscles of which
we are treating; constantly brought into action in them by nutrition,
absorption and exhalation, it becomes still more apparent, when we
irritate muscles that are laid bare; they feel this irritation, and
the motion, of which we shall speak hereafter, is the result of this
feeling which is centred in the muscle, and which is not referable to
the brain.

Insensible organic contractility is the attribute of this muscular
system, as of all the others.

The sensible organic contractility is very evident in it. If we lay
bare a muscle in a living animal, and irritate it with any agent,
it curls up, contracts and is agitated. A detached muscular portion
exhibits for some instants the same phenomenon.

Every thing is irritating to the naked muscle, the air, water, neutral
salts, the acids, the alkalis, the earths, metals, animal and
vegetable substances, &c. The mere contact is sufficient to produce
contraction. Yet besides this contact, there is something also which
depends upon the nature of the stimuli, and which makes the intensity
of the contractions vary. A powder of wood, coal, metal, &c. sprinkled
upon the muscles of a frog, produce but slight motions in it; pour on
it a neutral salt in powder, the marine salt for example, immediately
irregular agitations, and a thousand different oscillations are
manifested. Each body is by its nature capable of irritating the
muscles differently, as according to individuals, ages, temperaments,
seasons, climates, &c. the muscles are capable of answering differently
to excitements made upon them.

It is not necessary to irritate the whole of a muscle to produce its
contraction; two or three fibres only being pricked bring into action
all the others. Often even when we make these experiments on a living
animal, the contraction is communicated from one muscle to another. In
general I have constantly observed that during life these experiments
are less easy, and give results much more various, as we have already
stated with regard to animal contractility. Lay bare a muscle, irritate
it at many different times; sometimes it does not give the least sign
of contractility; sometimes it moves with force; this varies from one
instant to another. Whereas if it is upon an animal recently killed
that the experiments are made, the results are always nearly the same
in a given time, with the difference however of the weakness which the
contractions have in proportion to the length of time after death. It
never happens that you see a muscle immoveable under stimuli, which is
not rare in a living animal. This essential difference which authors
have not sufficiently pointed out, and which I have frequently proved
upon different animals, arises from this, that during life, the effects
of the nervous influence counteract those of the stimuli; for example,
if an animal extends with force his thigh by the posterior muscles,
we may in vain irritate the anterior ones, we cannot produce flexion
by this irritation. The cerebral excitement in the extensors being
stronger than the mechanical excitement in the flexors, triumphs. Often
when we apply the stimulant, the brain acts with force upon the muscle,
the effect is then much superior to the excitement we have applied. We
are astonished; but the astonishment ceases, if we recollect that there
is a concurrence of two excitements, of that of the external agent and
of that of the brain. In general, those who have made experiments, have
not paid sufficient attention to this concurrence of the two forces in
a living animal.

In order to estimate correctly the sensible organic contractility, it
is necessary to destroy the animal contractility. So long as these two
clash, interrupt and counterbalance each other, we cannot properly
estimate them, and determine what belongs to each and what is common
to both. Now we destroy animal contractility in the living subject, by
cutting all the nerves of a muscle or an extremity, which then become
paralyzed. The brain can no longer act upon them, and the results we
obtain from stimuli, belong to the sensible organic contractility.

The duration of this last property, after the experiment I mentioned,
proves completely that the nerves are wholly foreign to it, that it
resides essentially in the muscular texture, that it is, as Haller
said, inherent in it. Thus whilst in the different paralyses the
muscles lose the power of obeying the cerebral influence, or rather
this influence becomes nothing, they preserve that of contracting in an
evident manner when stimulated.

This contraction of the muscles of animal life by stimulants, appears
under two very different modes. 1st. The whole of the muscle can
contract and shorten so as to approximate the two points of insertion.
This happens in general when death is recent, when the muscle is still
fully possessed of life. 2d. There are oftentimes numerous oscillations
of the fibres; all are in action at the same time; now this action is
not a contraction, but a real vibration, a fluttering, which has not
a sensible effect upon the whole of the muscle, which not contracting
cannot approximate its moveable points. When life is about abandoning
entirely the muscle, it is thus that it moves. The diversity of the
stimuli occasions also this double mode of contraction. Carry a
scalpel over a living muscle, a contraction of the whole will be the
consequence; afterwards sprinkle the same muscle with a neutral salt,
sometimes there is an analogous contraction; but frequently there are
only oscillations, vibrations similar to those of a muscle which life
abandons.

During the life of the animal, its sensible organic contractility is
rarely in action, because the muscles have not agents that act upon
them in a sensible manner at least. Why then is this property so
developed in them? I cannot determine.

All the muscles do not possess it to the same degree; the diaphragm
and the intercostals are the most irritable; they are also those whose
organic contractility is the most permanent after death. Observe that
this contrasts, like their susceptibility to receive the nervous
influence by the irritation of their nerves, especially of the phrenic,
with the little disposition they have to feel, during life, convulsions
or paralysis. After them I think that the temporal, the masseter,
the buccinator, &c. are the most irritable. There is certainly as
it respects irritability a great difference between them and the
muscles of the extremities, which are all nearly equally susceptible
to the effect of stimulants. Besides, it is only by a great number of
experiments that we can establish general data; for nothing is more
frequent than to find inequalities between two analogous muscles, and
even between the corresponding ones of the two sides of the body.


_Sympathies._

The animal muscular system performs a very important part in the
sympathies. We see it very frequently agitated with irregular motions
in the different affections of our organs, especially in infancy when
every lively impression made upon any organ, is almost always followed
by spasmodic and convulsive motions in the muscles of animal life.
Observe in fact that it is the vital property predominant in this
system, that is to say the animal contractility, that is most often
brought sympathetically into action in it, by the influences that the
organs exert upon each other.

In general it appears that when the animal sensibility is strongly
developed in an organ, this system tends immediately to contract. The
acute pains that stones occasion in the kidneys, in the ureter and
even the urethra, distensions of the ligaments, of the aponeuroses,
dentition, surgical operations in which the patient has suffered much,
&c. produce very numerous and frequent sympathetic convulsions. I
know that there are very severe pains without sympathetic convulsive
motions; but it is very rare that you see convulsive motions of this
nature, without the organ, from which these sympathetic irradiations
go, is very powerfully affected, and the seat of great animal
sensibility.

Observe on the contrary that most of the sympathies which develop to a
great degree in any part, insensible organic contractility, or sensible
organic contractility, are not marked by these acute pains in the
affected organ from which the excitement goes; for example, sweats,
sympathetic secretions, intestinal and gastric contractions are rarely
produced by affections of the character of those from which arise the
sympathies of animal contractility.

The brain is always first affected in this last species of sympathies
in which the muscles are, as it were, passive, as we have already
seen, and in which they are made to obey the impulse they receive. The
affected organ acts at first upon the brain, then this re-acts upon the
muscles.

