Structure and Functions of The Body - A Hand-Book of Anatomy and Physiology for Nurses and others desiring a Practical knowledge of the Subject

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Title: Structure and Functions of The Body - A Hand-Book of Anatomy and Physiology for Nurses and others desiring a Practical knowledge of the Subject
Author: Fiske, Annette
Language: English
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[Illustration: The human skeleton (Lewis).]

STRUCTURE AND FUNCTIONS
_of_
THE BODY

A HAND-BOOK OF ANATOMY AND PHYSIOLOGY FOR
NURSES AND OTHERS DESIRING A PRACTICAL KNOWLEDGE
OF THE SUBJECT

BY
ANNETTE FISKE, A. M.

GRADUATE OF THE WALTHAM TRAINING SCHOOL FOR NURSES

_ILLUSTRATED_

PHILADELPHIA AND LONDON
W. B. SAUNDERS COMPANY
1911

PRINTED IN AMERICA

PRESS OF
W. B. SAUNDERS COMPANY
PHILADELPHIA

TO MY FATHER
and
TO DR. ALFRED WORCESTER

as those who have perhaps most helped me in
the formation and realization of my ideals
this book is affectionately dedicated

PREFACE.

Although there are already in existence many books on anatomy and
physiology for nurses, none with which I am acquainted has seemed to me
to provide in concise form just the knowledge needed by the nurse in
her profession. Most of them, moreover, separate the anatomy from the
physiology and all treat the different systems of tissues separately,
first the bones, then the muscles, and so on. These defects, as they
seem to me, I have attempted to correct not only by weaving the
physiology in with the anatomy, but by treating first the general
structures found throughout the body and then describing the structure
and function of each part in detail. Thus, the first chapter is devoted
to a description of the general structure of all the tissues, a
separate chapter being devoted, however, to the skin, its appendages,
and function, including the sense of touch. Then the head with its
bones, muscles, and organs of special sense is described, while the
brain is treated with the rest of the nervous system, thus forming the
connecting link between the head and the body. In the same way the
back, chest, abdomen, pelvis, and extremities are taken up in turn and
the bones, muscles, blood-vessels, nerves, and special organs of each,
together with their functions, described.

Although written more particularly for nurses I am in hopes that
this book may prove useful to any others who may desire to acquire a
practical knowledge of anatomy and physiology.

Besides the usual text-books, I am much indebted for material to notes
taken in lecture courses given by Dr. Fred R. Jouett and Dr. F. J.
Goodridge of Cambridge, Mass., at the Cambridge School of Nursing, and
by Dr. Vivian Daniel of Watertown at the Waltham Training School for
Nurses.

I wish particularly to express my gratitude and appreciation for the
kind and helpful criticism given me by Dr. Eugene A. Darling, Assistant
Professor of Physiology, Harvard College.

ANNETTE FISKE.
_May, 1911._

CONTENTS.

CHAPTER I.
PAGE
COMPOSITION AND GENERAL STRUCTURE OF THE BODY 11
Chemical Constitution of the Body, 11--The Cell, 12--The
Fundamental Tissues of the Body, 13--Epithelial
Tissue, 14--Connective Tissue, 15--Structure of Bone,
17--Bone Formation, 18--Chemical Composition of Bone,
18--Classification and Function of Bones, 19--Joints,
20--Muscle, 21--Action of the Muscles, 23--Physiology
of Muscle, 24--Cilia, 27--The Blood, 27--Arteries,
27--Veins, 28--Capillaries, 28--Lymphatic System,
29--Lymphatic Vessels, 31--Lymphatic Glands,
32--Lymph, 32--Glands, 35--Ductless Glands,
36--Nervous Tissue, 36.

CHAPTER II.
THE SKIN, ITS APPENDAGES AND ITS FUNCTION 39
The Skin, 39--Appendages of the Skin: Nails, 40--Hair,
40--Sebaceous Glands, 41--Sweat Glands, 42--Sweat,
42--Temperature Regulation, 43--Fever, 45--Sense of
Touch, 45--Touch Corpuscles, 46.

CHAPTER III.
THE CRANIUM AND FACE 48
The Cranial Bones, 48--Frontal Bone, 49--Parietal
Bones, 49--Occipital Bone, 50--Occipito-frontalis
Muscle, 51--Temporal Bones, 51--Sphenoid or Wedge
Bone, 52--Ethmoid Bone, 53--Turbinated Bones,
53--Ossification of Sutures, 53--Bones of the
Face, 53--Superior Maxillary Bones, 54--Antrum of
Highmore, 54--Malar or Cheek Bones, 54--Lachrymal
Bones, 54--Palate Bones, 54--Nasal Bones, 55--Vomer,
55--Inferior Turbinated Bones, 55--Inferior
Maxillary Bone or Lower Jaw, 55--Sublingual Gland,
56--Submaxillary Gland, 56.

CHAPTER IV.
THE ORGANS OF SPECIAL SENSE 57
The Nose, 57--The Sense of Smell, 58--The Mouth, 59--The
Hyoid Bone, 60--The Teeth, 60--The Sense of Taste,
61--Salivary Glands, 61--The Tonsils, 62--The Ear,
63--Eustachian Tubes, 63--Sensation of Hearing,
65--The Eye, 66--Lachrymal Gland, 68--Coats of the
Eye, 68--Light Rays and Sight, 70--Accommodation,
72--Color Perception, 73.

CHAPTER V.
THE NERVOUS SYSTEM 75
The Cerebrum, 75--The Cerebellum, 78--Pons Variolii,
78--Medulla Oblongata, 78--Spinal Cord,
79--Brain-centers, 81--Motor Tract, 82--Sensory
Tract, 82--Reflex Action, 83--Cranial Nerves,
83--Spinal Nerves, 84--Brachial Plexus, 85--Sacral
Plexus, 85--The Sympathetic System, 87--The
Sympathetic Nerves, 87.

CHAPTER VI.
THE BACK 88
The Spine, 88--The Vertebræ, 88--Muscles of the Neck,
92--Muscles of the Back, 93.

CHAPTER VII.
THE CHEST 96
The Sternum, 97--The Ribs, 97--Costal Cartilages,
98--Muscles of the Chest, 98--Diaphragm, 98--Mammary
Glands, 100.

CHAPTER VIII.
THE HEART AND CIRCULATION 101
The Heart, 101--The Pericardium, 101--Cavities of the
Heart, 103--The Endocardium, 103--The Valves of
the Heart, 103--Circulation, 105--Circulation in
the Fetus, 106--Arteries, 107--Veins, 109--Portal
Circulation, 109--Pulmonary Circulation, 110--Nerves
of the Heart, 110--Heart Sounds, 111--The Heart
Beat, 111--Factors Affecting Circulation, 112--The
Pulse, 113--Blood Pressure, 114--Nerve Supply of the
Blood-vessels, 115--The Blood, 116--Composition
of the Blood, 116--Coagulability of the Blood,
117--Blood-corpuscles, 118.

CHAPTER IX.
THE LUNGS AND RESPIRATION 121
The Larynx, 121--The Trachea, 123--The Thyroid Gland,
124--The Thymus Gland, 124--The Bronchi, 125--The
Lungs, 125--The Pleura, 125--The Mediastinum,
126--Respiration, 127--Air, 129--Respiratory
Sounds, 129--Changes in Air in Lungs, 129--Effect
of Respiration on Blood, 130--Nervous Mechanism of
Respiration, 130--Variations in Respiration, 131.

CHAPTER X.
THE ABDOMEN AND THE ORGANS OF DIGESTION AND EXCRETION 132
The Abdominal Cavity, 132--Muscles of the Abdomen,
132--The Peritoneum, 134--Abdominal Regions,
134--Salivary Digestion, 136--The Pharynx, 139--The
Esophagus, 138--The Stomach, 138--Gastric Digestion,
139--Vomiting, 140--Intestinal Canal, 141--The Small
Intestine, 142--Intestinal Digestion, 143--Absorption
in Intestine, 144--The Large Intestine, 145--Food and
Metabolism, 147--The Liver, 149--The Gall-bladder,
152--The Pancreas, 153--The Spleen, 153--The
Suprarenal Capsules, 154--The Kidneys, 155--The
Urine, 156--The Ureters, 159--The Bladder and
Urethra, 159.

CHAPTER XI.
THE PELVIS AND THE GENITAL ORGANS 161
The Pelvis, 161--The Male Generative Organs, 164--The
Prostate Gland, 164--The Testes, 165--The Penis,
165--The Female Generative Organs, 165--The Ovaries,
165--The Fallopian Tubes, 166--The Uterus, 167--The
Vagina, 168--The External Genitalia in the Female,
169--The Vulva, 169--The Mons Veneris, 169--The Labia
Majora, 169--The Labia Minora, 170--The Clitoris,
170--The Meatus Urinarius, 170--The Hymen, 170--The
Fourchette, 170--The Perineal Body, 170--The
Perineum, 170.

CHAPTER XII.
THE UPPER EXTREMITIES 171
The Shoulder Girdle, 171--The Clavicle, 171--The Scapula,
173--Shoulder Muscles, 174--The Humerus, 175--Upper
Arm Muscles, 176--The Ulna, 177--The Radius,
178--The Wrist, 180--The Hand, 181--Meta-carpals,
181--Phalanges, 181--Muscles of the Forearm,
182--Muscles of the Hand, 184--Joints of the Upper
Extremity, 185--Blood Supply of the Upper Extremity,
185--Nerves of the Upper Extremity, 186.

CHAPTER XIII.
THE LOWER EXTREMITIES 187
The Femur, 187--Thigh Muscles, 189--The Patella,
192--Joints of the Lower Extremity, 192--The Tibia,
194--The Fibula, 194--The Ankle, 195--The Foot,
195--Metatarsals, 195--Phalanges, 195--Muscles of the
Leg, 196--The Blood Supply of the Lower Extremity,
198--Nerves of the Lower Extremity, 199.

