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Title: An Essay on Contagious Diseases - more particularly on the small-pox, measles, putrid, - malignant, and pestilential fevers
Author: Wintringham, Clifton
Language: English
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                             [Decoration]

                                   AN
                                 ESSAY
                                   ON
                         _Contagious Diseases_.

                             [Decoration]



                                   AN
                                 ESSAY
                                   ON
                         _Contagious Diseases_:


                           More particularly

    On the _Small-Pox_, _Measles_, Putrid, Malignant, and
    Pestilential Fevers.


                       By _Clifton Wintringham_.


                                 YORK:

    Printed by _Charles Bourne_ for _Francis Hildyard_, and are to
    be Sold by _W. Taylor_, at the Sign of the _Ship_ in
    _Pater-noster-Row_ LONDON, 1721.



                              [Decoration]


                                  THE
                                PREFACE.


_The Design of this small Treatise being to deduce the Causes, and
explain the_ Phoenomena _of some of the most Fatal Diseases which
afflict Mankind, can stand in Need of no Excuse, whatever the_
_Performance it self may; and especially at a Time, when not only
several of them Rage amongst us with uncommon Violence, but we are Daily
threatned with the dreadful Calamity of a Raging Pestilence. I have
endeavour'd to reduce these Diseases to the same Simplicity with Others,
to speak Intelligibly of them, and show the real Changes in the Animal
Oeconomy, from the Principles of the Modern Philosophy._

_The Learned Authors who have already wrote on this Subject, have
rejected this Part of it, as being so easie and obvious as to need no
Explanation. I doubt not indeed but this is their Case: But how easie
soever it may be to explain these_ Phoenomena, _'tis not every one,
conversant in the Practice of Physick, that will give himself the
trouble to deduce them; and 'tis for such chiefly that this small Tract
is designed; to_ _whom if it prove any way serviceable, I shall gain the
End I proposed by it._

    York, _June 1st_.
        1721.


                             [Illustration]


                                ERRATA.

       Page 8. Line 20. before Contagion insert _a Pestilential_.
                    Page 52. Line 17. read _Buboes_.



                             [Illustration]


                                   OF
                         _Contagious Diseases_.


                              [Decoration]


                                CHAP. I.

_Contagious Diseases_ are generally defin'd by Physicians to be such, as
are capable of being communicated to us by the Air, or the Effluvia of
Morbid Bodies. When the Cause producing these Diseases is general, and
not occasioned by the peculiar Qualities of particular Places, but
brought from Abroad, they are stiled _Epidemic_.

The Causes therefore of these Diseases must either be generated in the
Air, or produced from the Effluvia of Animal, Vegetable, or Mineral
Substances floating in it. And consequently the Effects of the
Contagious Particles must be extreamly various, according to the
Qualities of the Bodies from which they are produced.

When any of these Causes is of so deleterious a Nature, as not only to
be Infectious, but to destroy all or most of those that are affected by
it, That Disease is called a Pestilence.

But before I proceed to examine the particular Properties and Effects of
the Contagious Particles, it will be Necessary to Demonstrate the
following Propositions.


                                PROP. I.

The Magnitude of the Particles of the Blood being increased,
Obstructions will be formed in the Ramifications of the smaller Vessels,
which will happen sooner or later, in Proportion to the increased
Magnitude of the Particles, and the smallness of the Vessels.


                            _Demonstration._

                             [Illustration]

Let the Canal A be an Artery of a middle Size, sending out the Branches
C, D, E, F, G, H; Let the Dotts represent the increased _Moleculæ_ of
the Blood, it is evident that these must be stopt some where or other in
the Ramifications of the Vessels C, D, E, F, G, H, whenever the
Diameters of the _Moleculæ_ exceed those of the containing Vessels.


                               PROP. II.

The Magnitude of the Particles of the Blood being increased, those
Capillary Vessels nearest the Heart will be soonest obstructed, and
_vice versa_; The rest in Proportion to the Velocity of the Blood,
Diameters of the Canals, and their Distance from the Heart.


                            _Demonstration._

This is sufficiently evident from the foregoing; For the sooner those
_Moleculæ_ arrive at the Capillary Vessels, the sooner those Vessels
will be obstructed, and _vice versa_, and consequently _cæteris paribus_
the Capillaries of the Branches C, H, in the preceeding Figure, which
are nearest the Heart, will be sooner obstructed than those of E, F.


                               PROP. III.

The Magnitude of the Particles of the Blood must be increased either by
the Union of a greater Number of them than in a Natural State; Or by the
Alteration of their Figure, by which their Surfaces become larger than
before.


                            _Demonstration._

This is evident from the Observations of _Lewenhoeck_ and _Malpighius_
on the perspirable and other ultimate Vessels, which are visible by the
Microscope, and consequently larger than the Orifices of the Lacteals,
which the best Glasses will not discover. Whence it will follow, that no
Particle can pass this way into the Blood, which single can obstruct the
Vessels, and consequently this Effect can only be produced by the Action
of the Particles upon each other, _viz._ either by the Union of a
greater Number, or some Alteration in their Figures, whereby their
Surfaces become larger than before. Thus the Globules of the Blood as
appears by the Microscope, are nearly of a Spherical Figure, which being
the most capacious, as well as most apt to constitute a Fluid Body, by
touching in the fewest Points The farther any Particles deviate from
this Figure, the more likely they will be to obstruct the Vessels, and
_vice versa_.


                               PROP. IV.

The Contagious Particles being admitted into the Blood, do there
coagulate its Parts, and form _Moleculæ_ of a larger Size than ordinary.


                            _Demonstration_

The Force of the Heart and Cavities of the Canals being the same, when
the Infection is first taken, as before, the Blood would pass with the
same Facility thro' the Vessels as at other Times, and Obstructions
could not be formed, were not the _Moleculæ_ thus increased; as our
Senses show they are by the Eruption of Pustules in the Small-Pox, by
the great Inflammations, Mortifications, Buboes, and Carbuncles in
Malignant and Pestilential Fevers; and consequently the Contagious
Particles do increase the Bulk of several of the constituent Parts of
the Blood, by altering the Figures of its Particles, and forming
_Moleculæ_ of a larger Size than in a Natural State.



                              [Decoration]


                               CHAP. II.


It has been the constant Observation of Physicians, as well ancient as
modern, and confirm'd by numerous Instances, that a hot and moist
Constitution of the Air, joyn'd with southerly Winds, was generally a
Fore-runner of malignant and Pestilential Fevers. Thus _Hippocrates_
observes, that the Constitution of the Air preceeding that malignant
Fever describ'd in the 3d Book of his Epidemics, 'was calm, moist, and
southerly, and succeeded a hot, and dry Season; the Winter, calm,
cloudy, rainy, warm, southerly; some Showers, and Northerly Winds about
the Equinox; the Spring, calm and southerly, with great Rains; the
Summer very hot, with little Wind, and much Rain about the Dog-days[a].
Some Authors led by the Title of this Book of his Epidemics, _viz._
[Greek: Katastasis Loimôdês], or the Pestilential Constitution, have
imagin'd the Diseases here spoken of, to be the same with that terrible
Plague describ'd by _Thucydides_, which taking its Rise in _Æthiopia_,
and passing thence thro' _Lybia_ and _Ægypt_, miserably harass'd all
_Persia_, _Phoenicia_, _Judea_, _Greece_, and _Coele Syria_, and was one
of the most dreadful Calamities of this kind that ever appeared in the
World. But whosoever will give himself the Trouble to compare the
Symptoms of the Fevers here described by _Hippocrates_, with those
related by that accurate Historian[b], who both had it himself, and
visited many others in it, will find that there is not the least
Similitude between them. The one being highly infectious, and not the
least Appearance of Contagion in the other: _Galen_ also the best
Interpreter of _Hippocrates_, in his Comment on this Book of his
Epidemic's suspects, this Title to be spurious, tho' both he and others
observe much the same Constitution of the Air to be the Fore-runner of
these Diseases.