Authors have considered sympathies in too loose a manner. Some have
admitted, others have rejected the intermediate office of the brain;
some have not pronounced upon it. All would be agreed, if instead
of attempting to resolve the question in a general manner, they had
distinguished the sympathies according to the vital forces, of which
they are only aberrations and irregular developments; they would have
seen, that in the animal sympathies of contractility, the cerebral
action is essential; for we cannot conceive of any contractility of
this species, without the double influence, nervous and cerebral,
upon the muscles; that on the contrary, in the organic sympathies of
contractility, the action of the brain is nothing; the affected organ
acts directly and without any thing intermediate upon that which
contracts sympathetically. When the heart, the stomach, the intestines,
&c. move, when the parotid and other glands increase their action by
the sympathetic influence of an affected organ, certainly this organ
does not act first upon the brain; for it would then be necessary that
this should re-act upon those that contract; now it would not be able
to influence them except by the nerves, since it is only by these that
it is united to them; but all experiments and all facts prove as we
shall see, that the brain has not by this means any influence over the
organs with involuntary motions; then the action is direct and there is
nothing intermediate. There are sympathetic motions like the natural
ones; the sensible and insensible contractilities are constantly
brought into action by a direct stimulus applied to the organ, whilst
that the animal contractility is never exercised but by the cerebral
stimulant, which itself requires a cause, either sympathetic or
direct, in order to act upon the muscles.

Next to animal contractility, the sensibility of the same nature is
the most often brought sympathetically into action in the animal
muscular system. The lassitude, wandering pains, sensation of weight
and stretchings that are felt in the limbs in the beginning of many
diseases, are phenomena purely sympathetic, in which this property
enters into action in the muscles. At advanced periods of many other
affections, these sympathetic troubles are also very remarkable, but
less in general than at the beginning.

The organic properties are for the most part rarely sympathetically in
action in the species of muscles of which we are treating. Besides, if
they are so, we can hardly judge of it, because no sign points it out
to us. The sweat in the skin, the secreted fluids in the glands, the
fluids exhaled upon many of the surfaces, are general results which
indicate to us the sympathetic derangements of the organic sensibility
and of the insensible contractility of the same species. In the
muscles, we have not the same means of knowing these alterations.


_Characters of the Vital Properties._

From what we have thus far said, upon the muscular properties and
sympathies, it is easily seen that the vital activity must be in
general much greater in the muscles than in the organs previously
examined in this volume; thus all their affections begin to take
a peculiar character that distinguishes them from those of these
organs; they are much more prompt and rapid. Yet let us remark that
all the alterations of function which they exhibit, cannot assist us
in estimating this vital activity. In fact, many of these alterations
do not reside essentially in the muscular texture, their cause is not
there; such are for example all the convulsive motions in which, as we
have seen, the muscles act by obeying, but have not the principle of
action in them. They are then the indices of cerebral alterations; thus
the arteries, which exhibit such numerous varieties in the state of the
pulse, are as it were only passive, and serve most frequently merely
to indicate the state of the heart by their motion, whilst the veins,
which have not at the origin of their circulation an analogous agent of
impulse, very rarely exhibit varieties, though however their texture
may have as great vital forces, and its life be as active or more so,
than that of the arteries.

One proof that the texture of the muscle is less often altered than it
at first seems to be in considering the frequency of the affections
of these organs, is the infrequency of their organic lesions. These
lesions are even less common in them than in the bones. We do not see
in them those schirri, swellings, changes of texture in a word, which
are so commonly met with in the other organs. Among the great number
of subjects that I have had occasion to dissect or to have dissected,
I do not recollect to have seen in the muscles of animal life other
alterations than those of their cohesion, their density and their
colour. It is a phenomenon that approximates them to those of organic
life, in which we rarely meet with changes of texture, as the heart,
the stomach, &c. are examples.

The muscular texture of animal life rarely suppurates; thus but little
is known of its mode of suppuration. In general, it appears that
inflammation terminates in it almost always by resolution. Induration,
gangrene and suppuration, three terminations that this affection often
makes in the other parts, are unknown to this in the greatest number of
cases.


ARTICLE FOURTH.

PHENOMENA OF THE ACTION OF THE MUSCULAR SYSTEM OF ANIMAL LIFE.

Thus far we have spoken of muscular mobility, abstractedly from the
phenomena that it exhibits in the muscles, when it is in exercise in
them. These phenomena are now to be considered. They relate especially
to contraction, which is the essentially active state of the muscle,
relaxation being a state purely passive. We shall easily understand
the phenomena of this, when those of the other of which they are the
reverse are known to us.


I. _Force of the Muscular Contraction._

The force of the contraction of the muscles of animal life varies
much, according as it is brought into action by stimulants, or by the
cerebral action.

Every irritation made upon a muscle laid bare produces only a brisk,
rapid motion, but generally not very powerful. I have frequently
satisfied myself in my experiments that it is impossible to approximate
even at a great distance by this means, the great energy which
the brain communicates to the muscles of animal life. The organic
muscular system which stimuli directly applied put principally in
motion, never has exacerbations of force corresponding to those
which the animal contractility exhibits in so great a degree under
certain circumstances. It is then especially when the muscles move
in virtue of this last property, that the force of their contraction
must be considered. Now this contraction can, as we have seen, be
produced, 1st, by stimulating the brain in experiments; 2d, when
its excitement takes place in the natural state by the will, or by
sympathy. In the first case, the force of the contraction is never
very powerful, whatever may be the stimulant employed, either upon
the brain, or the nerves laid bare. I have uniformly observed a very
rapid convulsive motion, analogous to that produced by exciting the
muscles themselves, but never as strong as that which is the result of
vital action. Notwithstanding what some physiologists have written, we
can never by irritating the nerves of the flexors impart to them an
energy comparable to that which the will can give them. Irritate for
example the sciatic nerve in an inferior extremity which has just been
amputated, the toes will never bend with the force which they do in
certain cases in the natural state. I have twice made this experiment
in amputations performed by Desault. Unacquainted then with physiology,
I was much struck with this phenomenon.

In the cerebral excitement and in that of the spinal marrow, we cannot
so well appreciate the force of the contractions which result from
it, as when we stimulate an insulated nerve; in fact, all the system
entering then into convulsive action, the extensors destroy in part
the effort of the flexors and vice versa. The muscles simultaneously
in action, counterbalance, interfere with and injure each other. The
stimulant which gives the greatest force to the contractions, has
always appeared to me to be galvanism.

In the living state, the force of muscular contraction depends on two
causes; 1st, on the muscle; 2d, on the brain. These two causes are in a
variable proportion; it is necessary to consider them separately.