INDEX 201

STRUCTURE AND FUNCTIONS OF THE BODY.

CHAPTER I.

COMPOSITION AND GENERAL STRUCTURE OF THE BODY.

Anatomy is the study of the physical structure and physiology the study
of the normal functions of the human body.

=Chemical Constitution of the Body.=--In the body only twenty elements
have been found. These include carbon, oxygen, hydrogen, nitrogen,
sulphur, phosphorus, calcium, magnesium, manganese, chlorin, potassium,
and fluorin. For the most part they appear in very complex and highly
unstable combinations, though oxygen and nitrogen may be said to exist
uncombined in the blood, alimentary canal, and lungs. Hydrogen also
occurs in simple form in the alimentary canal, but as the result of
fermentation, not as an element of the body.

Of the organic compounds some contain nitrogen and some do not. The
most important of the former are the proteins, which are found only in
living bodies and consist of carbon, hydrogen, oxygen, nitrogen, and
sulphur combined in very similar proportions. The important proteins in
the body are the serum albumen and fibrin found in the blood, myosin in
muscle, globulin in the red blood-corpuscles, and casein in the milk.
Similar to the proteins but capable of passing through membranes are
the peptones, the final result of protein digestion, from which the
albuminoids differ in that they contain no sulphur. Ferments containing
nitrogen exist in all the cells of the body, though more particularly
in those of the digestive organs, and the coloring matters, as the
bilirubin of the bile, are nitrogenous.

The organic substances that do not contain nitrogen are the
carbohydrates or starches, the hydrocarbons or fats, and the acids, of
which the most important is carbon dioxide, given off by the lungs.

The inorganic substances are water, which forms a large percentage of
all the tissues and from one-fourth to one-third of the whole body
weight, sodium chloride or common salt, which plays an important part
in keeping substances in solution, potassium and magnesium chloride,
and hydrochloric acid, found in the stomach.

=The Cell.=--Although the body is a very complex organism, the cell
is its unit or foundation. In fact, the body begins life as a single
protoplasmic cell, the ovum, which is frequently compared to the
amœba, a microscopic animal consisting of a single cell of protoplasm
or living substance--a substance not well understood as yet--but
possessing practically all the functions of the human body. For,
although it has no organs and is homogeneous in structure, the amœba
can move by throwing out a process, and can surround and absorb food,
which it builds up into new tissue, discarding the waste. The ovum,
however, differs from the amœba in that it has a transparent limiting
membrane and contains a darker spot, the nucleus. This in turn contains
another smaller spot, the nucleolus, while through the protoplasm,
which is semi-fluid, extends a fine network that seems to hold it in
place.

The _ovum_ is very small, about ¹/₁₂₅ inch in diameter, and after
fertilization grows by segmentation, the nucleus dividing in two and
the protoplasm grouping itself anew about the two nuclei. This division
continues, each cell dividing and forming two, or sometimes four,
new cells, all of which at first appear alike. By degrees, however,
differentiation takes place and different groups of cells assume
different characteristics. Thus the various tissues are gradually
developed, each with a structure and a function of its own, and are
distributed among the various organs, each organ consisting of several
tissues. During the process of growth and even after full growth of the
body is attained old cells are continually dying and being replaced by
new ones.

The typical cell is circular, but through being squeezed together
in the tissues or for some other reason the cells vary in shape in
different parts, being at times hexagonal, spindle-shaped, or columnar.
Yet, whatever their differences in shape or other characteristics, they
all live the same sort of life. All protoplasm absorbs oxygen when it
comes in contact with it and in the process of combining with it is in
part burned or oxidized, with the consequent setting free of heat and
other forms of energy and the formation of carbon dioxide. So long as
the body is alive, therefore, whether it is in a state of activity or
of rest, it is the seat of constant chemical change throughout all its
cells, and to these chemical changes are due all the forms of energy
manifested by the body. For energy is never destroyed, though it may
appear in a different form, and the elements of the human body are
so combined that their energy may be liberated and manifested in the
different functions the body exhibits.

=The fundamental tissues of the body= are the epithelial tissues, the
connective tissues, including the cartilaginous and bony tissues, and
the muscular and nervous tissues. Of these the epithelial tissues serve
as a protection to the surface of other tissues; the connective tissues
together form a framework for the support and general protection of the
other tissues; while energy is expended by muscular and nervous tissue,
the latter directing the former in its movements. All the tissues are
inter-dependent and the organs work together. Besides cells every
tissue contains a certain amount of lifeless matter, the intercellular
substance, which was at some time produced by the cells.

[Illustration: FIG. 1.--Epithelium: 1, pavement epithelium; 2, columnar
epithelium; 3, ciliated epithelium; 4, stratified epithelium.]

In =epithelial tissue= there is little intercellular substance, the
cells being close together and arranged generally as a skin or membrane
covering external or internal surfaces. When there are several layers
of cells, the deepest are columnar in shape and the others become
more and more flattened and scale-like as they approach the surface,
where they are gradually rubbed off and replaced by the growth of new
cells from below. This stratified epithelium, as it is called, is
found wherever a surface is exposed to friction, as in the skin and
in the mucous membrane of the mouth, pharynx, and esophagus, and in
that of the vagina and the neck of the uterus. In simple epithelium,
where there is only a single layer of cells, the cells may be pavement
or hexagonal, columnar, glandular, or ciliated, according to their
different functions. The flat pavement cells occur where a very smooth
surface is required, as in the heart, lungs, blood-vessels, serous
cavities, etc. None of these surfaces communicate directly with the
external surface of the body and the name endothelium is substituted
for epithelium. The columnar form of cell in the intestine facilitates
the passage of leucocytes between the cells. In glandular epithelium
the cells vary according to the gland in which they occur, their
protoplasm being filled with the material the gland secretes. Finally,
ciliated epithelium is composed of columnar cells with cilia or little
hair-like processes upon their free surface which serve to send
secreted fluids and other matters along the surfaces where they occur,
as in the air passages, parts of the generative organs, the ventricles
of the brain, and the central canal of the spinal cord.

=Connective tissue= has a great deal of intercellular substance. One
form, _areolar tissue_, is composed of a loose network of fine white
fibers with a few yellow elastic fibers interspersed and with cells
lying in the spaces between the fibers. It connects and surrounds the
different organs and parts, holding them together, yet allowing free
motion, and is one of the most extensively distributed of the tissues.
It is continuous throughout.

[Illustration: FIG. 2.--Section of bladder epithelium. (Hill.)]

Closely allied to the areolar is the _fibrous tissue_, in which the
white fibers lie close together and run for the most part in one
direction only. This is found in ligaments, joints and tendons, as also
in such fibrous protective membranes as the periosteum, dura mater, the
fasciæ of muscles, etc. Fibrous tissue is silvery white in appearance
and is very strong and tough, yet pliant. It is not extensile.

_Elastic tissue_, on the other hand, has a large predominance of
yellow elastic fibers and is very extensile and elastic, though not so
strong as the fibrous. It is found in the walls of the blood-vessels,
especially the arteries, in the walls of the air tubes, in the
ligaments of the spine, etc.

_Fatty or adipose tissue_ is formed by the deposit of fat in the cells
of the areolar tissue and is found in most parts where the areolar
tissue occurs, though it varies largely in amount in different parts.
It is found pretty generally under the skin, fills in inequalities
about various organs and about the joints, and exists in large
quantities in the marrow of the long bones. In moderate amounts it
gives grace to the form and constitutes an important reserve fund.

[Illustration: FIG. 3.--Adipose tissue (Leroy): _a_, Fibrous tissue;
_b_, fat cells; _c_, nucleus of fat cells; _d_, fatty acid crystals in
fat cells.]

_Cartilage_ consists of groups of nucleated cells in intercellular
substance. It is very firm, yet highly elastic, and serves in the
joints to break the force of concussion of the harder and less elastic
bones. Except when it occurs at the end of a bone, it is covered with
a membrane called the perichondrium, which carries its blood supply.
In the nose, ear, larynx and trachea it serves to give shape, to keep
the passages open, and to afford attachment for muscles. Most of the
skeleton of the fetus consists of cartilage, which later develops into
bone.

_Bone._--In bone the intercellular tissue is rendered hard by the
deposit of mineral salts, the resulting material being of great
strength and rigidity. The texture may be close and dense like ivory or
open and spongy, the difference lying merely in the fact that the one
has fewer spaces between the solid particles than the other. There is
usually a hard, compact layer on the exterior of the bone, as that is
where the greatest cross-strain comes, especially in the long bones,
while within is the cancellous or spongy tissue, which gives lightness
to the bone and is capable of withstanding enormous pressure, though it
can bear little cross-strain.

[Illustration: FIG. 4.--Cross-section of compact bone tissue. (After
Sharpey.)]

=Structure of Bone.=--The hard substance in bone is always arranged
in lamellæ or bundles of bony fibers, which in cancellous tissue
meet to form a kind of lattice-work, while in the dense tissue they
are generally arranged in rings about the Haversian canals, channels
through which the blood-vessels pass through the bone longitudinally.
Between the lamellæ are spaces called _lacunæ_, in which lie branched
cells, the spaces being connected with each other and with the
Haversian canals by numerous tiny canals or canaliculi, by which
nutrient material finds its way from the Haversian canals to all parts
of the bone.

Within the bone is the medulla or _marrow_, which is of two varieties:
the yellow, which is largely fat and is found in the long bones of
adults, and the red, which is nearly three-fourths water and is found
in most of the other adult bones and in the bones of the fetus and of
the infant.