    [a] _Hippoc._ Epidem. lib. 3. sect. 3. _Galeni_ Com. in hunc
        Loc. _Titi Lucret_, lib. 6.

    [b] _Thucydides_ lib. 2.

[Sidenote: _What Places most
Subject._]

Pestilential and Malignant Fevers, are likewise observ'd to be the most
frequent in those Places where the Climate is hot and scorching, and
especially when Rains fall in such Seasons of the Year. Thus in _Ægypt_
and some other Parts of _Africa_, if Rains fall during the Months of
_July_ and _August_, the Plague usually breaks out the _September_
following[c].

    [c] _Joan. Leon._ Hist. _Afric._ lib. 1. cap. 10. _Purchas_
        Pilgrim. lib. 6. cap. 17.  _Athan._ _Kircheri Scrutin.
        Pestis_, pag. 179.

This is still more remarkable in such Places, as not only are Situated
in the forementioned Climate, but are likewise deprived of a constant
Succession of pure and clear Air. An Instance of this we have in _Grand
Caire_, which besides being subject to the common Disadvantages of the
Country, (as are a Climate hot and scorching, a Situation low and flat,
exposed chiefly to the warm Winds, their Water fetid and stagnating,
being reserv'd in Vaults and Canals, which are Annually fill'd by the
Overflowing of the River, the Air abounding with putrid Steams and
Exhalations, arising from the Parts of Animals, Vegetables, and other
Substances brought down and there deposited by the River), lies close
under the Hill of the Castle, by which all Wind and Air is intercepted,
which causes such a stifling Heat there, as ingenders many Diseases.[d]

    [d] _Therenot_'s Travels, Part. 1. pag. 128.

That these may justly be esteem'd the Causes of the greater Frequency of
these Diseases in this Place, than others in the same Climate, appears
from their being so rarely known in those Places, which tho' equally
hot, enjoy an Air free from Vapours.[e] Thus in _Numidia_ and some other
Parts of _Africa_, the Plague is scarce to be found once in a hundred
Years, and hardly at all in the Land of _Negroe_.[f]

    [e] _Piso_ Hist. _Ind._ & _Brasil_.

    [f] _Purchas_ Pilgrim. lib. 6. cap. 13.

[Sidenote: _Several Causes of the
Plague._]

The other Observations of the Causes of these Fevers, may be reduced to
such as arise from the Stinks of stagnating Waters in hot and close
Weather, to some putrid Exhalations of the Earth, to the Parts of
Animals and Vegetables putrifying in the open Air, or the taking of
corrupt & unwholsome Nourishment.

Of the first kind was that at _Selinis_, occasioned by the stinking
Exhalations of the stagnating Waters adjacent, which the discerning
_Empedocles_ removed by scouring its Ditches from their Filth, by a
fresh Current of Water drawn from two Rivers in the neighbouring
Country[g].

    [g] _Plutarchi_ Lib. [Greek: peri polypragmosynês].

To the second Class may be reduced that Pestilential Fever, which the
same great Philosopher check'd at _Agrigentum_, by stopping the Mouths
of some neighbouring Mountains, whose pernicious Fumes had infected the
adjacent Country[h]; As also that mentioned by _Ammianus_
_Marcellinus_, which broke out in _Seleucia_, and over-ran a great Part
of _Greece_, _Italy_, and _Parthia_, and took its Rise from the opening
of an old Vault in the Temple of _Apollo_.

    [h] _Diog. Laert._ in Vit. Emped.

To the Third belong, such as are occasioned by the Parts of Vegetables
and Animals, especially those of Men, putrifying in the open Air. As was
that mention'd by _Livy_, which over-ran a great Part of _Italy_, and
owed its Rise to the dead Bodies of the _Romans_ and _Fidenates_ left
unburied in the Field of Battle[i]. Analogous to this was that which
from the same Cause appeared in _Germany_, _Anno 1630_; And likewise
that mentioned by _Ambrose Parree_ from the same Cause; as also that
mentioned by _Diodorus Siculus_, occasioned by great Quantities of
Locusts driven by Winds into the Sea, and thence cast up in Heaps on the
Shore. To this likewise must be reduced those Malignant and Pestilential
Fevers, which so frequently attend Camps and Seiges, especially in the
hot Eastern Countries, whose numerous Armies frequently feel the dismal
Effects of these stinking Fumes: As do likewise the vast Caravans of the
_Mahometans_ in their Annual Pilgrimages to _Mecca_.

    [i] _Tit. Livii_ Hist. _Roman._

To the last belong those Pestilential Fevers, which take their Rise from
a preceeding Famine, as was that in _Judea_ in the time of _Herod_[k],
in which the Product of the Ground being consumed by the great Heat, and
long Drought of the preceeding Summer, the poorest sort of People were
obliged, thro' the Scarcity of Provisions, to make use of such Food as
afforded unwholesome and putrifying Juices.

    [k] _Joseph_. Antiq. _Judæor_. lib. 15. cap. 12.



                              [Decoration]


                               CHAP. III.


The Changes wrought in the Animal Oeconomy from the above-mention'd
Causes, may be reduced to such as depend either on the Increased Heat of
the Air join'd with its Humidity; Or to such as are produced from the
particular Qualities of the putrid and Contagious Particles floating in
it; Or to the united and complicated Effects of all together.

[Sidenote: _Effects of a hot and
moist Air._]

The Alterations produced in the Body from a greater Heat continually
surrounding it, provided it be not Excessive, are a Rarefaction of the
Juices, and Relaxation of the _Fibres_ on the Surface of the Body, and
greater Derivation of the Fluids that way. Whence proceeds a large
Evacuation of the perspirable Matter. This being continued in a greater
Proportion than in a Natural State, will gradually deprive the Blood of
its Aqueous and Spirituous Parts, and leave the remaining serous Part
more stock'd with acrid and pungent Salts, and the Gross, Terrestrious,
Oleaginous, and Viscous Particles more firmly united by their nearer
Approach, and stronger Cohesion to each other. This greater Heat or
Quantity of Fiery Particles, continually surrounding the Body, will
necessarily insinuate it self into, and unite with the Saline,
Sulphureous, and other Particles, in the same manner as we see it does
with other Substances, both Solid and Liquid[l]; And likewise by
increasing the Velocity of the Circulation and Attrition of the
Particles against each other, render them on these Accounts also more
Volatile, Pungent and Stimulating, and consequently the Blood will
consist of Particles more gross and inspissated or coagulated, and
likewise of those of a more acrid and pungent Disposition than in a
natural State.

    [l] _Boyl_'s Experm. Nov. de Pond, Ignis & Flam. _Newtoni_
        Optic. Quæst. 21 & 22.