Under an equal cerebral influence, a muscle well nourished, which
appears distinctly through the integuments, and has very large fibres,
will contract much more strongly than that which is delicate, slender,
with loose, pale, small fibres, and which makes but a slight prominence
under the integuments. In our ordinary manner of considering muscular
force, it is to this state of the muscles that we especially attend.
The statues which exhibit strength and vigour, have always as an
attribute a powerful development of the muscular forms. When the brain
acts upon these muscles with energy they are capable of extraordinary
motions. I shall not relate examples of the astonishing efforts of
which they are susceptible. Haller and others have cited many of them,
either in the muscles of the back in carrying burdens, or in the
muscles of the superior extremities in raising great weights, or in the
inferior extremities in leaping or in order to preserve attitudes which
suppose enormous resistances to be overcome.

It is especially the cerebral influence that increases much the force
of muscular contraction. The will can raise this force very high; but
the different excitements that are foreign to it, raise it infinitely
more. We know the force that a man acquires in anger, that of maniacs,
of persons in the cerebral excitement of a fever, &c. In all these
cases the impulse communicated by the brain, is sometimes such, that
the most delicate muscles of the feeblest woman surpass in energy those
of the strongest man in the ordinary state.

The force of muscular contraction is then in a ratio compounded of the
force of the organization of the texture of the muscles, and of the
force of the cerebral excitement. If both are slight, the motions are
almost nothing; if both are at the highest degree, it is difficult to
conceive how far the effects may go which result from them; a maniac
with thick and strong muscles is capable of efforts that we should
in vain attempt to calculate. If the nervous force is very powerful,
and the muscular texture feeble, or if an inverse state exists, the
phenomena of contraction are less. In general nature has almost always
united these two things in this last manner. Women and children who
have a weak fleshy texture, have a very great nervous mobility; men
on the contrary, those especially with athletic forms, whose nervous
systems are less easily excited, receive more rarely the causes of a
strong influence upon their muscles.

Whatever may be the point of view in which we consider the force of
the contractions of the muscular system of animal life, it is always
very great in proportion to the effect which results from these
contractions. Nature in the economy follows a law the reverse of that
of the motion of our common machines, the great advantage of which
is to increase the moving powers, to produce a great effect with a
small force. Here there is always a great expenditure of force for
a small effect, which is owing to the numerous causes that tend to
destroy the effect of this force. 1st. The muscles act almost always
upon a very unfavourable lever, upon that in which the power they
represent is nearer the point of support than the resistance. 2d. All
in contracting have to overcome the resistance of the antagonists. 3d.
As in each motion there is always a fixed point, the effort which,
after contraction, is carried upon this fixed point, is entirely lost.
4th. Various frictions injure also the motion. 5th. The obliquity
of the insertion of the muscles upon the bones, an obliquity that
approaches nearer a horizontal than a perpendicular direction, an
obliquity not less remarkable for the fleshy attachments upon the
tendon or aponeuroses, offers a double cause of weakness. All these and
many other reasons which we might with Borelli, who was the first to
make these important remarks upon muscular motion, add to them, prove
that the absolute or real force of the muscles is infinitely superior
to their effective force. Yet all are not so unfavourably arranged;
in some, as the solæus, the insertion is perpendicular to the bone;
in others, as the muscles which act upon the head, we observe that
they are powers of a lever of the first kind. In general, in order to
estimate the force of a separate muscle, the deltoid, for example, it
is necessary especially to have regard to the distance of its insertion
at the point of support, to the degree of opening of the angles formed
by the fleshy fibres upon the tendon, and afterwards by the tendon
upon the bone, and to the division of the forces between the fixed and
moveable points.

Some advantages seem to compensate in a slight degree in certain
muscles for their bad arrangement as to the power of motion; such are,
1st, the sesamoids, the patella, the different eminences of insertion,
the enlargement of the large bones at their extremities, &c. which
remove the fibres to a distance from the moveable points; 2d, the
intermuscular fat, that which is in the neighbourhood of the muscles,
the fluid of synovial sheaths, which facilitate motions by lubricating
the surfaces that execute them; 3d, the aponeurotic expansions that
confine down the motions on the extremities; 4th, these motions
themselves, those of flexion for example, which, as they take place,
diminish the obliquity of the insertion of the flexors, and render it
even perpendicular, as has been well observed by a modern author.

Many calculations have been made upon the waste of muscular motion,
upon the effort of a muscle which contracts, compared with the effect
that results from it. They can never be precise because the vital
forces vary to an infinite degree, because they are not the same in
two individuals and because the cerebral influence and the force of
muscular organization are never in constant proportion in the same
subject. It is a peculiarity of the vital phenomena to escape all
calculations, and to exhibit, like the forces from which they emanate,
a character of irregularity which distinguishes them essentially from
the physical phenomena. Let us conclude only from the preceding
observations, that the muscular effort carried to the highest point by
cerebral excitement, can produce astonishing effects, which suppose a
force of contraction hardly conceivable; such is the rupture of the
strong tendons, of the patella, the olecranon, &c.; such is also the
resistance often opposed to the enormous distensions that are used in
luxations, fractures, &c.


II. _Quickness of the Contractions._

The contractions should be considered under the relation of their
quickness as under that of their force.

1st. If it is by stimulants that they are produced, by laying bare a
muscle and acting directly upon it, they vary according to the state
of vitality of the muscle, and according to the body which stimulates.
In the first moments of the experiment, they succeed with rapidity and
are sometimes connected together with such quickness that the eye can
hardly follow them. As the muscle becomes weak, its contractions become
less prompt; and they cease at the end of some time. We can reanimate
them by employing a very active stimulant; the fibres finally become
insensible to this also.

2d. If it is by irritating the nerve that we make a voluntary muscle
contract, we produce a still greater quickness of contraction than by
stimulating the muscle itself. Running would be almost immeasurably
rapid, if each contraction that it requires was equal to those that we
thus obtain, especially when we act on the one hand on very sensitive
animals, and on the other with very active stimulants, galvanism
for example. Upon this subject I have made a remark, it is that the
quickness and the force of the contractions are not commonly greater if
we irritate at the same time all the nerves that go to a muscle, than
if we irritate but one.