Lining the medullary and cancellous cavities is a delicate connective
tissue lining, the _endosteum_, which contains many bone-forming cells,
while on the outside of the bone, except at the articular ends, is the
_periosteum_ with its outer protective layer and its inner vascular
layer containing osteoblasts or bone-forming cells. The periosteum is
essential for the growth of new bone where the old bone has died, and
if the periosteum is removed from healthy bone the part beneath is
liable to die, as it is by the constant growth of the osteoblasts that
the bone grows and is renewed. In the repair of broken bones tissue is
formed between and around the broken ends.

=Bone Formation.=--Most of the skull and face bones begin as
membranes of connective tissue, that is, are formed in membrane.
Bones are also formed in cartilage, the bone formation in this case
beginning from centers of ossification, where the deposit of lime
salts in the intercellular substance begins, the salts coming to the
centers dissolved in the plasma. Such a center of growth in a bone
is called the epiphysis and is separated from the main part of the
bone or diaphysis by cartilage until full growth is attained, when
ossification becomes complete. So in surgery, in working on the bones
of children, part of the epiphysis should always be left for the sake
of future growth. The outer shell of compact tissue is deposited by the
periosteum.

=Chemical Composition of Bone.=--Chemically bone is composed of about
one-third organic or animal matter, largely gelatine, and two-thirds
inorganic matter, including various salts of calcium, magnesium, and
sodium. In young children the animal matter predominates and the bones
are soft and often bend instead of breaking, only the outside shell on
one side giving way, as in “green-stick” fracture. In rickets there is
a deficiency of lime salts, but the increased brittleness of the bones
in old age is due, not to increase of mineral matter, but to the less
spongy texture of old bones.

=Classification and Function of Bones.=--There are in the body some
two hundred bones, which may be classified as long, short, flat, and
irregular. Occasionally an irregular bone develops in a fontanelle, the
membranous opening at the juncture of the sutures of the skull. This
is known as a Wormian bone. It is not, however, included in the two
hundred, as are not the sesamoid bones or bones developed in tendons,
with the exception of the patella or knee-cap.

Long bones are developed in cartilage and consist of a shaft, two
extremities, and various processes. They are more or less curved to
give them strength and grace. They serve as supports and act as levers
for purposes of motion and the exercise of power. Since a hollow
cylinder is just as strong as a solid one of the same size, the weight
coming only on the outer shell, the great bones which are accountable
for weight and which need to be light themselves have hollow shafts,
composed chiefly of compact tissue with a central medullary canal. The
ends, however, are expanded in order to make better connection at the
joints and to afford broad surfaces for muscular attachment, cancellous
tissue being used in them for lightness and strength. The large spongy
ends also give elasticity and lessen jar, and by bringing the tendons
to the bone at a greater angle increase their effectiveness. Blood is
brought to the long bones not only by the vessels of the periosteum but
by the medullary artery, which penetrates the compact tissue by the
nutrient foramen and divides into an ascending and a descending branch.

Short bones are spongy throughout. They are used for strength and where
little motion is required.

Flat bones are composed of two thin layers of compact tissue with a
varying amount of cancellous tissue between, and are for protection and
muscular attachment. The cancellous material between the two layers or
tablets of the skull is called the diploë.

Eminences and depressions occur on bones and when they are not
articular are for the attachment of ligaments and muscles. If they are
articular, they help to form joints.

As a whole the bony framework serves to keep the soft parts in place,
to support and protect them, and to aid in locomotion. The bones of the
head and trunk support and protect organs; those of the arms are for
tact and prehension; those of the lower extremities are for support and
locomotion.

Normally bones have little sensibility, but when inflamed they are
extremely sensitive and painful.

=Joints.=--The bones are connected with and move upon one another by
means of joints. These joints are of three kinds: 1. Immovable, where
the adjacent margins of the bones are closely applied, with little
fibrous tissue between, as in the sutures of the head; 2. those with
limited motion, which are very strong, the parts being connected with
tough fibro-cartilage; and 3. freely movable. In this last group the
articulating surfaces are covered with cartilage, which again is
lined with a delicate synovial membrane which secretes a small amount
of lubricating fluid, the synovial fluid, to reduce friction. Their
surfaces are also sometimes deepened by the presence of inter-articular
fibro-cartilages. Bursæ or sacs of synovial membrane occur outside the
joints under tendons and ligaments to reduce friction.

The nature and extent of the motion of a joint is defined and the bones
are held together by strong bands of fibrous tissue or ligaments, these
ligaments being more fully developed in joints where there is great
freedom of motion or where there is great weight to be supported. In a
ball-and-socket joint, such as the hip, there is a ligament in the form
of a strong capsule which surrounds the joint on all sides and limits
its motion, while hinge joints, like the elbow, and pivot joints, such
as that formed by the atlas on the axis, have lateral ligaments that
allow of freer motion. In the shoulder-joint, which is the most freely
movable joint in the body, the capsular ligament is very lax.

In general the kinds of motion possible in joints may be said to be
flexion, extension, abduction, adduction, circumduction, and rotation.

When much violence is applied to a joint and no dislocation results, as
in a sprain, there is often much stretching and even laceration of the
ligaments.

=Muscle.=--The flesh, which forms a large proportion of the weight of
the body, consists of muscular tissue. Of this two kinds are found:
1. The striated or striped muscle of animal life, which is under the
control of the will and so is known as voluntary muscle, and 2. the
unstriped or smooth muscle of organic life over which we have no
control, that is, the involuntary muscle. Each fiber of striped muscle
has an elastic, membranous sheath, the sarcolemma, and consists of
rod-shaped cells with a nucleus along the edge, set end to end and
having crosswise striations. In unstriated muscle the fibers, which
have no sarcolemma, consist of oval or spindle-shaped cells, with
a nucleus much smaller than that of striped muscle and situated in
the middle. In both kinds of muscle the fibers are bound together
with connective tissue and blood-vessels into fasciculi or bundles,
and many bundles go to make up a muscle. The muscle in turn has a
connective tissue envelope or sheath, the fascia. These fasciæ are
found throughout the body, the superficial ones being just beneath
the skin, while the deep ones not only form sheaths for the various
muscles but form partitions between them and serve to strengthen their
attachments. The striped muscles are those of motion, while the
unstriped occur in the hollow organs, surrounding the cavity and in
some cases lessening its capacity by their contraction.

An intermediate form of muscle known as cardiac muscle occurs in the
heart. Here the fibers have striations but the nucleus is generally in
the middle of the cell and the fibers branch and run together.

[Illustration]

[Illustration: FIG. 5.--Voluntary muscle (Leroy). _A_, Three voluntary
fibers in long sections: _a_, three voluntary muscle fibers; _b_,
nuclei of same; _c_, fibrous tissue between the fibers (endomysium);
_d_, fibers separated into sarcostyles. _B_, Fiber (diagrammatic): _a_,
dark band; _b_, light band; _c_, median line of Hensen; _d_, membrane
of Krause; _e_, sarcolemma; _f_, nucleus. _C_: _a_, Light band; _b_,
dark band; _c_, contracting elements; _d_, row of dots composing the
membrane of Krause; _e_, slight narrowing of contracting element aiding
in production of median line of Hensen.]

In life muscle appears more or less translucent and is contractile and
alkaline, but in death it loses its translucency and becomes rigid,
at the same time giving off in decomposition much carbon dioxide, so
that its reaction is acid. This phenomenon of the muscles becoming
rigid in death is called rigor mortis and occurs generally a few hours
after death, though it may come at once or be considerably delayed.
It may last anywhere from a few moments to several days but generally
lasts from twenty-four to thirty-six hours. It is probably due to the
formation in the muscle of myosin, a substance which probably comes
from myosinogen in the living muscle and which is closely akin to
the fibrin of blood. Probably the myosin or what precedes it causes
clotting of the muscle just as fibrin or what precedes it causes
clotting of the blood.

[Illustration: FIG. 6.--Three voluntary muscle fibers from an injected
muscle, showing network of blood capillaries. (Hill.)]

The muscles vary in shape in different parts of the body, being long
and slender in the limbs and broad and flat in the trunk. They are
attached chiefly to bones but also to cartilages, ligaments, and skin,
either by means of tendons, which are cords or bands of white inelastic
fibrous tissue, or by means of aponeuroses, membranous expansions of
the same nature. Most voluntary muscles consist of a belly and two ends
or tendons. The origin is the fixed point from which it acts while the
movable point upon which it acts is known as its insertion.

=Action of the Muscles.=--When attached to bones, muscles are
distributed in three ways: 1. When it is necessary to produce much
motion rapidly, a short muscle is used. 2. When a part needs to be
moved far and much contraction on the part of the muscle is, therefore,
needed, the muscle is very long, as in the case of the sartorius
muscle, which shortens half its length. 3. Finally, where less distance
has to be covered but greater power is required, tendons are used, as
in this case the contraction is powerful but does not carry the part
far.

In performing the mechanical work of the body the muscles are aided by
the fact that the bones, to which they are largely attached, are set
together loosely and form a set of levers, on which the muscles act
to perform certain definite acts. All three classes of levers occur:
1. where the fulcrum is between the weight and the power, as in the
case of the head, which is balanced by the muscles of the neck on the
vertebræ; 2. where the weight is between the fulcrum and the power, as
when a person raises himself upon his toes; and 3. where the power is
between the fulcrum and the weight, as when the biceps is used to raise
a weight held in the hand. The erect position of the body is difficult
to maintain because the center of gravity is high up, and it is by the
contraction of many muscles in the legs, thighs, back, abdomen, and
neck that the body is balanced upright upon the feet.