The Blood being in this depraved Condition, the rest of the Animal
Juices must degenerate in Proportion thereto, and the Nervous Fluid, as
it consists of the most volatil and subtil Parts, be extreamly acrid and
pungent, as well as unequal in its Texture and Fluidity, from the more
viscous Parts contain'd in it.

[Sidenote: _Putrid Fevers how
produced._]

This then being the State of the Blood and other juices of the Body, it
is easy to perceive how from very Slight, and otherwise trivial
Occasions, a Fever of a very Malignant Nature may be produced. Thus the
perspirable Matter from a slight Cold taken being retained, or the
Vessels any otherwise filled by Irregularities in Diet, or others of the
Non-naturals, the Weight of the moving Fluid will be increased, and the
Circulation be more languid and slow. Whence the intestine Motion of the
Particles of the Blood being diminished, the viscous Parts will cohere
more strongly and in greater Quantities than before, and obstruct the
Capillary Arteries, especially in the Extremities, and a Coldness,
Stretching, Yawning, Torpor, _&c._ necessarily succeed, the constant
Attendants of a beginning Fever; All which will bear a Proportion to the
Quantity retain'd, and the Viscosity of the moving Fluid.

These Disorders will necessarily be increased on account of the Air's
Spring being weakned by its Heat, the Vessels of the Lungs being less
inflated, and the Globules of the Blood less broken and divided, and the
more especially in a humid Air, Heat and Moisture necessarily relaxing
the Tone of the Fibres and Vessels, and rendring them less Springy and
Elastic. Hence then the Quantity of Spirits being diminish'd, and their
Motion more slow, the Contraction of the Heart and other Muscles will be
more weak and languid, and being stimulated by the Acrimony of the
Circulating Liquors, must contract more frequently than in a Natural
State; The Consequence of which is Weakness, Faintness, Thirst, and
Dejection of Spirits.

These and the preceeding Symptoms will necessarily continue, 'til such
time as the gross and viscous Matter, being shook and loosen'd by the
Action of the Capillary Vessels, is washed away into the Veins by the
force of the Circulating Fluids, and there continues its Course with the
rest, 'til it be either attenuated and secreted, or lodged again in the
Capillaries to excite new Disorders.

[Sidenote: _Malignant Fevers._]

Now if to this evil Disposition of the Air be added a number of pungent
stimulating Particles, whether bred in the Body or floating in the Air,
and thereby communicated to the Blood, which are apt to coagulate the
Animal Juices, so as to form _Moleculæ_ of such Shapes and Sizes as more
firmly obstruct the Capillary Vessels, and at the same time stimulate
and corrode the nervous Parts; It will necessarily happen, that the
preceeding Symptoms must be highly exasperated, and a Fever of a much
worse Nature produc'd.

Hence then must follow a violent Hurry and Colluctation of the Fluids,
the Viscid and coagulated Parts of the Blood in some Parts obstructing
the Circulation of the Juices, and the Acrid, Volatil, and Fiery Parts,
rarefying and dissolving others of the more Liquid, to the greatest
degree of Pungency and Volatility imaginable.

Hence it is easy to perceive how the Motion of the Blood must
necessarily be in some Parts more languid, by the Cohesion of the more
Viscous parts, in others quicker, join'd with a pungent and stimulating
heat, from the increased Velocity and Acrimony of the moving Fluid, and
the various Actions of the Particles upon each other, and their Impulses
on the containing Vessels; As also how these are capable of almost
infinite Variations, in Proportion to the different Quantities and
Qualities of the constituent Particles. Hence then appears the Reason of
that wandering and uncertain Heat and Coldness, in different Parts of
the Body at the same time. Hence appears the Reason of that great
Inquietude and Anxiety, of those uncertain and partial Sweats,
Watchings, Tremors, stretching Pains of the head, and the like, as will
be more fully shown hereafter.

But before I proceed to explain the Nature of a Fever truly
Pestilential, it will be necessary to observe, that notwithstanding the
foremention'd putrid Disposition be generally a Prelude to a
Pestilential Constitution of the Air, yet it has never that I know of
been observ'd, that these Causes alone at their first Onset, produced a
real Plague or Pestilential Contagion, without the Concurrence of some
preceeding Infection, either brought from abroad, or gradually augmented
from the increased Putrifaction of the Air, and Poisonous Steams of
Morbid Bodies.

Thus the putrid Air of Camps in hot Countries is frequently found to
produce Pestilential Fevers, but this never happens at their first
Onset; The Diseases first appearing being Fluxes, Putrid, and afterwards
Malignant Fevers; which being exasperated and propagated by the Virulent
Effluvia of Diseased Bodies, and the increased Putrifaction of the Air,
grow up gradually to those of a Pestilential, and exceedingly infectious
Disposition.

[Sidenote: _Of Putrifaction &
Fermentation._]

Now Putrifaction being only a kind of Fermentation, wherein the
Particles of a putrifying Body are put into an intestine Motion, and by
their Action and Attrition broken and divided, and since all fermenting
Substances do emit vast Quantities of small separable Parts, it will
necessarily follow, that the most subtil and active Particles of the
Purifying Body will be elevated into the Air, and float in it.

[Sidenote: _Effluvia from putrified
Bodies what._]

These Effluvia consist of the finest and most volatil saline and
oleaginous Particles, highly attenuated and set at Liberty from the
gross Oil and Terrestrious Part, as appears from the Distillation of
such Substances, all which afford great Quantities of a pungent and
volatil Salt. It is likewise observable, that the subtil Oleaginous
Particles being specifically lighter, as well as more easily attenuated
and divided than those of a Saline Nature, will be thrown off in greater
Proportion in the beginning of the Fermentation or Putrifaction than the
heavier Salts will be, which must either be more attenuated and
volatilised, or require a greater force to raise them into, and sustain
them in the Air than the former, and consequently the greatest Emission
of these saline Particles will be after the Fermentation has been for
some time continued; As we find it happens in all fermenting Liquors, as
Wine, Beer, Cyder, and the like. All which emit, during the
Fermentation, greater Quantities of Particles of an active attenuated
Oil or Spirit for some time, than of a Saline Nature, which requiring a
longer time in order to attenuate them, are not raised till the former
are in a manner quite exhaled, as appears from collecting the Steams of
fermenting Liquors, and of those which are turn'd sower by Distillation,
and consequently the Exhalations arising from putrifying Bodies will
after some time consist mostly of Saline Particles highly attenuated and
volatilised, and those not wrapt up and sheathed in the Oily ones, and
thereby render'd innocuous, and often useful to the Body, but naked and
exceedingly acrid and poignant.

How unfit an Air stock'd with these kind of Particles is for
Respiration, appears from several of Mr. _Boyl_'s Experiments on
Animals, shut up with putrified Air in the Receiver, most of which with
incredible Inquietude die sooner than in _Vacuo_, as also from the
pernicious Effects of the Steams of Vaults, Mines, the _Grotto de Cane_,
and such like. But besides this Inaptitude of such Air to expand the
Pulmonary Vessels, these minute and pungent Particles may be considered
as so many _Stimuli_ or Lancets, acting upon and penetrating the Coats
of the Stomach, Lungs, and other Vessels. On which Account they are not
only capable of creating great Disordes, as Inflamation, Pain, Sickness,
Anxiety, Vomiting, _&c._ in the Stomach and Nervous Parts; But likewise
being carried immediately into the Blood, will there stimulate the
ultimate Vessels, ferment, dissolve, or coagulate the circulating Juices
according to the particular Qualities and Quantity of the Contagious
Particles. Nor is it unlikely, that from the various Action of the
Particles upon each other, and their different Combinations in a
stagnating Air, Particles may be formed of Qualities vastly differing
from, and in their Force almost infinitely exceeding those of their
Primogenial Salts and first Principles, as in Sublimate, some
Preparations of Antimony, _&c._ Instances of which those versed in
Chymistry are no Strangers to.