3d. When it is the will that regulates the quickness of the muscular
contractions, this quickness has infinitely various degrees; but
there is always one beyond which we cannot go. This degree is not
the same for all men; there is even among them in this respect very
great differences, which are foreign to the force of organization of
the muscles; it is rare even that individuals with a very powerful
muscular system are the best runners. I do not know that we have yet
observed the exterior habit of the body which indicates the quickness
of the contractions, as there is one which denotes their force; it must
however exist. Animals are like men; the degree of quickness which
each can attain, is infinitely variable. I shall not cite examples of
rapid races, of analogous motions given by the superior extremities, as
those of the fingers in performing on certain instruments, the violin,
the flute, &c.; astonishing ones may be read of in many authors. I
would only remark, that there are but few motions which give us a
greater idea of this quickness, than the sudden and rapid contractions
which, in the inferior extremities, produce a leap, or that powerful
action of these extremities when we give a kick with the foot; which
in the superior serve for the projection of heavy bodies; which in
the same limbs assist to push the trunk back, when we support them
against a resisting point, and afterwards suddenly stretch them to
push this point forward, which not yielding, the motion rebounds upon
the trunk; which preside over the action of giving a blow of the hand;
which in the fingers produce the sudden motion, from which results
what is called a fillip, &c. &c. I confound all these motions almost
entirely analogous to leaping, and which differ from it only in the
more or less evident effects that they produce. Authors, it may be
observed, have not sufficiently established the resemblances between
these various sudden and rapid contractions; they have considered
leaping in too insulated a manner. But let us return. The degree of
rapidity of muscular contractions is greatly subordinate to exercise.
The habit of making certain muscles act renders them more quick in
their contraction; for example, walking which accustoms us to contract
alternately the extensors and the flexors of the lower extremities,
fits us wonderfully for swiftness in running. When any man practises
for a little time this last exercise, he soon attains the greatest
rapidity of which his muscular system is capable. On the contrary, the
motions of adduction and abduction being more rare in the ordinary
state, it requires a longer apprenticeship for dancers to learn to
carry their legs rapidly in and out, for the purpose of executing steps
in which they cross them alternately. In general, habit modifies much
more the quickness than the force of the contractions. Yet there is
always a limit which can never be passed, whatever may be the exercise
that we give to the muscles; this limit depends on the constitution;
each man is by it, a more or less active leaper and runner.


III. _Duration of the Contractions._

There is as it respects the duration of the contractions a remarkable
difference in the muscles, according as we excite these contractions
artificially or naturally.

When upon a living animal or one recently killed, we excite the muscle
itself, or we stimulate its nerves, the relaxation succeeds almost
suddenly the contraction; neither state is ever lasting, though we
continue for a long time the action of the stimulant; the effect which
it has produced is immediately exhausted. When galvanism, mechanical or
chemical agents are used in our experiments, the phenomenon is the same.

On the contrary, when the will directs the contraction, it can sustain
it for a very long time. The support of burthens, standing, &c. clearly
prove this fact. When even during life, a morbid irritation is directed
upon the nerves, the contraction can be very permanent, of which we
have terrible proofs in tetanus.

The permanence of the muscular contraction fatigues the muscle much
more than alternate relaxation and contraction. Hence why when we are
standing long, we contrive by turns to carry the weight of the body
more upon one limb than the other.


IV. _State of the Muscle in Contraction._

Muscles that contract exhibit different phenomena as follows:

1st. They evidently harden, as we may be convinced by placing the
hand on the masseter, the temporal or any other superficial muscle in
contraction.

2d. They increase in thickness; hence the greater prominence of all the
sub-cutaneous muscles when the body is in violent action. Sculptors
know this difference very well. A man at rest and a man in motion, have
in their statues an exterior wholly different.

3d. The muscles when they are not confined by the aponeuroses,
sometimes experience a slight displacement.

4th. They diminish in length, and thus the two points to which they are
fixed approximate.

5th. Their volume remains about the same. What they lose in length,
they nearly gain in thickness. Is the proportion very exact? Of what
consequence to us is this insulated question, to which, since the days
of Glisson, so much importance has have attached! it deserves none.

6th. The blood contained in the vessels of the muscles, especially in
the veins, is in part pressed out; we increase the flow of the blood
by the motions of the arm, the operation of bleeding proves both these
facts.

7th. Yet the muscle does not change colour; it is because it is not
the colouring portion of the blood circulating with it in the muscular
vessels that colours the muscles, but, as I have said, that which is
inherent in their texture and combined with their fibres; now this
combined colouring substance remains the same in relaxation and
contraction. The heart of the frog is pale when it contracts; but it is
because the blood it contains is evacuated and the transparency of its
parietes renders this phenomenon evident.

8th. In contracting, the muscles become the seat of many small
transverse wrinkles, sensible especially in the contractions of
oscillation, less apparent in those of the whole of the muscle, and
almost nothing, when a muscle being laid bare in a living animal,
contracts with a small degree of force.

9th. All authors consider contraction in too uniform a manner; they
have described the phenomena of it, as if in every case the muscle
contracted alike; but it is evident that there are numerous differences
in the state in which it then is. 1st. There is the slow and insensible
contraction produced by the contractility of texture, when we cut a
muscle or when its antagonist is paralyzed. 2d. The quick and sudden
contraction produced by the will, or by the excitement of a nerve, a
mode of motion that takes place most commonly either in the ordinary
state, or in convulsions. 3d. The species of oscillation of which I
have already spoken, and which affecting each fibre in a muscle, does
not yet produce any very sensible effect upon the whole, contracts
it a little, but scarcely approximates at all its moveable points;
this is the kind of motion which takes place in the tremors produced
by cold, by fear, by the beginning of a fit of intermittent fever,
&c. By laying bare a muscle in an animal that is made to shiver, we
see that this kind of contraction resembles precisely that which is
produced by pouring salt in powder upon a part of the muscular system.
Then, although there may be in all the muscles, an internal motion
infinitely more sensible than in the great contractions, yet the
limbs are displaced but little, there are hardly any motions of the
whole muscles, they are but slight jars. 4th. There are other modes
of contraction less sensible than these, but which however exhibit
differences. In general, to each species of motion of the muscle
is adapted a particular manner of contracting; if we make but few
experiments on living animals, we may easily be convinced how much the
most judicious authors have been mistaken upon this point.

Two modes of contraction are often combined; for example, when we cut
a muscle transversely in a living animal, there is at first a slow
contraction of the whole, produced by the contractility of texture,
then partial oscillations in all the divided fibres; now these
oscillations are foreign to the retraction which takes place without
them, often in the living animal and always in the dead body. So the
oscillations can be combined with the sudden contraction arising
from the nervous influence by the act of the will, or they may be
disconnected with it, as happens almost always when the animal is in
full life. We may be convinced of this last fact without recourse to
experiments, by placing the hand upon the masseter muscle or the biceps
of a thin person when they are contracting; we do not feel in them
through the skin any motion analogous to these oscillations.


V. _Motions imparted by the Muscle._

Every muscular motion is either simple or compound. Let us now speak of
the first; by it we shall understand the second.


_Simple Motion._

It must be considered, 1st, in the muscles with a straight direction;
2d, in those in a reflected one; 3d, in those in a circular one.

In the first, as in those of the extremities, the trunk, &c. if they
are of an elongated form, and as they terminate by a tendon, each
fibre contracting draws this tendon from its place; whence it follows
that all act together to bring it towards the centre of the muscle, but
at the same time each of them tends to give it another direction, and
in this respect they are antagonists. The common motion remains; the
opposite is destroyed.

Every effort of contraction in the long muscles is concentrated upon
a single point, the tendon. In most of the broad muscles, on the
contrary, the attachments being made at two sides by different points,
all the fibres do not contribute to the same end. Thus the different
parts of the same muscle can have very different and even opposite
uses; thus the inferior portion of the great serratus does not act like
the superior; often even the different portions of the same muscle do
not contract at the same time. In a long muscle, on the contrary, as
all the fibres contribute to produce the same effect, they always act
simultaneously.