=Physiology of Muscle.=--_Irritability_ or sensitiveness to stimulation
and _contractility_ or the power to contract are the two most important
functions of muscle. Contraction occurs in response to nervous energy
brought by the nerves, a nerve filament going to each muscle fiber,
into which it plunges, its substance being lost and its sheath
becoming continuous with that of the muscle fiber. Any irritant,
as heat, electricity, etc., when applied to the nerve, causes the
muscle to contract. Moreover, muscle has an irritability of its own
and can contract independently of the nervous system. In contracting
it shortens and thickens, bringing the two ends closer together, and
becomes firm and rigid. The amount of contraction depends upon the
strength of the stimulus and the irritability of the muscle. The
minimal stimulus is the least stimulus that will cause a contraction
and the maximal is one that will cause the greatest contraction. The
work done depends in like manner upon the strength of the stimulus.
During contraction certain sounds are given off called muscle sounds,
which can be heard with the stethoscope but have no special
significance.

The muscles which have the greatest power of rapid contraction are
generally attached to levers. Indeed, striated muscle is characterized
by the rapidity and strength with which it works, though its rhythmic
motion is slight. Smooth muscle, on the other hand, is characterized
by its great force, considerable rhythm, considerable tone, and slight
rapidity, that is, its contraction is slower and lasts longer than that
of striated muscle. Cardiac muscle is characterized by great rhythm and
force, fair rapidity, and slight tonicity, tonicity being the amount of
tone or readiness to work. For even in sleep muscle is always in tone,
that is, ready to do its work. It is this that makes the difference in
appearance between a living and a dead person and enables one to spring
to his feet at night if he hears a noise, a thing he could not do if
his muscles were wholly relaxed. Thus, rapidity is the great function
of striated, tonicity of smooth, and rhythm of cardiac muscle. In
paralysis the muscles droop and lose their tone. Muscles are frequently
the seat of rheumatic disorders.

When set free, potential energy accomplishes work. In muscle there is
a good deal of potential energy, which is set free as heat and as work
accomplished. Even when the muscles are at rest, chemical changes are
going on and heat is being produced, though more heat is produced when
they are functioning. If the body depended upon its gross motions for
all its heat it would grow cold while a person rested. The respiratory
organs, however, and the heart are always working and chemical changes
are constantly taking place.

Ordinarily a muscle has some object in contracting, such as the raising
of a load, and it contracts voluntarily more or less according to
the weight of the load. The amount of work done is calculated in
foot-pounds or gram-meters, that is, the energy required to raise one
pound one foot or one gram one meter. As a rule the muscles with the
longest fibers, as the biceps, do the most work and those with a large
number of fibers do more than those with less. It has been calculated
that whereas an engine gives back one-twelfth of the energy of the coal
consumed, muscle liberates one-fourth of the energy brought to it in
the form of food. During activity the glycogen or sugar in the muscle
is used up and the muscle becomes more acid, owing to the lactic acid
that is formed. The carbon is taken in and carbon dioxide given off.
Nitrogen puts the muscle in condition to do its work but is not so
much used up in the work as is the carbohydrate material. So it is the
non-nitrogenous matter that does the work and any increase in urea, the
end-product of protein metabolism, is mere wear and tear.

Sudden heat or cold causes muscular contraction and moderate heat
favors both muscular and nervous irritability. Moderate cold, however,
lessens the force of contraction and below zero muscle very largely
loses its irritability without necessarily becoming rigid.

While well supplied with blood, muscle will contract without fatigue,
but if the blood supply is shut off, it soon loses its irritability
and becomes rigid. The more a muscle is used in moderation the more it
develops, but after it has done a certain amount of work it becomes
exhausted, losing its irritability or power to respond to stimuli
and later becoming rigid. Such fatigue is due to the production of
certain poisonous waste products which have a paralyzing effect on the
nerves and which are ordinarily gradually carried away in the blood,
but which sometimes, if produced to excess, accumulate too fast for
the blood wholly to remove them. Usually the nerve becomes exhausted
first and the muscle substance later. So long as it is connected with
the nervous system a muscle will respond to stimuli, but when the
nerve becomes tired, degeneration is more rapid. In fact, the degree
of exhaustion is determined by several factors, as by relation to the
central nervous system, variations in temperature, blood supply, and
functional activity, the process being more rapid in warm than in cold
blooded animals.

=Cilia.=--A few motions are accomplished by tissue that is not
muscular, as in the case of the cilia attached to the cells of the
respiratory tract, which lie flat on the free surface and then lash
forward, serving in the air cells to keep the air in motion and in the
tubes to send secretions from below upward and outward and to keep out
foreign bodies. Cilia are also found in the female genital tract, where
they aid the passage of the ovum from the ovary to the womb. They act
together, though apparently not governed by the nervous system. As in
the white corpuscles of the blood, whose motion also is not muscular,
the changes that take place in ciliated epithelium are probably about
the same as those in muscular tissue, that is, contractile.

=The Blood.=--To most of the tissues just described nourishment is
brought in the blood, which circulates through the body in a system
of hollow tubes, the arteries and veins, whence it is distributed
through the agency of the lymphatic system. There are no blood-vessels,
however, in the epidermis, epithelium, nails, hair, teeth, nor in the
cornea of the eye. The vessels that carry the blood from the heart
are called arteries, those that return it veins. The former begin as
large vessels and gradually decrease in size; the latter begin as small
vessels and form larger and larger trunks as they approach the heart.

The _arteries_ have three coats: 1. a thin, serous coat, the internal
or intima; 2. a middle or muscular coat, and 3. an external coat of
connective tissue. The middle coat is the thickest and is the one that
prevents the walls from collapsing when cut across. Except in the
cranium, each artery is enclosed in a sheath with its vein or veins,
the venæ comites. Usually the arteries occupy protected situations and
are straight in their course. Where a vessel has to accommodate itself
to the movements of a part, however, it may be curved, as in the case
of the facial artery which is curled on itself to allow for movements
of the jaw. They anastomose or communicate freely with one another,
thus promoting equality of distribution and pressure and making good
circulation possible even after the obliteration of a large vessel.

The _veins_ have three coats like the arteries, but they are not so
thick and the muscular coat is not so highly developed, so that the
walls collapse when cut and have no elasticity. There are constrictions
on the surface of many of the veins due to the presence of valves.
These valves are formed of semilunar folds of the lining membrane
and are arranged in pairs. They serve to prevent the blood, whose
circulation in the veins is sluggish, from flowing back.

There are two sets of veins, the superficial and the deep, which
communicate with each other. In fact, all the veins, large and small,
anastomose very freely, especially in the skull and neck, where
obstruction would result in serious trouble, throughout the spinal
cord, and in the abdomen and pelvis. The deep veins accompany the
arteries in their sheath, while the superficial ones have thicker walls
and run between the layers of the superficial fascia under the skin,
terminating in the deep veins. In the skull the venous channels take
the form of sinuses, formed by a separating of the layers of the dura
mater, with an endothelial lining that is continuous with that of the
veins.

The _capillaries_ are intermediate between the arteries and the veins,
the final division of the arteries and the first source of the veins.
They are tiny vessels with but a single coat, continuous with the
innermost coat of both arteries and veins and consisting practically of
one layer of cells with a small amount of connective tissue between.
They spread in a great network throughout the tissues, forming plexuses
and being especially abundant where the blood is needed for other
purposes than local nutrition, as in the secreting glands. Their
diameter is so small that the red corpuscles have to pass in single
file and may even then be squeezed out of shape. As they have no
muscular tissue in their walls, they have no power of contracting.
Their walls, however, like those of the smaller arteries and veins, are
porous and by virtue of this quality they play an important part in the
economy, since in them the exchange takes place between the tissues and
the blood.

The arteries in general carry freshly oxidized blood and the veins
blood from which the oxygen has been largely used up and which contains
waste material. In the pulmonary system, however, the case is reversed,
the pulmonary arteries conveying venous blood, as it is called, from
the heart to the lungs to be oxidized and the veins returning the blood
after it has received its new supply of oxygen.

The pumping of the blood through the arteries is assisted by the
contractions of the muscular coat, while the elastic tissue, of which
it contains a certain amount, gives elasticity to the walls and enables
them to stretch and so to accommodate the larger blood supply forced
into them at each beat by the heart. The walls of the veins have not
the power of contracting and the blood is pushed through more by
gravity and the action of the arteries than by any action of their own.

The walls of all the vessels are nourished by tiny blood-vessels in
the outer coat, known as _vasa vasorum_, and the nerves that regulate
the action of the arteries are the vasomotor nerves from the vasomotor
center in the medulla. Sufficient impulse goes from this center to the
blood-vessels all the time to keep them somewhat contracted, in a state
of tone, that is, which is increased or diminished as the blood supply
is to be diminished or increased.

=Lymphatic System.=--The lymphatic system also extends throughout
the body and consists of a system of channels, spaces, and glands
very closely related to the circulatory system and containing a fluid
called lymph. There are three principal parts to the system: 1. the
lymph spaces, which are open spaces, with no definite walls, in the
connective tissue framework of the body, more frequent near arteries
and veins and especially so among the capillaries; 2. the lymph
capillaries or small vessels which connect the lymph spaces; and 3. the
lymphatic vessels, of which there is a deep and a superficial set, the
latter accompanying the superficial veins on the surface of the body,
the former accompanying the deep blood-vessels.

[Illustration: FIG. 7.--Diagram showing the course of the main trunks
of the absorbent system: the lymphatics of lower extremities (D) meet
the lacteals of the intestines (LAC) at the receptaculum chyli (R.C.),
where the thoracic duct begins. The superficial vessels are shown in
the diagram on the right arm and leg (S), and the deeper ones on the
left arm (D). The glands are here and there shown in groups. The small
right duct opens into the veins on the right side. The thoracic duct
opens into the union of the great veins of the left side of the neck
(T). (Yeo.)]

The _lymph spaces_ are generally small, though there are some large
serous cavities, such as the abdomen, that may be considered as
extended lymph spaces.