[Sidenote: _Infectious Particles how
produced._]

Now supposing the Blood Saturated with these kind of Particles, and a
Malignant Fever produced by their means, we all know that the Blood in
this State throws off vast Quantities of subtil and active Particles
thro' the Perspirable, Salival, and other Excretory Ducts of the Body,
which not only must load the adjoining Air with great Quantities of
them, and render it capable of producing more dismal Effects than the
preceeding, but also the Particles thus thrown off must be endued with a
more acrid and pungent Disposition than the former, inasmuch as they are
more subtily divided and attenuated by the Force of the Fever, than
those in the preceeding Disposition of the Air, where so powerful an
Agent was wanting, And consequently produce a Fever of a most infectious
and deleterious Nature; And especially when the Infection is taken
toward the latter end of the Disease, at which time the Saline Particles
will be more exalted and volatilised, as well as thrown off in greater
Quantities, and thereby made more capable of producing an infectious
Contagion.

For the Blood in these Circumstances may not unaptly be compared, as was
before hinted, to a fermenting Liquor, whose Parts being constantly in
Motion, are continually throwing off great Quantities of subtil and
active Spirits, capable of exciting the same Fermentation, and producing
the same Qualities in those of the like Species, as appears from our
manner of fermenting Ale, Beer, _&c._ with Yeast, which is a Spirituous
Ferment, and also from the Sower Ferments used in making Vinegar, _&c._

Analogous to this we may observe, that the Blood in different Diseases,
as well as different Animals, throws off great Quantities of active
Particles, which when mixed with the Blood of a Healthful Person, are
capable of exciting the same Fermentation and Disorder in the Animal
Juices, with those of the Morbid Animal from which they exhale, as we
find in the _Small-Pox_, _Measles_, _Saliva_ of a _Mad-dog_, and the
like.

This then being the Disposition of the Blood and other Juices, in those
Fevers which we call Pestilential, it is evident, that whatever the
particular Substance of the Contagious Particles may be, they must be
endued with such Qualities as will Coagulate the Animal Juices,
Stimulate the _Fibres_ to frequent Vibrations, cause Obstructions in the
Capillary Vessels, and render the Blood and other Juices of the Body
exceedingly Acrid and Pungent, as appears from hence and the foregoing
Propositions; The Symptoms and Consequences (_cæteris paribus_) being
the same, whether the Disease has gradually grown up to this Height, or
took its Rise only from Contagious Particles brought from abroad.

[Sidenote: _How propagated._]

This is the Method by which I suppose these Contagious and Pestilential
Particles to be first generated and produced, in those places which are
most subject to them, and thence propagated first into the
Neighbourhood, and afterwards to greater Distances by way of Intercourse
and Commerce. The Pestilential _Effluvia_ being pack'd up and conveyed
in Goods of a soft and loose Texture, as Silk, Wool, Cotton, and the
like; And so much the more easily, as the Air into which these infested
Materials are brought, is predisposed to act in full Concert with them;
as happens in all Places at some times more than others; At which time
if these infectious Particles be communicated, they exert their Rage
with the utmost Violence, but frequently are either dissipated and lost,
or produce Diseases of less fatal Consequence, in an opposite
Disposition of the Air.

[Sidenote: _Why the Plague ceases._]

Thus hard Frost, strong cold and Northerly Winds, are found frequently
to put an End to, or at least bridle the Fury of Contagious Diseases,
and render them more mild and curable, as was observable in the
Beginning of the last great Plague in _London_[m], and frequently taken
Notice of in other places by the Writers on this Subject. Consonant to
this we find in _Ægypt_, that the Rising of the _Nile_ by giving a fresh
Motion to, and altering the Disposition of their stagnating and putrid
Air, by the mild Vapours and Nitrous Exhalations[n] issuing from it,
immediately checks the Raging of the Plague, and reduces it to a Fever
of a more mild and curable Nature; insomuch that as _Purchas_ and others
inform us, if there die in _Grand Caire_ 500 Persons of the Plague the
Day before, yet upon the Increase of the River it ceases to be
Pestilential, and none die of it[o]. And indeed it can hardly be
imagin'd, how the Plague when it has once got establish'd in any Place,
shou'd cease but with the Destruction of all or most of the Inhabitants,
was it not checked by some Alteration in the Disposition of the Air, and
gradually reduced to a Fever of a more mild and curable Disposition.

    [m] _Hodges_ de Peste.

    [n] _Boyle_'s determ. Nat. Effluv. cap. 4. _Plot_'s Nar. Hist.
        of _Staffordsh._ cap. 2. pag. 42.

    [o] _Purchas_ Pilgrim, lib. 6, cap. 7. _Sandy_'s Travels, lib.
        2. cap. 97.

It will I think be needless to show, that the Distempers here treated on
are propagated by Contagion; But it may not be altogether unnecessary to
explain by what Methods these Alterations in the Animal Oeconomy are
brought about, and especially as the Means by which they are chiefly
communicated, have not that I know of been fully examin'd.



                              [Decoration]


                               CHAP. IV.


[Sidenote: _Of a Pestilence by
Contagion._]

The Contagious Particles whether they be generated in the Air, or
produced by the _Effluvia_ of Morbid Bodies, being sustain'd in it, are
thereby applied to the Surface of our Bodies, with a Force equal to the
Pressure of the Incumbent Atmosphere. This Pressure upon the External
Superficies of a human Body of a middle Size, has been demonstrated to
be equal to 39900 Pounds Troy-weight, and consequently supposing the
Body in every Part encompassed with these Particles, the whole Force
with which all these Particles are on this Account propell'd into the
Body, will amount to the aforesaid Sum. But every single Particle is
only applied with the Force of a Column of Air of the Height of the
Atmosphere, and whose Base is equal to the Surface of that Side of the
intruding Particle, opposite to the cutting Angle. Now the Contagious
Particles from their extream Smallness and pungent Angles, may not only
be consider'd as Bodies applied to us with the preceeding Force, but
likewise as so many small Knives or Lancets, acting upon and penetrating
the Coats of the Lungs and Surface of our Bodies, with a Force
proportional to the Smallness of their cutting Angles. This appears not
only from several Propositions in Mechanics, but even to our Senses, by
the strong Contraction of a Cord or Fiddle-string in moist Weather. The
Particles of Water from their exceeding Smallness, being protruded into
the Cord, with a Force capable of Raising the greatest Weights. Now if
to these be likewise added the strong attractive force of these small
Volatil Particles, occasioned from their Exiguity, it will be no
difficult matter to conceive, that they are capable of penetrating the
Vessels of our Bodies. Thus the Attractive Force of the Magnet is
greater in Proportion to its Bulk, in Small ones, than in those of a
larger Size, from the greater Proximity of all its Particles to each
other. And 'tis on this Account that Sir _Isaac Newton_ computes the
Attractive Force of the Particles of Light, to be to that of other
Bodies, as 1000000000000000 to 1, in Proportion to the Quantity of
Matter contained in them[p].