To estimate the effect which a muscle in the straight direction
produces upon the bones in which it is inserted, different means
are employed. A very simple one appears to be that, which I believe
has never been mentioned. It consists in examining the direction
of the muscle from its fixed to its moveable point, and in taking
the inverse of this direction; this last is always the direction of
the motion. Do you wish to know how the anterior radial acts upon
the wrist; take it at its insertion at the condyle, then follow its
direction downwards and outwards; you will see that it carries the
hand upwards and inwards, that it bends it and places it a little in
adduction. The tibialis anticus directed downwards and inwards raises
the foot and carries it outwards. The anterior rectus of the thigh
going straight from the pelvis to the patella, raises the leg directly
up. All the other muscles will exhibit this arrangement. Whatever
may be the attachment of their fixed or moveable point, they always
act inversely to the supposed line of direction going from the first
point; and as each attachment can be alternately moveable or fixed, the
two bones which serve them are carried in an opposite direction; the
coraco-brachialis directed downwards and outwards from the shoulder
towards the arm, carries this last upwards and inwards; directed
from below upwards and from without inwards from the arm towards the
shoulder, it moves this downwards and outwards. By this general rule,
it is sufficient to see a muscle in a dead body, to pronounce upon its
uses.

When the whole of a broad muscle is united at a common point, as the
deltoid which having many points of attachment above, is fixed below in
a single tendon, the middle line of direction of all its fibres should
be taken to estimate its uses.

When a muscle is attached by its two extremities at many points, and
consequently the fibres that compose it, form many fasciculi with
different directions and insulated motions, the line of direction of
each fasciculus must be examined in order to estimate the action of
the muscle. It is thus that we should study that of the trapezius, the
great serratus, the rhomboid, &c.

In the muscles with reflected direction, as the great oblique of the
eye, the lateral peronei, the circumflexus, &c. the action of the
muscle should only be estimated by the point of reflection; thus the
great oblique carries the eye inwards, though its fleshy portion
contracts so as to carry the moveable point backwards.

The orbicular muscles, those placed around the lips, the eyes, the
anus, &c. have in general no fixed or moveable points; they are not
designed to approximate two parts to each other, but only to contract
the opening around which they are situated. The anus is shut by its
sphincter, when the excrements do not dilate it. The mouth remains
closed, when the depressors, the elevators or the abductors of the
lips are inactive. The eye is shut, when the elevator of the superior
eye-lid is relaxed. I would remark upon this subject that the inferior
eye-lid having no depressor, it is principally the other which
contributes to shut or open the eye; and as its muscle cannot be in
permanent contraction, the alterations of its relaxations produce those
continual winkings which take place when the eye is open; they are to
the eye what the alternate change of the weight of the body from one
leg to the other is in long standing without motion. At every instant
the muscle relaxes; the sphincter acts immediately; then it contracts
and distends the sphincter; winking then is a continual struggle
between the elevator of the eye-lid and the orbicularis. In sleep, it
is not by the contraction of this that the eye is shut; it is relaxed
like all the muscles; it is because the elevator is inactive, that the
eye-lid falls by its own weight upon the eye; it communicates as it
were the motion to the orbicularis that it shuts up, whilst, during
the day, it is the orbicularis on the contrary that communicates this
motion to it.


_Compound Motions._

There are but few motions in the economy that are simple, but few
muscles that can contract separately. Almost every sort of contraction
supposes another, and for this reason; the two points to which a muscle
is ordinarily attached are both capable of being moved; if one of
them was not fixed, both would then be put in motion when the muscle
contracted; thus in the contraction of its extensors, the leg if it
was not fixed would approach the foot as much as the foot approached
the leg; now it could not be fixed but by the muscles which act in an
opposite direction to the effect which the extensors tend to produce
upon it; then whenever the two attachments of a muscle are moveable,
the insulated motion of one of them supposes the contraction of
different muscles to fix the other.

It is only those muscles that are attached on one side to a fixed point
and on the other to a moveable one, like those of the eye, and most of
those of the face, that can move in an insulated manner, and without
requiring a motion in the other muscles. It should be remarked however
that in general the contractions destined to fix the point which should
be immoveable in the ordinary motions, are less than they at first
seem to be. In fact, in these ordinary motions, the point which moves
is always the most moveable, that which remains without motion is the
least so; for example, it requires a much greater effort in flexors
to bend the arm upon the fore-arm, than to bend the phalanges upon
the fore-arm, or the fore-arm upon the arm. By supposing their two
attachments moveable, the gemelli would act much more powerfully on
the foot than on the femur, &c. In the extremities, the superior point
is always more moveable than the inferior, now it is this which almost
always moves, the other being fixed; then as it offers more resistance
by its position, it requires less effort of the muscular powers to
retain it. It is only in violent motions, that the previous contraction
of the muscles destined to fix one of the points of insertion Is very
painful. This takes place on the chest when the trapezius, the great
serratus and the great pectoral contract powerfully; then all the other
muscles of this cavity contract strongly to dilate it, and thus offer
a broader and more fixed attachment to those muscles, which move the
shoulder in the support of burdens, or in any other analogous effort.
The diaphragm contracts also; hence hernias, the descents which take
place from a concussion in those motions which, at first view, have no
analogy with the abdominal cavity. When in a horizontal position of the
body we raise the head, the rectimuscles of the abdomen contract to
fix the chest, and present a solid point to the sterno-mastoideus, &c.

We call especially a compound motion that which two or more muscles,
acting upon the same point, contribute simultaneously to produce. In
this case, the moveable point follows the direction of neither muscle,
if there are two of them, but takes the diagonal of their direction.
It is thus that the eye is moved outwards and upwards, outwards and
downwards, &c.; that the head is depressed, that it is carried to
one side, and that the arm is applied to the trunk, &c. In general
nature has distributed muscles only in some principal directions
around a moveable point, for example around the eye, in those of
elevation, depression, adduction and abduction; the combination of
these simple motions produces the compound ones. If the adductor and
depressor contract equally, the eye will be carried exactly in a middle
direction; if one acts with more force than the other, it will be
carried a little nearer the other; so that the four muscles, by moving
separately, or two by two in an equal manner, carry the eye in eight
different directions. In all the intermediate directions, there is also
a simultaneous action of two muscles, but always a superiority in the
action of one of them. Thus almost all the motions of circumduction
operate.

When two opposite muscles contract, the moveable part is not moved;
they are perfect antagonists. When two muscles which contract at
the same time are placed in the same direction, there is no loss
of power; this is what takes place when the genio-hyoideus and the
mylo-hyoideus depress the jaw or elevate the os hyoides; these muscles
act completely together. But when two muscles are in part opposed and
in part in the same direction, as the sterno-mastoidei, one portion
of the forces is destroyed and the other remains. The action by which
the sterno-mastoidei tend to carry the head to the right or the left,
is nothing; that alone by which they direct it downwards produces its
effect which is double, considering the action of the two muscles,
which are thus at the same time acting together and antagonists.
Hence we see that this applies not only to the motion produced by the
contractility of texture, but also very often to those which the animal
contractility occasions.