[Illustration: FIG. 8.--Diagram of a lymphatic gland, showing afferent
(_a. l._) and efferent (_e. l._) lymphatic vessels; cortical substance
(_C_); medullary substance (_M_); fibrous coat (_c_); sending trabeculæ
(_tr_) into the substance of the gland, where they branch, and in the
medullary part form a reticulum; the trabeculæ are surrounded by the
lymph path or sinus (_l. s._), which separates them from the adenoid
tissue (_l. h._). (Sharpey.)]

The _lymphatic vessels_ have delicate, transparent walls, with three
coats like the arteries, though much thinner, and anastomose even
more freely than the veins. They have a beaded appearance due to
the presence of numerous valves, which form constrictions on their
surface. The right lymphatic duct, which is only about an inch long,
drains all the lymphatics of the right half of the upper part of the
trunk, the head, and the neck approximately, while the thoracic duct
drains those of the rest of the body. The latter, which is the largest
vessel of the system, begins opposite the second lumbar vertebra
with a bulb-like reservoir for the lymph or chyle, the receptaculum
chyli, and extends up along the spinal column for a distance of
about eighteen inches to the seventh cervical vertebra, where, with
the right lymphatic duct, it empties into the left subclavian vein
at its junction with the internal jugular, thus establishing direct
communication between the lymph spaces and the venous system. The
orifices of both vessels are guarded by semilunar valves to prevent
regurgitation of the blood.

[Illustration: FIG. 9.--Central (superficial) lymphatic glands of the
axilla. (After Leaf.)]

The _lymphatic glands_ are small oval glandular bodies and occur here
and there along the course of the lymphatics. Before entering one of
them the vessel breaks up into several afferent vessels which form
a plexus within and then emerge again as several efferent vessels
which soon unite to form one trunk. These glands occur chiefly in the
mesentery, along the great vessels, and in the mediastinum, axilla,
neck, elbow, groin, and popliteal space.

The _lymph_ varies in character with the locality, being a little
thicker and more opalescent in the lacteals, as the lymphatics of the
small intestine are called, especially during digestion, when fat is
present. Here it is called chyle. Otherwise it is generally a clear,
transparent and slightly opalescent fluid, which, owing to the presence
of fibrin, clots when drawn from the body and allowed to stand. In
fact, it resembles blood plasma very closely in composition and, as it
also contains a certain number of corpuscles or leucocytes that just
correspond to the white corpuscles of the blood, it is practically
blood without the red corpuscles. These leucocytes have considerable
power of amœboid movement and are thought by some to play an important
part in the absorption of food.

Owing to intracapillary pressure, the lymph transudes into the
lymph spaces and bathes the tissues, being carried away again by
the lymphatics. The amount of transudation is determined by the
blood pressure--the greater the pressure, the greater the amount of
transudation--and is increased by some organic action of the cells in
the walls of the vessels. In the process of transudation a certain
amount of solid matter goes through the wall of the vessel and it is
probable that certain protein elements can be carried thus from the
blood-vessels to the lymphatics, though they do not pass through the
capillary wall as readily as other substances. Some lymph is also
probably formed by the action of the tissues themselves, though the
process is not understood.

All muscular movements, active or passive, including the respiratory
movements, tend to drive the lymph on its way by pressure, the valves
of the vessels keeping it from flowing back. Moreover, its flow is
from the capillaries to the veins or from a region of high pressure to
one of less pressure. There is probably also some contraction in the
walls of the vessels themselves, and the continual formation of lymph
helps to drive it along. If an obstruction to the circulation occurs,
however, back-pressure results and causes too great transudation. In
that event a limb becomes swollen, pale, and generally cool. It pits
on pressure, the pressure driving the lymph out and there being no
circulation to bring it back. This condition is called œdema and occurs
in liver, kidney, and heart troubles, being generally first observed at
the ankles. In ascites, hydrothorax, hydrocephalus, and pericardial and
pleural effusions the fluid corresponds to lymph in its composition and
the large amount is due to excessive formation of the fluid, which is
normally present in small quantities.

Lymph gives the tissues substances from the blood that they need and
carries off those they do not, whether waste or substances of use to
other tissues. Because they thus absorb certain materials not needed
by the tissues and convey them to the circulation, the lymphatics have
also been called absorbents. Indeed, lymph may be spoken of as the
middleman between the blood and the tissues.

Another function of the lymph is to lubricate. Thus, the synovial fluid
of the joints is lymph and the pleuræ and the pericardium contain lymph
or serum to reduce the friction between the adjoining surfaces as much
as possible. The brain and spinal cord do not quite fill the cavities
of the cranium and the spinal column but float on a cushion of lymph,
the cerebro-spinal fluid. When the brain, which is subject to increase
and diminution in size, increases in size, it drives the lymph out, and
when it diminishes, the lymph returns.

The lymph glands serve as a protection to adjacent parts and when it
leaves the gland the lymph is purer and richer in leucocytes than
when it entered. In fact, they filter harmful matter from the lymph
and apparently also form white corpuscles. Normally they can with
difficulty be felt, but in disease, if the leucocytes are unable to
destroy or carry off the poison, the lymph carries it along to the
glands, which swell and become tender. If the infection is not severe
the swelling goes down and the tenderness passes after a short time,
but if it is severe, there may be suppuration and abscess formation
and the gland even perhaps be destroyed, giving its life for the
health of the part. Thus a wound in the foot, if infected, may cause
irritation and enlargement of the glands at the knee and in the groin.

The lymphatic glands are frequently the seat of tubercular infection,
especially in the neck, and are enlarged in scarlet fever, tonsillitis,
and diphtheria. In syphilis there is general glandular enlargement, and
the glands in the groin become enlarged in all diseases of the genital
organs. In malignant growths, such as cancer, the extension of the
disease is often along the lines of the lymphatics.

=Glands.=--Of glands in general a word might now be spoken. They are of
two kinds, excreting and secreting, and, when simple, are formed by the
folding in of a free surface, as in the case of the salivary, gastric,
and sebaceous glands, the cells at the gland becoming so modified as to
be able to perform the function of excreting or secreting. In racemose
glands the gland is broken up into many pockets. Excreting glands take
from an organ or from a part substances which have outlived their
usefulness and are to be cast out of the body, while the secreting
glands form from the blood substances that did not exist in it before,
but which are of use to the body, as the ptyalin of the saliva. A
strict line cannot, however, be drawn between the two kinds of glands,
most glands partaking more or less of both functions, though the
sebaceous and sweat glands are probably purely excreting glands and
the salivary glands are almost purely secreting. The glands, moreover,
are more or less interchangeable in their functions, that is, they
have vicarious function, and one gland can take up and do for another
what that other is for some reason unable to do. In jaundice, where
there is stoppage of the bile duct, the kidneys help out the liver by
excreting the bile. If one kidney is removed the other does work for
both, and the glands of the skin may help out the kidneys or _vice
versa_. Hemorrhage from the lungs sometimes occurs in suppression of
the menses.

In a general way the _function of glands_ is chemical. They filter out
by osmosis, selecting the useful parts for secretion and the useless
for excretion. In the chemical action that goes on considerable energy
is given off, as is shown by the amount of pressure in the glands and
by the fact that their temperature is higher than that of the blood.
They all work in a reflex manner, being under the control of the
central nervous system. Thus, what is eaten affects the nerve terminals
in the mouth, the sensation passes to the nervous system, and an
impulse is carried by the motor nerves to the salivary glands.

Most of the glands have ducts to convey away their secretion to other
parts of the body or to send excretions out of the body, but there are
also _ductless glands_, which, though they seem to have some important
function in the process of metabolism, are not well understood. Most
of them seem to manufacture some substance that is absorbed by the
tissues and that plays an important part in the bodily metabolism,
though nothing is secreted by them externally. They are said to have
an internal secretion, whereas the glands with ducts have an external
secretion. The liver has both forms of secretion, the bile which is
sent out and the glycogen that is stored. The ductless glands are the
thymus and thyroid glands, the suprarenal capsules, and the pituitary
body in the brain.

=Nervous Tissue.=--Presiding over all the organs, muscles, and
blood-vessels, as the source of all action and all sensation, are the
nerves. Nervous tissue is of two kinds: 1. the gray or vesicular, which
originates impulses and receives impressions, and 2. the white or
fibrous, which conveys impressions. The gray matter consists of large
granular cells of protoplasm containing nuclei, which give off many
branches or dendrites. From the under surface there usually comes one
main branch, the axis-cylinder process. These processes sometimes give
off branches and sometimes not, but they form the nerve fibers and
carry impulses away from the nerve cells. The cells of the processes
are elongated in shape, have a nucleus, and are placed end to end, with
a definite constriction between them.

Each axis-cylinder process is surrounded by a sheath called the
medullary sheath, while each nerve fiber consists of a central
axis-cylinder process surrounded by the white substance of Schwann
and enclosed in a sheath. A bundle of these fibers invested in a
fibro-areolar membrane called the neurilemma constitutes a nerve, and
of these the white matter is formed. The blood supply is brought by
minute vessels, the _vasa nervorum_.

[Illustration: FIG. 10.--Longitudinal nerve fiber (diagrammatic): _a_,
Axis-cylinder; _b_, medullary sheath; _c_, neurilemma; _d_, nucleus;
_e_, node of Ranvier. (Leroy.)]

The nerves of the cerebro-spinal system preside over animal life and
have to do with voluntary acts, while those from the sympathetic
system regulate organic life and are quite independent of the will.
Both sensory and motor nerves extend all over the body, accompanying
the arteries in a general way. The sensory nerves end on the surface
in plexuses, in end bulbs situated in the papillæ of the skin, or
in tactile corpuscles, these last occurring more especially where
there is no hair. The motor nerves end peripherally in plexuses or
by end plates. The central terminations of the motor nerves and the
terminations of sensory nerves in special organs, except where they end
in a cell, are not well understood.