    [p] Optic, in sine Quest. 22.

This I think is sufficient to shew, that these Acrid and Pungent
Particles are able to penetrate the Surface of our Bodies, and get into
the Blood that way; And indeed Experience it self confirms it in all
other Pungent and Acrid Substances, as _Garlic_, _Cantharides_,
_Arsenic_, and all _Pungent_ and _Corroding_ Bodies.

[Sidenote: _The Pressure of the Air
on the Internal Surface of the Lungs
in Breathing determined._]

But tho' the whole Superficies of our Bodies are Penetrable by these
Poisonous Particles, yet the principal Mischief is communicated to the
Blood in its Passage thro' the Lungs. For considering the prodigious
Number of the Pulmonary Vesicles, into all which the Air enters in
Respiration, and likewise the vast Increase of their Surfaces on that
Account, and also the greater Force by which these Particles are applied
to the Internal Surfaces of the Vesicles in Expiration, in Proportion to
that whereby they are applied to other Parts of the Body of equal
Superficies; it will evidently appear, that the Contagion is chiefly
communicated by these Vessels to the Blood. For it appears by the
Barometer, that every Inch Square upon the Surface of our Bodies is
pressed upon by a Weight nearly equal to 1800 Drams, when the Mercury
stands highest in the Barometer. Now supposing with Dr. _Kiel_[q] that
both the Lobes of our Lungs contain 226 solid Inches, of which only 1/3
or 75 Inches are Vesicles. Supposing also the Diameter of a Vesicle to
be 1/50 Part of an Inch, the Surface of the Vesicle will be .001256 and
the Solidity .0000043, by which if we divide 75 the Space fill'd by the
Vesicles, the Quotient, _viz._ 17441860 X .001256 the Surface of a
Vesicle, gives the Sum of the Surfaces of all the Vesicles, = 21906.976
square Inches. Which Sum being multiplied by 1800, the Number of Drams
which every square Inch of the Surface of our Bodies sustains, gives the
Weight which the whole Internal Surface of the Lungs sustains by the
sole Pressure of the Atmosphere, when the Mercury stands highest in the
Barometer, equal to 39442556.800 Drams, equal to 410859.966 + 64/96 lib.
_Troy_ weight, as appears from the known Laws of _Hydrostaticks_[r].

    [q] Animal Secret.

    [r] _Marriote_'s Hydrostaticks.

Now if to this be added the increased Pressure of the Air, against the
internal Surfaces of the Vesicles in Expiration, the Force will be found
to be still greater. For supposing the Diameter of the _Larynx_ to be
equal to O.5 of an Inch; Supposing also the Pressure of the _Larynx_ in
an ordinary Expiration, by which the Force of the expired Air exceeds
the Pressure of the Atmosphere, to be two Ounces, as has been found by
Experiment[s], the Pressure of the Air in an ordinary Expiration upon
the Internal Surface of the Vesicles of the Lungs, will on this Account
only be equal to 1844736 Drams, or 19216 lib. _Troy_ weight, which added
to the Pressure on the Vesicles by the Weight of the Atmosphere, amounts
to 39444401.536 Drams, or 410879.182 + 64/96 Pounds _Troy_ weight. But
the Pressure of the Air on all the rest of the Surface of our Bodies
amounts but to 39900 lib. _Troy_, which is to the Pressure upon the
Internal Surface of the Lungs, as 1 to 10.297 + 28882/39900, and
consequently many more of the Contagious Particles will be communicated
this way, than thro' the whole Surface of the rest of the Body. The
Weights aforemention'd are indeed prodigious, but that is caused by the
great Increase of Surface by the Number of the Vesicles: For it is still
to be consider'd, that the Pressure upon each square Inch of the Surface
of these Vesicles, amounts to no more than the Pressure on every Inch
Square on the Surface of our Bodies, except that Increase which is made
by the Force of Expiration, otherwise these Vesicles cou'd in no wise
withstand so prodigious a Pressure. This Quantity _viz._ 75 Cubic Inches
or thereabouts seems to be emitted from the Lungs in an ordinary
Expiration, for I have found by Experiment, that the Lungs in a large
Expiration will emit above 160 Cubic Inches of Air. Having my self
fill'd an exhausted Receiver of that Size with Air at one Expiration, of
the same Density with that of the Atmosphere.

    [s] _Kiel_'s Animal Secretion, _Edit. ult._

Now if we likewise consider the exceeding Smallness of the Pulmonary
Vessels, and also that the whole Quantity of Blood in the Body must
necessarily pass this Organ, in order to its being attenuated and made
fit for Circulation; It will necessarily follow, that the Alterations
made in the Texture of the Blood by the Poisonous _Effluvia_, are
communicated to it chiefly thro' this Organ. Besides, the Poisonous
Particles do not only Enter into the Blood in greater Quantities in this
Bowel, but when carried by these Passages, are capable of doing much
more Mischief, than if entring in at any other Part of the Body, in
Regard that they are more intimately mixt with it in its Comminution. I
have insisted the more largely on this Argument, because I find that
most who have wrote in this Subject, tho' they do suppose some of the
Contagious Particles may be communicated to the Blood this way, yet lay
the greatest Stress on the Mixture of these Particles with the _Saliva_,
which being swallowed carries them in common with our Nourishment. 'Tis
not Improbable indeed, that many of these Particles may be this way
communicated to the Blood; but it is as Probable, that many of them
which are by this way Communicated, lose much of their Force by their
Mixture with the _Bile_ and other Juices; As we see happens in the
Poison of the _Viper_, which taken at the Mouth is not deadly, but when
mixed immediately with the Blood produces the most violent Symptoms. The
same may be observed from many other Substances, which may be safely
taken into the Body by the common Passages, as most Acids, Spirit of
Wine, and other Substances, but when mixed immediately with the Blood,
by Injections into the Vessels of living Animals, produce Coagulations,
Convulsions, and Death: The principal Reason which has induced
Physicians to suppose, that the Poisonous _Effluvia_ are chiefly
communicated by these Passages, are those violent Vomitings which
frequently accompany it; But this happens equally in many other Fevers,
where there cannot be the least Suspicion of Contagion. The only
Objection to what I have here advanced seems to be, That if the
Contagion was communicated to the Blood chiefly by the Lungs, the
Coagulations wou'd be immediately form'd there, and this Bowel totally
obstructed. But if we consider, that the Chief Application of the Air to
the Pulmonary Vesicles is in Expiration, immediately after which the
Blood enters the _Vena Arteriosa_, whose Branches continually grow
wider, and give Space and Time for the Coagulating Particles to act with
their full Force, this Objection will of it self fall to the Ground.

The Contagious Particles being by these Means got into the Blood, do
there by Coagulating and Inspissating the more gross and tenacious
Parts, and highly Volatilising and Attenuating others of the most
Subtil, reduce the Blood into the above-mentioned State. Thus we see
that _Milk_, which is the Juice of an Animal, by the Addition of a small
Quantity of an Acid Spirit, changes from an equal Texture, to one of a
more gross and viscous, as well as more fluid and watry Substance. The
like may be observed in the White of an Egg and the Blood of an Animal
it self. Analogous to this is that Experiment of _Jo. Bapt. Alprunus_,
who examining the Matter of a Pestilential _Bubo_ by Distillation, found
at first a _Phlegm_, then a more fat and oily Matter, and lastly a Salt
ascending into the Neck of the _Retort_. But what was the most
Remarkable in this Experiment, was the prodigious Stench upon opening
the Vessels, exceeding as he expresses it a Thousand Wounds exposed to
the Summer's Heat, and likewise a Salt so exceedingly Acrid and Pungent,
as to equal, if not exceed _Aq. Regis_ it self[s].