VI. _Phenomena of the Relaxation of the Muscles._

When a muscle ceases to contract, it becomes the seat of phenomena
precisely opposite to the preceding, which it is sufficient to know in
order to understand these. The muscle becomes longer and softer; its
wrinkles disappear; it returns exactly to the state in which it was
found. It is needless to give in detail the series of these phenomena.

I would remark that in the state of relaxation of the muscles, the
parts often execute motions which are only owing to their weight; such
are the flexion forwards of the head in sleep, the fall of the fore-arm
and the arm in the same case. Then the weight is often opposed to the
limbs, remaining in their middle position, which are not supported. We
see particularly these phenomena in paralysis.


ARTICLE FIFTH.

DEVELOPMENT OF THE MUSCULAR SYSTEM OF ANIMAL LIFE.

The muscular system exhibits great differences, according as we examine
it before the completion of growth, or in the ages that follow that in
which this growth is terminated.


I. _State of the Muscular System in the Fœtus._

In the first month of the fœtus, this system is, like the others, a
mere mucous homogeneous mass, in which can be distinguished scarcely
any line of demarcation. Aponeuroses, muscles, tendons, &c. all have
the same appearance. Gradually the limits are established, the muscular
texture at first takes a deeper tinge, from the blood that enters it.
Yet this tinge is at first much less evident than in the adult; it
remains nearly the same till birth. If we make use of the bones as a
means of comparison, this becomes striking. In the adult the interior
of the bones is less red than the muscular texture; the difference is
remarkable. It is the contrary in the fœtus; much more blood penetrates
the already ossified portion of the bones, than the interior of the
muscles. Nature distributes the blood in an inverse manner at these two
periods of life in these two systems.

I presume that this phenomenon is principally owing to the kind of
inertia in which the muscles remain before birth. Observe in fact
that though some motions announce in the last months the presence of
the fœtus in the womb of the mother, yet these motions are infinitely
less than they are to be afterwards. The proof of this is the constant
semi-flexed position which the limbs and trunk have, and the small
space that there is to execute these motions in, especially in the last
periods in which the waters are wonderfully diminished. In the early
periods of pregnancy, though the space may be greater, by opening the
females of animals, we constantly find the fœtus drawn up upon itself,
and in an attitude almost immoveable.

Many respectable philosophers have found the muscles of the chick in
its shell much less irritable than after birth, either by ordinary
agents, or by galvanic influence. I have made the same experiment
upon small guinea-pigs that were never born, by irritating directly
their muscles, or by stimulating their nerves, their spinal marrow and
the brain. The nearer we approach the term of conception, the less
are the motions obtained. That which is especially remarkable is the
rapidity with which, when the fœtus is dead, the muscles lose their
irritability; the instant that extinguishes life seems to destroy
this property. In the latter periods that precede accouchement, it is
a little more permanent, and more susceptible of being brought into
action, but always less than after birth. We can hardly doubt then
that the motions are less at this age, though however they exist. We
shall see that the nutrition, size and redness of the muscles are in
general in the adult in proportion to the number of the motions they
perform; it is not then astonishing that less blood penetrates them in
the fœtus. Besides the nearer we approach the period of conception,
the less abundant is this fluid in them. I have had occasion to make
this remark on guinea-pigs killed at different periods of gestation. In
the early periods, the muscles of the small ones really resemble those
of frogs; white like them, they are marked with reddish lines, which
indicate the course of the vessels.

I presume also that the kind of blood which circulates at this age
in the arteries and which penetrates the muscles, is less proper to
support and develop their mobility. In fact it is the black blood that
then enters the muscles by the vessels. We know that in the adult,
whenever this blood circulates preternaturally in the arterial system,
life is altered, the muscular motion is weakened, and soon asphyxia
comes on. It is to the nature and the colour of the blood of the fœtus,
that must be attributed the livid and often deep tinge that its muscles
exhibit; for this is also a character that distinguishes them from
those of the adult. Not only their colour is less evident and they
are paler, but their tinge is wholly different; and this tinge has
uniformly the character of that of the fœtus before it has respired.

The muscles are slender, but little developed in the fœtus. Their
development is infinitely less than that of the muscles of organic
life. The size of the limbs arises especially from their sub-cutaneous
fat. When this fat is in small quantity, and we compare the limbs
with the trunk, they are much less in proportion than they will be
afterwards. In the fœtuses that have much cutaneous fat, from whom
we remove all the skin, we also see this disproportion of size. We
know that at this age all the cavities of muscular insertion, all the
apophyses destined to the same use, are almost nothing. The parietes
of the temporal fossa, for example, more curved outward, enlarge the
cerebral space, and contract that which the temporal muscle fills. This
is a small anatomical fact which is the consequence of a great law of
nutrition, viz. of the predominance of the nervous system to which the
brain belongs, over the animal muscular, in respect to development. Let
us remark that this predominance, whence arises at this age an evident
disproportion between the muscular and nervous systems, when compared
to what they will be afterwards, would alone prove that the muscles are
not, as has been said, a termination and expansion of the nerves; in
fact two species of organs whose development is inverse, cannot belong
to one and the same system.

Many authors have pretended that the fleshy portion was in proportion
much more developed in the fœtus than the tendinous, that this even
did not exist. I cannot imagine whence this opinion arose. It may be
conceived that they have thought that the aponeuroses of the limbs
were wanting in the first months; I have uniformly observed that they
have not then that white colour which characterizes them afterwards,
a colour that they only take when their fibres are developed; they
are transparent, like a serous membrane, and cannot at first sight
be perceived. But the tendons have a very evident white colour; we
distinguish them very well; they are quite as large and as long in
proportion as they will be afterwards.


II. _State of the Muscular System during Growth._

At birth, the muscular system of animal life experiences, like all the
others, a remarkable revolution. Until then black blood only penetrated
its arteries; then the red blood immediately enters them; for this
blood is formed when respiration takes place; now this takes place in
almost all its perfection at the very instant the fœtus leaves the womb
of the mother. We evidently see besides that the livid tinge of the
skin gives place almost immediately to a red colour, which arises from
this difference of the blood. This new fluid entering the muscles, is a
new cause of excitement, and consequently of motion. Add to this cause
the sudden increase of cerebral action. Till then, the brain penetrated
with black blood, was as in a kind of inertia, which was principally
owing also to the absence of sensations, as I have elsewhere proved.
Suddenly the red blood enters it; it stimulates it either by the
principles that it contains, or because it was different from that
which had penetrated it; for such is the nature of sensibility that it
is capable of being affected in an organ, merely because the stimulus
that is applied to it is new. Suddenly excited by the red blood, the
brain re-acts upon the muscles, and determines them to contract. This
cause, joined to the preceding, appears to me to be one of those which
have the most influence on the sudden disappearance of the kind of
inertia in which the fœtus was, or at least of the small degree of
motion that it performed, by the general agitation of its limbs, its
abdomen, chest, face, &c.; for immediately after birth all the muscles
are moved more or less strongly.