Like muscles, nerves are probably never at rest, for through them the
muscles get their tone. When a nerve acts, no heat is produced and
there is no change in the nerve afterward, as there is in muscle.
Probably nerve impulse is the transmission of physical rather than
chemical changes along the fiber, the atoms of the nerve being set
in vibration and the vibrations being transmitted along its length.
Stimulation is produced by physical injury, by chemical influence, by
electricity, by heat, and the message is always referred to the nerve
termination. Thus, if the nerve at the elbow, over the “crazy bone,” is
touched, a tingling is felt in the fingers rather than at the point of
pressure. A person who has had an arm or leg amputated will frequently
speak of his fingers or toes on that side being cold, or complain of
pain in them, because the scar below the point of amputation tightens
around the nerves and pinches them.

It is through the nerves that people get in touch with the outer world
and that they judge of size, weight, etc. All careful adjustment of the
muscles is under the control of the nervous system.

CHAPTER II.

THE SKIN, ITS APPENDAGES AND ITS FUNCTION.

The whole exterior surface of the body is covered by the skin, an
excreting and absorbing organ, which serves as a protection to the
parts beneath and is also the organ of touch. It has two layers,
a superficial and a deep. The superficial layer, the epidermis or
cuticle, is composed wholly of epithelial cells, of which the deepest
layer is columnar and moulded upon the papillary layer of the derma,
while the intermediate layers are more rounded and the surface ones
flat. The deepest layer also contains the skin pigment, which causes
the variation in shade between the Indian, the negro, and the white
man. Below the epidermis, which is chiefly protective, is the tough,
elastic, and flexible tissue of the derma or true skin, in which are
vested most of the activities of the skin. Its surface is covered
with papillæ, which are more numerous in the more sensitive parts.
Each papilla contains one or more capillary loops and one or more
nerve fibers, while some terminate in an oval body known as a tactile
corpuscle. Beneath the papillæ is the reticular layer, composed of
interlacing bands of fibrous tissue and containing blood-vessels,
lymphatics, and nerves, as well as unstriped muscle fibers where hair
is present.

[Illustration: FIG. 11.--Vertical section of skin.]

At the apertures of the body the skin stops and is replaced by _mucous
membrane_, an integument of greater delicacy but which consists
fundamentally of the same two layers, a superficial, bloodless
epithelium and a deep fibrous derma. It is continuous with the skin,
but is much redder and more sensitive and bleeds more easily. The
passages and cavities that it lines, unlike those lined by serous
membranes, communicate with the exterior of the body and are for that
reason protected against contact with foreign substances by mucus,
which is thicker and more sticky than the lymph that moistens the
endothelium found on serous surfaces. Mucous membrane is found in the
alimentary canal, the respiratory tract, and the genito-urinary tract.
In cavities, like the stomach and intestines, which are subject to
variations in capacity, it is thrown into folds or rugæ. The mucus is
secreted by small glands in the membrane.

=Appendages of the Skin.=--The skin has various appendages. On the
dorsal surface of the last phalanges of the fingers and toes are
flattened and horny modifications of epithelium, the _nails_. They have
a root embedded in a groove of skin by which they grow in length and a
vascular matrix of derma beneath them which gives growth in thickness.
To their growth in length there seems to be no limit.

The _hairs_ also, which occur all over the body, except on the palms
of the hands and the soles of the feet, are a modification of the
epithelium. Each hair has a bulbous root springing from an involution
in the epidermis and derma called the _hair follicle_, into which one
or two sebaceous glands empty. It is raised by involuntary muscle
fibers and grows by constant additions to the surface by which it is
attached. This growth seems, however, to be limited, and when its term
is reached the hair falls out and is replaced by another. The horny
epithelial cells that go to form the hair contain the pigment that
gives it its color.

[Illustration: FIG. 12.--Skin and longitudinal section of hair: _a_,
Epidermis; _b_, corium; _c_, sebaceous gland; _d_, fibrous root-sheath;
_e_, glassy membrane; _f_, outer root-sheath; _g_, inner root-sheath;
_h_, expanded bulbous end of hair; _i_, papilla of hair; _j_, arrector
pili; _k_, adipose tissue. (Leroy)]

Like the hairs, the _sebaceous glands_ are situated in all parts of
the body except the palms of the hands and the soles of the feet. They
lie in the papillary layer and empty into the hair follicles, except
occasionally, when they empty directly upon the surface of the skin.
They secrete an oily substance, _sebum_, the débris resulting from the
degeneration of the epithelial cells of the gland itself, which serves
to keep the hair glossy and the skin soft and flexible.

The _sweat glands_, on the other hand, are more frequent on the palms
and soles and though sometimes found in the derma are usually situated
lower down in the subcutaneous cellular tissue. They are least numerous
on the back and neck. Coiled up in the lower layers of the skin, they
discharge the sweat through a spiral excretory duct upon its free
surface.

The _sweat_ is a clear, colorless, watery fluid with a salty taste,
an alkaline reaction, and a characteristic odor that varies with
the individual. If very scanty, it may be acid in reaction. Besides
water it contains a small percentage of solids, as inorganic salts,
especially sodium chloride, fatty acids, neutral fats, and at times,
especially in some diseases of the kidneys, urea, that is, the
end-products of the metabolism of starches and fats chiefly. There
is usually also some carbon dioxide, whence the expression cutaneous
respiration.

The sweat serves to keep the skin moist and in good condition, to
remove outworn and poisonous or irritating matters, and to regulate
the temperature. As a rule it evaporates upon reaching the surface, in
which case it is known as invisible or insensible perspiration, but if
conditions of the atmosphere are not favorable to prompt evaporation,
as when the air is damp, the skin becomes damp and there is visible
perspiration.

Though an abundant supply of blood increases the action of the sweat
glands, they are regulated by definite secretory nerves rather than
by the vasomotor nerves. In a cold sweat the action is probably due
to some disturbance of the nerve supply without increase of the blood
supply. Ordinarily perspiring is a reflex act due to the stimulation
of the afferent cutaneous nerves, as by the application of heat, but
sometimes, as in cases of strong emotions, involuntary impulses are
sent from the brain to the spinal centers and so arouse the action
of the glands. Atropin has the power of preventing the secretion of
sweat by paralyzing the terminations of the secretory nerves, while
pilocarpin produces an opposite effect in a similar way.

On account of these sweat glands the skin becomes next in importance
after the kidneys in the excretion of waste products. The quantity of
sweat excreted varies greatly and is hard to measure. It is influenced
by the temperature and humidity of the surrounding air, by the nature
and quantity of food and drink consumed, by the amount of exercise,
the relative activity of other organs, especially the kidneys, and by
certain mental conditions. The hotter it is, the greater the amount of
perspiration. In damp weather there may be less perspiration, but it
does not evaporate and is therefore more in evidence.

Ordinarily man has a temperature of 98.6°. The source of this body heat
or temperature is the general body metabolism, muscular activity, and
activity of the glands, especially of the liver, which is constantly
active, the blood in the hepatic vein being warmer than that in any
other part of the body. The tissue of the brain also is said to be
warmer than the surrounding blood, and the heart and respiratory
muscles, which are in constant activity, are responsible for much of
the body heat. The amount of heat generated in the body, therefore,
varies at different times, according as a person is awake or asleep,
quiet or active.

=Temperature Regulation.=--The temperature is regulated by variations
in the production and loss of heat, less being known of its production
than of its loss. It has been calculated that four-fifths of the energy
of the body is converted into heat, one-fifth into work. As the minimum
amount of heat produced in twenty-four hours is sufficient to raise 10
gallons of water from 0° to boiling-point, it is evident that if there
were not some way for the escape of much of this heat the body would
become hotter and hotter and finally destroy itself. The temperature,
however, except on the surface, is uniform, heat being lost as fast
as it is produced. For, although oxidation at any point raises the
heat of the blood at the point, this heat is carried by the blood to
other parts, to which the surplus is given up, while blood cooled in
the skin goes to the hotter inward parts to cool them and be warmed
itself. In fact, heat is expended by conduction and radiation, through
respiration, perspiration, and heat given to the urine and fæces. It
is, therefore, largely, 75 to 80 per cent., carried off through the
skin and the lungs; 60 to 70 per cent. is lost by radiation to the
air and other bodies with which the body comes in contact; 20 to 30
per cent. is lost by the evaporation of sweat, 4 to 8 per cent. by
the warming of expired air, urine and feces, and 1 to 2 per cent.
by cold food that is taken in. Radiation acts more favorably where
the surroundings are cool and the air in motion, as on a breezy day.
Conduction is carried on best where the surrounding air is cool,
especially if it is moist, for moist air is a better conductor of heat
than dry air. Evaporation is very important in hot weather or where men
work in hot air.

Even in health the temperature may range from 98.6° to 99.5°, and a
degree or two below or above is not dangerous. When a person first
gets up in the morning his temperature is apt to be subnormal, but
after food and exercise have been taken it becomes normal and stays
so till the end of the day, when, if the person is tired, it may go
up a little. If a person is tired out, the temperature is apt to be
subnormal. There is also in the body what is called the vital tide,
which is highest afternoon and evening and lowest in the morning.

The rate of production of heat varies greatly in different people. One
person uses a certain amount of tissue more quickly than another, that
is, he lives faster. Moreover, size makes a difference in that a small
body has more surface to its weight than a large one and so has to
produce the same amount of heat at a faster rate in order to maintain
the right temperature. Taking food increases heat, probably because
of the muscular effort needed to eat it. Muscular work is another
factor. And finally the whole matter of heat production seems to be
under the control of the nervous system. Not much is known on this
point except that there is a heat center in the medulla which plays an
important part in heat production and whose influence is seen where
the temperature shoots way up in disease just before death. It is now
thought that fever is due to a disturbance of this nervous mechanism,
though just what the disturbance is is not known.