    [s] _Ph. Col._ No. II. p. 17.

I shall not from hence pretend to determine, that an Acid Salt is the
immediate Instrument of these Changes in the Animal Oeconomy, since the
same may be wrought by Spirit of Wine, and other Liquids[t]; and
Experience assures us, that the _Effluvia_, proceeding from the
putrifying Parts of Animal Bodies, abound with a Volatil Alcaline Salt,
as appears by Collecting them by the Bell, or in Distillation, by which
they afford some Phlegm, a most Fetid Oil, and exceedingly Pungent and
Volatil Salt; But this is sufficiently Evident from what has been said,
that whatever the determinate Nature of the particular Particles may be,
they do not only Coagulate the Animal Juices, and increase the Bulk of
the Particles of the Blood, but render the remaining Part exceedingly
Acrid and Pungent.

    [t] _Boyl_'s Hist. Humani Sang. _Friend_'s Emonalogia in Fine.

Consonant to this Dr. _Hodges_ has observed a great Affinity between a
Pestilential and Scorbutic Habit of Body, and that those whose Blood
naturally abounded with Saline Particles, and had the rest Coagulated or
Inspissated, as happens in Scorbutic Constitutions, were more grievously
affected by the Pestilence; and also that most of those who Recover'd of
the late Plague, were very much subject to Scorbutic Diseases: The like
I have frequently observed, where the Small-Pox, Measles, _&c._ seizes
those of a Scorbutic Habit.

Nor is the Blood alone affected by its Mixture with these Saline
_Spiculæ_, but the rest of the Animal Juices also in Proportion, and
especially the Nervous Fluid, which consisting of the most fine Volatil
and Subtil Parts, will be render'd extreamly Acrid and Pungent: Whence
Pain, Sickness, Inflammations, _&c._ must necessarily succeed.



                              [Decoration]


                                CHAP. V.


The Symptoms accompanying a Pestilential Fever are Yawning, Stretching,
Coldness, frequently to the greatest Extremity, Shuddering, suddain
Pains in the Head, Giddiness, Loathing, Vomiting, a low unequal Pulse,
Trembling, great inward Heat, especially about the _Præcordia_, Coldness
of the Extremities, uncertain Sweats, Inquietude, Stupor, Delirium,
Watching, Convulsions, Carbuncles, Buboes, Livid Vesications, Purple
Spots, _Hæmorrhages_, which three last are the certain Forerunners of
Death.

But here it is to be observed, that all the preceeding Symptoms do not
constantly happen to every individual Person who is affected with a
Pestilential Fever, but differ both in Number and Degree according to
the Degree of Infection, Virulence of the Contagious Particles, and
Constitutions of particular Persons; Thus the more the Blood is stock'd
with Acrid and Pungent Salts, and other Parts render'd Glutinous,
Coagulated, or Inspissated, the hotter the Season of the Year, the more
violent the Symptoms will be, where the Degree of Infection is equal,
and _vice versa_.

[Sidenote: _Yawning, Stretching
Lassitude._]

These are the first Signs of the Seisure of the fatal Enemy, and take
their Rise from the Slowness of the Motion of the Circulating Fluids.
For the Viscosity of the moving Fluids being increased, and the
_Liquidum Nervorum_ degenerating in Proportion thereto, the Weight to be
moved will bear a greater Proportion to the moving Force than in a
Natural State, and consequently the Animal must be affected with
Weariness, as we find it is in all Cases where the Spirits are exhausted
and weakned, in Proportion to the Circulating Juices. The other two are
the necessary Consequence of this, for the Viscosity of the Fluids
rendring them unfit to pass the small Capillary Vessels, the Pressure on
the _Fibres_ and Vessels will be increased, excite an uneasy Sensation,
and stimulate them to more frequent Vibrations, in order to dislodge the
Enemy: Whence follows a Contraction of the Muscles, and especially those
which serve for Voluntary Motion, and into which the Spirits are most
frequently determin'd: Hence then appears the Necessity of such a Method
and Medicines as may dilute and dissolve the Cohering Fluids, and
especially of such as are taken actually hot, and with large Quantities
of Diluters, the great Activity of the Fiery Particles contain'd in
them, rendring them much more capable of penetrating into the smallest
Recesses of the Body, and disjoining the Coagulated Fluids.

[Sidenote: _Coldness, Shuddering._]

These likewise depend on the too great Cohesion of the sanguineous
Particles, on which account the Circulatory as well as the Motion of the
intestine Particles of the Blood being diminish'd, and many of the
Igneous Particles intangled in the viscous Cohesions, a Sensation of
Cold must necessarily ensue, and especially in those Parts where the
Motion of the Blood is most slow, and its Cohesion increased as happens
in the Extremities. The nervous Juice being likewise for the same reason
determin'd Irregularly, and in less Quantity into the Muscles, sometimes
one, sometimes another of them will be weakly contracted, or a
Shuddering will ensue.

[Sidenote: _A Low, quick, unequal
Pulse._]

These arise from the Secretion of a smaller Quantity of Animal Spirits,
and those too unfit to actuate the Heart and other Muscles, whence their
Contractions will be more weak, and being stimulated by the Acrimony of
the Juices more frequent than in a Natural State. The Derivation
likewise of the Nervous Fluid into the _Fibres_ of the Heart being
irregular, for the Reasons afore-given, the Motion of the Heart, and
consequently of the Pulse, must be weak, quick, and unequal.

[Sidenote: _Loathing, Vomiting._]

These are occasion'd partly by the Contagious Particles being drawn in
with the Breath, and in their Passage tainting the _Saliva_, which when
swallowed Irritates the Nervous Filaments of the Stomach, and partly by
the Secretion of a more Pungent and Acrid Matter by its Glandulous Coat;
as appears from their spontaneous Ceasing as soon as a Sweat can be
procured, and the Discharge of these Acrid Particles promoted by the
Perspirable Glands[u], and seldom otherwise.

    [u] _Sydenham_ de Peste.

[Sidenote: _Diarrhoea._]

A _Diarrhoea_ is likewise oftentimes a Concomitant of these Fevers, and
ever of most dangerous Consequence in the Beginning of the Disease,
inasmuch as it exhausts the Strength of the Patient, and prevents the
regular Expulsion of the Perspirable Matter, by which Experience assures
us that these Contagious Particles are most effectually discharg'd.
These then indicate such Medicines as cleanse the _Primæ Viæ_ from the
Contagious Particles, and other Crudities lodged in them, blunt the
Acrimony of the Saline Particles, and promote the Regular Expulsion of
the Perspirable Matter.