Let us not, however, exaggerate the influence of a cause which is
certainly not the only one; for example, the motions of the diaphragm
and the pectoral muscles, are certainly prior to the entrance of
the red blood in the brain, since their action is necessary to the
production of this red blood. These muscles enter into action, because
the excitement of the air on the whole exterior of the body, and on
the mucous membranes in contact with this fluid, stimulates the brain
which is the centre of all sensation. Moved by this excitement, this
organ re-acts upon the muscles, and begins to make them contract. The
contractions increase, when to this external and indirect excitement is
added the internal and direct excitement of which we have just spoken.
This second excitement is not absolutely necessary for the fœtus, for
we often see infants that remain livid some instants after birth, move
very well; but in general the motions are not so decided as when the
red colour of the skin indicates the entrance of the arterial blood,
which has undergone the influence of respiration.

The entrance of the red blood into the muscles does not give them
immediately the colour they will afterwards have. For some time after
birth, they have a deep tinge, as dissections clearly prove, because,
as I have said, their colour does not come from the colouring portion
circulating in their texture, but from that combined with this texture.
Now nutrition alone produces the combination; but this function takes
place gradually; it is truly a chronic function, in comparison with
exhalation, absorption, and the circulation, which are evidently rapid
in their progress.

As we advance in age, the muscles assume a redder tinge; more blood
penetrates them; they are nourished in proportion more than various
other organs. This is particularly remarkable in those of the lower
extremities. I would remark, however, that as long as growth continues,
it is especially upon the length and not upon the thickness of the
muscles, that the energy of nutrition is carried. Hence why they are
but slightly visible through the integuments and are scarcely at all
prominent; why their forms are rounder and more graceful, but less
masculine at this age. The exterior of a young man is in this respect
wholly different from that of the adult, by considering each, separate
from every cause that can have an influence upon their conformation.
The external appearance of the infant and the young man is in general
very analogous to that of woman.

Though we do not know so well the difference of the substances which
penetrate the muscles in the first years and in the adult age, as we
know it in the bones in which the addition of the phosphate of lime
to gelatine exhibits a very striking phenomenon, yet we cannot doubt
that these differences really exist. Treated by ebullition, combustion,
maceration, &c. the flesh of the fœtus does not give the same results
as that of the adult.

The broth made with the muscles of a young animal contains much more
gelatine, a substance which greatly predominates at this period of
life. It has less flavour than that of adult animals. The extractive
substance consequently appears to be less. A mawkish, nauseous taste
characterizes broths made of veal. The difference of the principles
they contain has an influence even upon the gastric organs, of which
they excite the contraction; they loosen the belly, as it is called, a
phenomenon unknown to common broths. It does not appear that the fibrin
is in as great a proportion in the muscles at this period of life; the
following considerations make me think so.

1st. Instead of this substance, Fourcroy has found in the blood of the
fœtus a soft texture, without consistence, and like gelatine; now the
blood appears to be the reservoir of fibrin. 2d. The force and energy
of the contractions are in general in proportion to the quantity of
this principle contained in the muscles; now this energy is small in
the first age. 3d. The muscles burn then, and crisp and contract less
than in the adult. I have even two or three times seen their texture,
when placed upon live coals, become puffed up like gelatine treated in
the same way.

In general it appears that this last substance occupies in the muscles
the place the fibrous system is afterwards to hold in them. Those who
frequent dissecting rooms, have observed, no doubt, that other things
being equal, the muscles of young subjects putrify less quickly than
most other substances, and that when they do, they give out a less
fetid odour. We know that broth made of veal turns sour more easily
than that made of beef. It is always whitish, and never has the deep
colour of the broth made with this last. It becomes like jelly much
more easily. Young and old roast meats exhibit also great differences.
Every kind of stewing either by the fire alone, or in any fluid, is
much quicker and easier in the first age. The gravy that is then
extracted from the muscles has a character wholly different, it is less
strong. The effects of maceration are also more rapid; we obtain sooner
that mucous pulp, to which the action of water finally reduces almost
all animal substances.


III. _State of the Muscular System after Growth._

After general growth is finished in length, our organs then increase
in thickness; and it is especially in the muscles that this phenomenon
is remarkable. To the slender and delicate body and round forms of the
youth and young man, succeeds a large, strong and thick body with well
developed forms. The muscles can be traced through the integuments,
eminences and depressions are observed in them; different depressed
lines serve as limits to various prominent ones. The animal muscular
system is then more prominent in a state of repose, than it is in youth
in its greatest motions. Painters and sculptors have studied more than
anatomists the different degrees of the development of the muscles.

The period when the hairs grow, when the genital organs begin to become
active, is principally that in which the muscles begin to become
prominent in man. In woman, this last period does not present a similar
phenomenon; the muscles preserve the original roundness, they scarcely
ever lose it. In this sex, the roundness of the limbs, their agreeable
forms, make a contrast with the kind of rudeness of those of man.

The increase in thickness in the muscles appears to be much more
in the fleshy than the tendinous portion, and especially than the
aponeurotic. The intermuscular aponeuroses principally do not appear
to grow in proportion to the fibres that are inserted into them; so
that these make a prominence, and at the place of the aponeurosis there
is a depression. This is what we see very well in muscles cut for
their insertions by many of these fibrous expansions, in the deltoid
in particular. Not only the prominence through the skin of the whole
of the muscle, makes the depressions evident that separate it from
the others, but each fleshy bundle has a prominence which a groove
separates; this, it is true, is only distinguishable upon thin subjects.

As the muscle grows in thickness, it increases in density. It becomes
firmer and more resisting. If we place for comparison the hand upon
two similar muscles of an adult and an infant, whilst they are in
contraction, we feel a sensible difference in their hardness. Weights
suspended for comparison to the muscles of the two ages, taken in the
dead bodies, prove the different degree of their resistance. The
muscular texture of adults yields more slowly to all re-agents.

The colour of the muscles continues to be red in the adult; but in
general, and all things being equal in respect to the causes that make
this colour vary, it begins to become of a less bright red after the
thirtieth year. It is usually in the last years of growth, and even
from the tenth to the twentieth, that the colour is the most brilliant.

In the adult this colour exhibits a very remarkable phenomenon. All men
have their muscles red, but hardly two have the same shade. Those who
have opened many dead bodies are easily convinced of this; a residence
at the dissecting rooms proves this assertion. A thousand causes have
an influence upon this colour; the temperament is the principal. The
external appearance of the muscles without the skin indicates by
their shades of colour the temperament, as well as the integuments
do. Diseases make this colour vary wonderfully. All those that have
a chronic progress alter it remarkably; it then becomes pale, dull,
&c. Dropsies whiten it, when they are of long standing. In general,
every thing that has upon the powers of life a slow and debilitating
influence, diminishes the brightness of it. Acute diseases, whatever
may be their nature, change it but little. Fevers with the greatest
prostration, if they suddenly produce death, leave it untouched,
because this colour can only change by nutrition; now as this function
is slow in its phenomena, it is but little affected by acute diseases;
it is only at the end of some time that it feels the affections
reigning in the economy.