_Fever_ is a condition of increased bodily temperature, due to
increased production or to decreased loss of heat. As a rule, in all
fevers the metabolic changes in the body are increased. Hence the
patient becomes emaciated in a long fever. The frequent increase in the
amount of urea during fever shows an increase in protein metabolism.
The temperature in fevers rises as high as 106° and in sunstroke
sometimes to 110°. Except in sunstroke a higher temperature than 106°
generally means death. Subnormal temperature is due to a decrease in
the bodily metabolism and so to lessened heat production. As a rule,
if the functions are all active, especially that of the sweat glands,
a person can be exposed to severe heat without the temperature being
affected, though sometimes on a hot summer day it may be up half to one
degree. The cause of heat-stroke with its high fever is unknown, but
probably it is due to some effect on the heat center in the brain. Heat
prostration is also due to prolonged exposure to heat, but is generally
accompanied by a subnormal temperature. The effect of cold, as in
freezing, is to diminish all the metabolic activities of the body. The
temperature can be artificially regulated more or less by variations of
food, varying amounts of exercise, by drugs, etc.

=Sense of Touch.=--Before passing on to a discussion of the individual
parts, a few words might well be said of the sense of touch, since that
is general and resides largely in the skin, whose other functions have
just been described. It may be regarded as the form from which all
the other special senses have developed, certain portions of the body
having become more sensitive than others to certain vibrations, as the
eye to those of light. The internal organs probably have little sense
of touch.

[Illustration]

[Illustration: FIGS. 13, 14.--Meissner’s corpuscle from man; ×750.
(Böhm, Davidoff, and Huber.)]

Touch is useful only within arm’s reach but there gives one a sense of
space that sight does not give. It is practically determined by the
_touch corpuscles_, which are found in the skin over almost the entire
body, though they are more numerous in some places than in others,
the distribution of the corpuscles determining the sensitiveness of
the skin. These touch corpuscles are protoplasmic bodies containing
nuclei, about which are entwined filaments from the cutaneous nerves.
Where the corpuscles are absent the filaments of the cutaneous nerves
themselves play an important part. The finger tips have a very delicate
sense of touch and the tip of the tongue is the most sensitive part of
the body. Hence spaces in the mouth seem larger than elsewhere. By
the transmission of sensations of touch to the brain the sensation is
localized and the tactile sensation becomes a tactile perception.

There are three main divisions of the sense of touch: 1. sensations of
touch proper or tactile sensation; 2. sensations of temperature, and
3. sensations of pain. The temperature sense is the transmission by
the skin of sensations not so much of a certain degree of heat or cold
as of the difference between the temperature of an object and that of
the skin. The longer an object is in contact with the skin, the less
conscious the person is of it, not only because it becomes of the
same temperature, but also because he becomes accustomed to it. There
also seem to be in the skin, besides the touch corpuscles, two other
terminal organs with separate nerve fibers, the one for detecting heat,
the other cold; for there are places on the body where heat can be
detected and cold cannot, and _vice versa_.

Sensations of pain may be merely an exaggeration of tactile sensation,
as in too hard pressure or too great heat, but there seems to be also
a sensation of pain in the skin. All organs are said to have common
sensibility to pain and any exaggeration of this sensibility causes a
sensation of pain. All the special senses require a certain amount of
judgment in the interpretation of the sensations they convey.

CHAPTER III.

THE CRANIUM AND FACE.

The intelligence and all the special senses, except the sense of touch
already spoken of, are gathered together compactly in the head, where
they are carefully protected with bony tissue. Covering the brain is
the skull or cranium, which is made up of eight bones, the frontal, the
occipital, two parietal, two temporal, the sphenoid, and the ethmoid,
while the bones of the face are fourteen in number, two nasal, two
superior maxillary, two lachrymal, two malar, two palate, two inferior
turbinated, the vomer, and the inferior maxillary. For the most part
the bones are arranged in pairs, one on either side.

=The Cranial Bones.=--The cranium or skull is especially adapted for
the protection of the brain and the bones are flat and closely fitted
to its surface. They have two layers of bone, the outer and the inner
tables, of which the outer is the thicker, and between these is a
tissue filled with blood-vessels, the _diploë_. In the infant, whose
brain has not yet attained its full size, opportunity must be left
for growth and the skull therefore consists of a number of bones with
interlocking notched edges, where growth takes place, but in the adult
it forms one solid covering of bone.

The line where the edges of two cranial bones come together is called
a _suture_. The suture between the frontal bone and the forward edges
of the two parietal bones is called the _coronal suture_, that between
the two parietal bones at the vertex of the skull is known as the
_longitudinal_ or _sagittal suture_, and that between the occipital
bone and the back edges of the parietal bones as the _lambdoidal
suture_.

Where the coronal and sagittal sutures meet is a membranous interval
known as the _anterior fontanelle_, while the _posterior fontanelle_
is at the juncture of the sagittal with the lambdoidal suture. These
fontanelles--so called from the pulsations of the brain that can
be seen in them--close after birth either by the extension of the
surrounding bones or by the development in them of small bones known
as _Wormian bones_, the posterior one closing within a few months,
the anterior by the end of the second year. In rickets, however, the
anterior fontanelle remains open a long time, sometimes into the fourth
year.

[Illustration]

[Illustration: FIG. 15.--Cranium at birth, showing sutures and
fontanelles.]

The =frontal bone=, as its name implies, forms the fore part of the
head or forehead. It joins the parietal bones above and the temporal
bones on either side. At the lower edge are the supra-orbital arches,
each with a supra-orbital notch or foramen on its inner margin for
the passage of the supra-orbital vessels and nerve, the nerve most
affected in neuralgia. Just above the arches on either side are the
superciliary ridges, behind which, between the two tables of the skull,
lie the frontal sinuses. On the inner surface the frontal sulcus for
the longitudinal sinus runs along the median line.

The =parietal bones= are the side bones of the skull. They meet each
other in the sagittal suture at the median line above and join the
frontal and occipital bones at either end, while below they touch upon
the temporal bones, the temporal muscles being attached in part along
their lower surface. These muscles are inserted into the coronoid
process of the lower jaw, which they thus help to raise and to retract.

[Illustration: FIG. 16.--Front view of the skull. (After Sobotta.)]

The =occipital bone= is at the base of the skull and at birth consists
of four pieces. In the lower, anterior part is the foramen magnum, an
oval opening through which the spinal cord passes from the skull down
into the spinal canal. Half way between the foramen and the top of the
bone is the external occipital protuberance for the attachment of the
ligamentum nuchæ which holds the head erect. The inner side of the bone
is deeply concave and is divided by a cross-shaped grooved ridge into
four fossæ, the internal occipital protuberance being situated where
the arms of the cross meet. The occipital lobes of the cerebrum lie in
the two upper fossæ and the hemispheres of the cerebellum in the two
lower ones. In the grooves upon the ridge are the sinuses which collect
the blood from the brain.

The occipital and frontal muscles, united by a thin aponeurosis, cover
the whole upper cranium and are known as the _occipito-frontalis
muscle_. At the back this is attached to the occipital bone, while
in front it interlaces with various face muscles. It is a powerful
muscle and raises the brows, wrinkles the forehead, and draws the scalp
forward. Long hair grows on the skin over it as a further protection
against blows upon the skull and sudden variations in temperature.

The =temporal bones=--said to be so named because the hair over them
is the first to turn with age--are situated at the sides and base of
the skull and are in three portions: the squamous or scale-like, the
mastoid or nipple-like, and the petrous or stony portion. The squamous
is the upper portion and has projecting from its lower part the long
arched zygomatic process, which articulates with the malar bone of the
face and from which arises the _masseter muscle_, one of the chief
muscles of mastication, which has its insertion in the ramus and angle
of the lower jaw. Just above the zygomatic process the _temporal
muscle_ has its origin in part, while below is the _glenoid fossa_ for
articulation with the condyle of the lower jaw, the posterior portion
of the fossa being occupied by part of the parotid gland.

The rough mastoid portion of the temporal bone is toward the back and
affords attachment to various muscles, of which the most important are
the occipito-frontalis and the sterno-cleido-mastoid. Within it are the
mastoid cells, which communicate with the inner ear and are lined with
mucous membrane continuous with that of the tympanum. They probably
have something to do with the hearing. In children they often become
the seat of inflammation (mastoid abscess) in infectious diseases and
the mastoid bone has to be cut to let out pus that has collected.
As the lateral sinus is directly behind the mastoid bone, there is
very great danger of going through into the sinus and causing a fatal
hemorrhage.

[Illustration: FIG. 17.--Side view of the skull. (After Sobotta.)]

The petrous portion, which contains the organ of hearing, is between
and somewhat behind the other two portions, at the lower edge of the
temporal bone, wedged between the sphenoid and the occipital bones. On
its outer surface is the _external auditory meatus_, and from below
projects a long sharp spine called the _styloid process_, to which
several minor muscles are attached. In the same angle between the
petrous and squamous portions lies the bony Eustachian tube.

The =sphenoid= or =wedge bone=, so called because in the process of
development it serves as a wedge, lies at the base of the cranium,
forming as it were the anterior part of the floor of the cavity
containing the brain. It is a large, bat-shaped bone and articulates
with all the cranial and many of the facial bones, binding them all
together. It has a body, two large wings, and two lesser wings and,
appears on the outside of the skull between the frontal and the
temporal bones behind the zygomatic process. In the adult the body of
the sphenoid is hollowed out into the sphenoid sinuses, in which pus
sometimes forms.