[Sidenote: _Coldness of the
Extremities._]

This is occasion'd by the weak Contraction of the Heart, and greater
Viscosity of the Blood in the Extream Parts of the Body, for the
Circulating Fluids being prest on every Side by the containing Vessels,
the more thin and liquid Part will pass into such Vessels as arise
nearest the Heart, and leave the rest more Viscous and unfit for Motion.
The Force of the Heart in the extream Parts being also much diminish'd,
thro' the numerous Ramifications of the Vessels, the Motion of the Blood
will be more slow, the Cohesion of the Particles of the Blood greater,
and the Obstructions in the Capillaries more fixt than in other Parts of
the Body. Now the Heat of the Body depending in a great Measure on the
Attrition of the Particles against each other, this being diminish'd in
the Extream Parts of the Body, the other must be lessen'd in Proportion.

[Sidenote: _Great inward Heat
especially about the Præcordia._]

This is occasion'd by the greater Intestine Motion and Colluctation of
the Particles of the Blood, and the Expansive Particles of Heat being in
greater Proportion in these than other Parts of the Body, from the more
numerous Ramifications and Obstructions of the Vessels, and their
Proximity to the Heart, as appears by _Prop. 2_.

[Sidenote: _Inquietude Watching._]

These arise from the same Cause as the Preceeding, the great inward Heat
being a constant _Stimulus_ to the nervous Parts, and obliging the Sick
to seek continual Change of Place and Posture, in order to abate this
uneasy Sensation. These therefore indicate the use of such Medicines as
specifically correct the Acrid and Stimulating Particles, restrain the
inordinate Effervescence of the Circulating Fluids, and attenuate the
Viscous Cohesions, of which kind are diluting and attenuating Acids,
temperate Cordials and Anodynes, in such Doses and Proportions as are
agreeable to the Age, Strength, and other Circumstances of the Patient.

[Sidenote: _Delirium._]

This arises from the Inordinate Influx of the _Liquidum Nervorum_,
occasioned from its Acrimony, Viscosity, and Quantity, different from
those in a healthful State. Whence the Reflux of the Spirits to the
Brain will be altogether irregular, and the Representations brought by
them Irrational and Inconsistent. As this Symptom may arise as well from
the increased as lessen'd Quantity, and different Texture of the Fluids,
and Springyness of the Solids; so Regard must be had to the particular
State of the Solids and Fluids in every Individual, for the abating of
this Symptom.

[Sidenote: _Stupor._]

This Symptom necessarily supposes the Flux of the Spirits thro' the
Brain and Nerves in some Measure intercepted or diminished, and
consequently as the preceeding may arise from different and even
contrary Causes, but generally in these Cases shews a greater Degree of
Coagulation in the Juices than the former, and consequently of greater
Danger from the more numerous Obstructions in the Capillary and Nervous
Vessels. Agreeable to which is that Observation of Dr. _Hodges_, That
they who were attended with this Symptom rarely recover'd.

[Sidenote: _Trembling, Faultering in
the Speech._]

These depend on the same Cause as the former, _viz._ On the Diminution
or Obstruction of the _Liquidum Nervorum_, whereby the Muscles are
involuntarily and weakly contracted. As these suppose a more torpid
Motion and greater Viscosity of the Fluids, and less Degree of
Elasticity in the solid Parts, so the Method taken herein ought to be
more active and stimulating than in any of the foregoing Symptoms.
Whence Epispasticks, and the most Volatil Attenuating Medicines are more
necessarily required, and ought to be oftner repeated, than in
preceeding Symptoms.

[Sidenote: _Pain in the Head._]

This is Occasioned by the Obstruction of some of the Capillary Vessels
of the Brain by the Coagulated Part of the Blood, and the wounding of
the Nervous Filaments by the Poisonous Saline _Spiculæ_. Whence the
Blood being resisted in its Motion, must press more strongly against the
Sides of the Vessels, and distend them beyond their Natural Diameters,
and produce a shooting and throbbing Pain; and if the Obstruction
continue or increase, a Phrensy, Inflammation, Suppuration, and Gangreen
of the Part affected. Why this Symptom should be one of the first, as
well as a constant Attendant thro' the whole Course of the Disease,
appears from _Prop. 2_.

[Sidenote: _Carbuncles, Buboes_, &c.]

Hence likewise appears the Reason of Carbuncles, Boboes, Vesications,
and the like, which take their Rise from the same Cause, and are
different only in Proportion to the Viscosity or Acrimony of the
obstructing Matter, and the Situation and Structure of the Part
affected.

[Sidenote: _Purple spots, Hemorrhages_]

These show the greatest Corrosion and Acrimony imaginable in the
Circulating Fluids, so as to be able to break and destroy the very
Vessels themselves, and consequently certain Signs of a speedy
Dissolution of the whole Animal Oeconomy.

[Sidenote: _Dissections of such as
have died of Malignant and
Pestilential diseases._]

The Dissections of such as have died of these Diseases are a farther
Confirmation of the foregoing Theory, inasmuch as they demonstrate a
greater Acrimony and Coagulation in the Juices than other Diseases, by
the numerous Obstructions Inflammations, and Mortifications of different
Parts of the Body. Thus the Stomach and Intestines are commonly highly
Inflamed, and frequently Gangreen'd. The Lungs, Diaphragm, and several
of the _Viscera_ inflamed, obstructed, and beset with Carbuncles and
Purple Spots. The Arteries of the _Dura_ and _Pia Mater_ obstructed, and
stuff'd with Grumous Blood, and often mortified. The Arteries of the
whole Body in general fuller than ordinary, the Veins more empty. The
Vessels about _Præcordia_ much obstructed, highly inflamed, and often
Gangreen'd. The membranous Parts of the Body in general more dry and
rigid than in most other Diseases.



                              [Decoration]


                               CHAP. VI.

                          _Of the_ SMALL-POX.


From what has been said of the Nature of Malignant and Pestilential
Diseases it will follow, that the Contagious Matter producing the
Small-Pox does likewise Coagulate the Blood, and increase the Bulk of
its constituent Particles, and that in such a Proportion as are capable
of obstructing only the ultimate and perspirable Vessels, as appears, in
that it principally, if not solely affects the membranous Parts of the
Body, as well External as Internal. Now these Parts being formed of such
Vessels, the Pustules could not happen in these more than other Parts of
the Body, were not their Vessels thus obstructed, and obstructed they
cou'd not be, but from the increased Bulk of the Sanguineous Particles,
and that in such a Proportion as renders them capable of penetrating
into, but not passing thro' the Cavities of the ultimate Vessels, as
appears from the preceeding Propositions, and consequently, the
contagious Matter producing the Small-Pox, must be indued with this
peculiar Property. And indeed if we allow the different Degrees of
Coagulation in these Contagious Diseases, and which appear even to our
Senses, it will appear, that the Principal if not the sole Difference
proceeds only from the greater or less Bulk and Number of the Coagulated
_Moleculæ_, and Acrimony of the Coagulating Matter. Thus we see that in
Pestilential Diseases, where the Degree of Coagulation and Acrimony of
the Juices are superior to the rest, the Obstructions happen in the
larger Glands, as are those of the Armpits, Groin, _&c._ The Circulation
of the Blood being obstructed, or at lest much retarded in the Capillary
Blood Vessels, as appears from the weak Pulse, Coldness of the
Extremities, and the like, which constantly accompany it; And
consequently the _Moleculæ_ form'd by the Coagulation of the Animal
Juices must be larger, than these in the Small Pox, which proceed to the
ultimate Vessels before the Obstructions are formed. The _Measles_ are
another Confirmation of this Theory, whose _Moleculæ_ are still less
than the preceeding, as appears by their Eruption with greater Flatness,
and less Extension of the Obstructed Vessels. Thus also we see that in
all these Diseases where the Contagious Matter is more Virulent than
ordinary, or the Constitution of the Year more productive of these
Diseases, or join'd with a Hot Tense and Scorbutic Disposition,
Diarrhea's, Dysenteries, Purple Spots, Hemorrhages, Phrensies,
Convulsions, Inflammations, _&c._ equally accompany these as
Pestilential Diseases.