I would observe that the varieties of colour that are seen in the
muscles of adults, even in the healthy state, distinguish them
especially from those of the fœtus, which have in general an uniform
paleness. This difference is owing to the fact, that in the first
age, we are not subject to the action of the numerous agents which
modify, in an infinitely variable manner in the after ages, the great
functions, and of course nutrition which is the end of them. It is in
these varieties of colour of the muscular system of the adult, that
we clearly distinguish that the blood circulating in the arteries is
wholly foreign to it; in fact it is uniform, and never partakes of
those varieties of colour whatever they may be.

Many circumstances in the adult make the muscular nutrition vary;
motion is the principal. The man who passes his life at rest is
remarkable for the small prominence of his muscles, especially if we
compare this prominence with that of the muscles of a man who takes
great exercise. Not only general motion exhibits this phenomenon,
but also local motion, as we see in the arms of bakers, the legs of
dancers, the backs of porters, &c.


IV. _State of the Muscular System in Old Age._

In old age, the texture of the muscles changes remarkably; it becomes
resisting and stiff; the teeth tear it with difficulty. This too great
density is injurious to its contractions, which can now only take place
slowly; the action of the brain becomes less upon the muscles; the
continuance of their motions is not as long; they are sooner fatigued.

I would remark that the density of the muscles should not be confounded
with their cohesion. The first arises from substances that enter into
the composition of the muscle. Cohesion on the contrary appears to be
owing to vital influence, the effect of which is preserved after death.
Dissect the muscles of a strong and vigorous adult; the fleshy mass is
firm; it keeps in its place; it supports itself, though the scalpel
may have removed from it every surrounding texture. On the contrary
in a body dead of a chronic disease, in a dropsical or phthisical
subject, the muscles are loose and cannot support themselves; the
relations are destroyed when the surrounding texture is removed. The
first subjects are much more suitable for the dissection of myology
than the last. The muscular texture is in old subjects nearly as in
these last, flaccid and loose; we feel this flaccidity under the skin
in the solæus, the gemelli, the biceps, &c.; it does not prevent each
fibre from being dense and tough. In general the muscular cohesion is
in the inverse ratio of the age; the muscles of a young man are firm
and compact; they are not moveable under the skin. Towards the fortieth
year and afterwards, we begin to perceive more laxity; the calves of
the legs vacillate in great motions; the glutei and in general all
the prominent limbs exhibit also this vacillation, especially if the
individual is thin. The muscles become more and more susceptible of
moving thus, as we approach old age, a period in which the least motion
makes the whole muscular system vacillate. Why? Because the muscle is
no longer in sufficient contraction; it is as it were too long for the
space it fills. This appears to be owing to the circumstance that the
contractility of texture has diminished in the last age; we can be
convinced of this by cutting transversely for comparison a muscle in
an old man and a young one; it retracts more in fact in an opposite
direction in the second than in the first. This contractility of
texture approximates all the particles of the muscle when at rest; it
can no longer produce this approximation; the muscle remains loose.
Authors have not sufficiently observed this remarkable phenomenon which
the muscular system experiences from the progress of age, a phenomenon
which is really the index of its degree of contractile power.

Frequently in old age the muscular texture loses its colour and takes a
yellowish one and has a fatty appearance, though however this colour
does not arise from the fat, but from the absence of the colouring
substance of the blood. I have often made this remark. If we strip all
the surrounding fat from these pretended fatty muscles, and leave them
only their texture, combustion or ebullition extracts no animal oil
from them; they are in their fibrous state as usual; the colour only is
different. I have remarked that the deep muscles of the back and those
placed in the vertebral depressions are much more subject than all the
others to lose their colour and to exhibit this yellowish aspect, an
aspect that is rarely ever seen in the whole system, but only in some
insulated muscles. Adults are subject, though less frequently however,
than old people, to this alteration. Many times we see limbs that are
poorly nourished, with an aspect, nearly the same. In recent palsies,
in those even of three, four or six months, there is in general no
change in the limbs; the muscles preserve their colour and their size;
but at the end of a longer time, the absence of motion, perhaps also
the deficiency of nervous influx, terminate by altering the nutrition
left for a long time untouched without this influx, and then the
muscles change colour, contract and diminish. But this phenomenon is
not always constant, and there are at the Hôtel-Dieu hemiplegias of
six, seven and even ten years, without the limb of the sound side
predominating in its nutrition over that of the diseased one.

External pressures for a long time continued upon a muscle, produce
nearly the same effect as want of nourishment; they discolour and
whiten it by preventing the circulation in it. Those who make use of
straps constantly passed under the arms, who habitually have girdles
round the abdomen and who lift burdens, have often the muscles
corresponding to the constant pressure they experience, in the state
of those of old people. I would remark that these muscles contract
notwithstanding; which proves that the colouring substance is not of
absolute necessity to muscular action.

The blood is carried in general in much less quantity in the muscles of
old people; their vessels are in part obstructed; this is what disposes
them to the state of which I have just spoken.


V. _State of the Muscular System at Death._

At the instant of death, the muscles remain in two different states;
sometimes they are stiff and inflexible; sometimes they allow the limbs
to execute motions very easily. It is sometimes necessary to make an
effort to bend the thigh of a dead body; at others the least touch is
sufficient to do it, as for example in asphyxia, from charcoal. These
state of rigidity and relaxation have infinite degrees. The first is
sometimes so great, that the subject raised against a wall remains
standing; at other times it is nothing. Some muscles are stiff in
subjects, while others are relaxed. It appears that these different
states depend upon the kind of death, upon the phenomena that accompany
the last moments. But how do they precisely happen? It is an object
of interesting research. I have remarked that the muscles remaining
stiff at the instant of death, are often torn with ease, if we attempt
to force the motions of the limbs to which they go; that the tearing
hardly ever takes place on the contrary in those remaining supple,
whatever may be the impulse communicated at their moveable points; it
is necessary to draw them directly, attach weights to them, &c. to
produce this phenomenon, which is then easy.

The muscular texture is never preternaturally developed in the
different organs in which nature has not originally placed it, as
happens in the osseous, cartilaginous and even fibrous textures. If
it were developed, it would not belong to animal but to organic life;
because in order to depend upon the first, the cerebral nerves are
essentially necessary, the muscle being but the agent of the motions
which the latter communicate.


END OF VOL. II.

       *       *       *       *       *

Transcriber's Notes

Obvious typographical errors have been silently corrected. Variations
in spelling and punctuation remains unchanged.

Italics are represented thus _italic_.

The various tables used curved braces to indicate groups.
For clarity these have been replaced by rectangular braces.





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