From what has been said in this and the foregoing Chapters may be
deduced the Reasons of the greater or less Virulency of the Small-Pox,
Measles, _&c._ in some Years more than others; As also why these
Diseases shou'd rage with the greatest Violence when join'd with, or
immediately preceeding a Pestilential Constitution of the Air. Hence
also appears the Reason why Pains of the Head, Stomach, Loins and Back,
preceed the Eruption of the Pustules, these Parts as nearest the Heart
being soonest obstructed, and the _Impetus_ of the Blood against the
obstructed Canals much greater than in the rest of the Body. As also why
the Pustules should appear so much sooner in the Face, Neck and Breast,
than other Parts of the Body, as appears from _Prop. 2_.

Hence likewise appears the Reason why the Fever, Vomiting, Pains, _&c._
preceeding the Eruption of the Pustules should cease or be much
diminish'd upon their Appearance; The _Moleculæ_, by the Force of the
Circulating Fluids, being driven into and fixt in the Cutaneous Glands,
and Secretory Vessels, whereby the Capillary Arteries being freed from
them, a more easy Passage is allowed to the Circulating Fluids. Hence
also appears the Reason why the Fever gradually increases with the
Augmentation of the Pustules, the Contiguous Vessels being compress'd by
their Distention, and the Obstructions in the Secretory Vessels made
more Numerous; whence the Quantity of the Perspirable Matter being
Diminished, and the Canals streightned, the Vessels will be more full,
and the Pulse more strong and frequent. Hence likewise it will follow,
that the more numerous the Obstructions are, and more pungent the
Contagious Matter, the more Violent the Symptoms will be, and the Matter
of the Pustules when suppurated become an Acrid and pungent gleety
Substance, or Laudable _Pus_. As also why the Time of Suppuration shou'd
vary in Proportion to the Virulency of the obstructing Matter; and
consequently the Reason of the Difference between the _Distinct_ and
_Confluent Small-Pox_. Hence also it will appear, that Bleeding, in the
Beginning of the Disease, ought only to be Administred where the
_Impetus_ of the Circulating Fluids is so great, that notwithstanding
the Diminution of the Force of the Blood by it, the protrusive Force of
the Circulating Mass will exceed the _Impetus_ made on the Obstructing
Matter by the Vibrations of the _Fibres_, and likewise why on its
imprudent Use in the Beginning of the Disease, the Pustules shou'd
disappear, and be driven back into the sanguineous Vessels. Hence also
may be deduced the Reason of the Flux by the Salival Glands, the
Swelling of the Face, Hands, and Feet, in the height of the Disease, the
Vessels being at this time Turgid by the Suppression of the perspirable
Matter; And likewise the Necessity of such Evacuations, as may reduce
the Pressure of the Fluids upon them to such a Proportion, as the Tone
of the _Fibres_ may be able to resist; And why where this is neglected,
a _Peripneumonia_, Phrensy, Delirium, _&c._ do frequently succeed.

_Lastly_, Hence may be deduced the Reason why the Small-Pox shou'd
rarely seize those twice, who have had a Competent Number of them. For
the Ultimate Perspirable Vessels being distended much beyond their
Natural Tone, by the Bulk of the Obstructing _Moleculæ_, the Secretory
Vessels must be left wider than before, and consequently less subject to
be obstructed by Particles of this Size; Agreeable to this is that
Observation of Dr. _Sydenham_ and others, That in those Constitutions of
the Air where the Small-Pox were very _Epidemic_, many (especially such
as attended the Sick) who before had been affected with this Disease,
were seized with a Fever in all Respects the same with that attending
the Small-Pox, except only the Eruption of the Pustules, and the
Symptoms which necessarily attend on them.



[Illustration]


                                  THE
                               APPENDIX.


[Illustration]

The Pressure of the Atmosphere on the internal Surface of the Lungs, as
computed in the foregoing Pages, so much exceeding that made by the
ingenious Dr. _Kiel_, in the last Edition of his Book of Animal
Secretion, it may not be amiss for the farther Illustration of it, to
show that the Weight computed by that Learned Author is not really the
whole Pressure of the Atmosphere, but the Force of the Lungs in
Expiration, by which they exceed the Pressure of the Air upon them. For
let the Tube A B be inserted into the Vessel C D E F of any given
Dimension, and both the Tube and Vessel fill'd with Water or any other
Fluid, it is evident from the Writers in Hydrostatics, that the Vessel C
D E F will be pressed upon on every Part of its Internal Surface equal
to the Basis of the Tube, by the Weight of a Column of the contained
Fluid of the same Height with the Fluid, and whose Base is equal to that
of the Tube, and consequently every Inch Square on the Internal Surface
of the Lungs will be pressed upon by a Column of Air, whose Height is
equal to that of the Atmosphere, and base one Inch Square, which will
amount to the aforesaid Sum. _Vide Pag._ 34 & 35. Now if we suppose the
Tube X inserted into the Neck of the Bladder Y and the Air forced into
the Bladder in Expiration, to an equal Density with that of the
incumbent Atmosphere, it is evident that the Air will not go out by the
Tube without some external Force, being in _Æquilibrio_ with the
Atmosphere, and consequently the Force by which it is expressed thro'
the Tube, must be that by which it exceeds the Pressure of the
Atmosphere, upon the Orifice of the Tube.

[Illustration]

If any one think that I have allowed too large a Quantity of Air to be
taken into the Lungs in an Ordinary Inspiration, That is sufficiently
recompensed by supposing the Diameter of the _Larynx_ equal to O.5 and
its Orifice O.19 which is more than it can be, for the Diameter does not
exceed O.4, and consequently its Orifice will be but O.12. Now it being
demonstrated by the Writers in Hydrostatics, that Weights forcing equal
Quantities of the same Fluid out of the same Orifice, are to each other
as the Squares of the Times in which the Fluid is forced out, and that
in equal Times and Quantities of the same Fluid forced thro' unequal
Orifices, the weights are Reciprocally as the Orifices; The Powers
forcing an equal Quantity of Air thro' the Orifices O.19 and O.12 must
be to each other in a Reciprocal Proportion, compounded of the Squares
of the Times and Orifices of the Tubes; Which will be found sufficient
to answer any Objection of this kind, by any who will give himself the
Trouble to compute it.


                                _FINIS._



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                           Transcriber Notes:

Passages in italics were indicated by _underscores_.

Small caps were replaced with ALL CAPS.

Throughout the document, the oe ligature was replaced with "OE".

Errors in punctuation, spelling, and hyphenation were not corrected
unless otherwise noted. Many of the spellings look strange by modern
standards, but then the rules for spelling changed since 1721.

Footnotes were moved to after the paragraph they were referenced in. The
footnote identifiers are the same as in the book, with the identifier
"s" being used twice,

On page 38, "Convnlsions" was replaced with "Convulsions".





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