=The Ethmoid Bone.=--In front of and below the sphenoid and extending
forward to the frontal bone is the ethmoid, the last of the cranial
bones. It consists of a horizontal cribriform or sieve-like plate, from
either side of which depend lateral masses of ethmoid cells. To the
inner side of these masses are attached the thin curved _turbinated
bones_, superior and middle, while between them is a vertical plate
that forms the bony septum of the nose. Rising from the upper surface
of the cribriform plate is another vertical plate, the _crista galli_,
with the olfactory grooves on either side for the reception of the
olfactory bulbs, filaments of the olfactory nerve passing down through
the perforations of the cribriform plate to the nose. For the brain,
which fills almost the entire cavity of the cranium, is supported
by the sphenoid and ethmoid bones internally, as it is protected
externally by the other cranial bones.

=Ossification of Sutures.=--If premature ossification of all the
sutures occurs, _idiocy_ results, while in _cephalocele_ there is a gap
in the ossifying of the bones so that the membranes or brain protrude.
In _rickets_ the forehead is high and square and the face bones
poorly developed, so that the head looks larger than it really is. In
_Paget’s disease_ the bones enlarge and soften. This affects the head
but not the face and often the first thing noticed is that the hat is
too small. _Craniotabes_ is thinning of the bone in places, the bone
becoming like parchment and being easily bent. It is generally caused
by pressure of the pillow or the nurse’s arm.

=Bones of the Face.=--The facial bones serve to form the various
features of the face, which after all are merely organs of special
sense. Many delicate muscles control the facial expression which,
consciously or unconsciously, reflects the character of their owner.

Surgically the most important of the facial bones are the two _superior
maxillary bones_, because of the number of diseases to which they
are liable. They meet in front, together forming the upper jaw, and
with the malar bone help form the lower part of the orbit of the eye.
They are cuboid in shape and are hollowed out into a pyramidal cavity
called the _antrum of Highmore_, which opens by a small orifice into
the middle nasal meatus and which sometimes becomes infected and has
to be tapped. The nasal process for articulation with the frontal and
nasal bones has, at its lower edge, a crest for the inferior turbinated
bone, and close beside this on the inside, extending down from the
upper edge, is a deep groove which, with the lachrymal and inferior
turbinated bones, helps to form the lachrymal canal for the nasal tear
duct. The bones give attachment to many small muscles, connected for
the most part with the nose and mouth, of which the masseter is the
only important one.

The two _malar_ or _cheek bones_ are small quadrangular bones, which
form the prominences of the cheeks and help form the orbits of the
eyes. Projecting backward from each is a zygomatic process for
articulation with the zygomatic process of the temporal bone, while a
maxillary process extends downward for articulation with the superior
maxillary. Here again the most important muscle attached is the
masseter. If the malar bone is crushed great deformity results.

The _lachrymal bones_ are two small bones, about the size and shape of
a finger-nail, situated at the front of the inner wall of the orbit. At
the external edge is a groove which lodges the lachrymal sac above and
forms part of the lachrymal canal below.

The two _palate bones_ are at the back of the nasal fossæ and help to
form the floor of the nose, the roof of the mouth, and the orbit. Each
has a vertical and a horizontal plate, and it is these last that by
their juncture form the _hard palate_. Oftentimes in cases of hare-lip
_cleft palate_ also occurs, the result of incomplete development. To
remedy the consequent opening in the roof of the mouth, which makes
articulation difficult, operation is generally resorted to, though
sometimes a plate is fitted over the opening by a dentist.

The _nasal bones_ are two small oblong bones which articulate with the
frontal and superior maxillary bones and with each other. They form the
bridge of the nose, the rest of the nose being wholly of cartilage,
except for the _vomer_, a bone shaped like a plough-share, which forms
part of the nasal septum, articulating along its anterior edge with the
ethmoid and the triangular cartilage.

The two _inferior turbinated bones_ lie along the outer walls of the
nasal fossæ. They are thin scroll-like bones covered with mucous
membrane and serve to heat the air as it passes in. Sometimes when one
has a cold, the membrane and the bone too swell up and close the nares.
Loss of the sense of smell in a bad cold may be due to such swelling
and the consequent impeding of the entrance of odoriferous particles--a
condition that would likewise interfere with the sense of taste. Part
of the bone is sometimes removed, to enlarge the passage, enough being
left to warm the air.

Lastly, there is the _inferior maxillary bone_ or _lower jaw_. This
has a horseshoe-shaped body and two _rami_, one at either end. Each
ramus has a pointed process in front called the _coronoid process_,
into which is inserted the temporal muscle. At the back, and separated
from the coronoid process by the sigmoid notch, is the _condyle_, which
articulates with the glenoid fossa on the temporal bone. The rami also
give attachment to the masseter muscle at its point of insertion. In
adult age the ramus is almost vertical but in old age the portion of
the jaw hollowed out into alveoli for the teeth becomes absorbed and
the angle of the jaw becomes very obtuse. On the inner side of the jaw
near the middle on either side is the fossa for the _sublingual gland_,
while the _submaxillary gland_ lies in a fossa farther back on either
side.

Sometimes the lower jaw is dislocated and when once this has occurred
it is liable to occur again, the ligaments becoming stretched.

CHAPTER IV.

THE ORGANS OF SPECIAL SENSE.

=The Nose.=--The nose, the organ of the sense of smell, is composed
of a framework of bones and cartilages, the bridge being formed by
the two nasal bones, and the septum by the vomer and the triangular
cartilage. It consists of two parts, the _external nose_ and the
internal or _nasal fossæ_, which open to the face by the anterior nares
or nostrils and into the pharynx by the posterior nares. Externally it
is covered with skin, internally with ciliated mucous membrane. The
_fossæ_ have the inferior turbinated bones along their outer walls and
are divided into three parts known as the _superior_, the _middle_, and
the _inferior meatus_, the middle one connecting with the antrum of
Highmore, while into the inferior meatus the lachrymal canal empties.
There are many small muscles of which little use is made, although in
forced respiration, as in pneumonia, where every aid to breathing is
called into play, even the alæ nasi or nostrils are made to exert what
muscular power they possess in order to supply more air.

[Illustration: FIG. 18.--The nasal cavity. (After Sobotta.)]

Not only is most of the air breathed in through the nose and warmed in
its passage through, but the nose is the organ of smell and by means
of the peculiar property of its nerves protects the lungs against
deleterious gases and helps the taste discriminate. The _olfactory_
or _first cranial nerves_, after emerging from the brain, lie on the
under surface of the frontal lobe and rest on the ethmoid bone in what
is known as the _olfactory tract_. Each nerve ends in a bulb-like
termination called an _olfactory bulb_, which rests on the cribriform
plate and sends little terminal fibers down through to be distributed
to the nasal cavities, especially to the upper half of the septum of
the nose, the roof of the nose, and the anterior and middle turbinated
bones. For in the mucous membrane of the upper nasal cavity are
specially modified epithelial cells called _olfactory cells_, which
play an important part in the conduction of smell. Hence when one
wishes to smell anything especially well he sniffs it up.

Probably the _sensation of smell_ is caused by odoriferous particles
in the atmosphere being breathed into the nose, where they affect the
olfactory cells, which transmit the impulses to the olfactory nerve
and so to the brain. Whereas a certain amount of moisture in the nasal
cavity seems to be essential for accuracy of smell, the presence of
too much or too little interferes with it. The mucous membrane has a
certain power also of distinguishing different smells at the same time,
though this power varies greatly in different people, one smell often
wholly overpowering all others.

The cartilage below the bridge of the nose is sometimes attacked
in _syphilis_ and _cancer_, and _lupus_ often begins on the nose.
_Deviation of the septum_ may occlude all air from one side of the
nose, an effect also produced by _polypi_, generally of the turbinated
bone. Either condition is easily remedied. _Nosebleed_, though
generally unimportant, may be serious in adults.

=The Mouth.=--The mouth is of great importance as an entrance for fresh
air to the lungs when the nasal passages are for any reason impeded
and as the resonant chamber from which proceeds the voice, man’s
chief means of communication with his fellows. Its chief value may be
said, however, to reside in the fact that it is the vestibule of the
alimentary canal. It is an ovoid cavity lined with mucous membrane and
is bounded in front by the _lips_, at the sides by the _cheeks_, below
by the floor and tongue, and above by the _hard palate_ anteriorly and
by the _soft palate_ posteriorly, the _uvula_ depending from the latter
like a curtain between the mouth and the pharynx. Shape is given to the
mouth by the bones of the upper and lower jaw and its size is altered
by the lowering and raising of the latter, which is quite freely
movable.

[Illustration: FIG. 19.--The hyoid bone. (Toldt.)]

At the back of the mouth, at the entrance to the pharynx, are the
_anterior_ and _posterior pillars_ of the fauces, which contain
muscular tissue, and between which on either side are thick masses
of lymphoid tissue, the _tonsils_. The floor of the mouth is formed
largely by the _tongue_, which completely fills the space within the
lower teeth. Its base or root is directed backward and downward and is
attached by muscles to the hyoid bone and the lower jaw, the _hyoid
bone_ being a horseshoe-shaped bone lying just below and as it were
within the inferior maxillary. The base of the tongue is attached also
to the epiglottis and at the sides to the soft palate by the anterior
pillars. Except at its base and the posterior part of its under surface
the tongue is free, but a fold of mucous membrane, the _frenum_, holds
it somewhat in front. Thus it possesses great versatility of motion and
serves as an auxiliary in articulation, mastication, and deglutition.

=The Teeth.=--Securely embedded in either jaw are the teeth, nature’s
instrument for the first preparation of the food for digestion through
tearing and grinding. The _incisors_, which are in front, have wide
sharp edges for cutting the food. Next come the _canine_ teeth with a
sharp point for tearing it, while at the back are the _molars_ with a
broad flat top for grinding.

There are two sets of teeth: 1. the _temporary_ or _milk teeth_,
twenty in number--four incisors, two canines, and four molars in
each jaw--which appear at from six months to two years, and 2. the
_permanent teeth_, thirty-two in number--four incisors, two canines,
known as _eye teeth_ in the upper jaw and as _stomach teeth_ in the
lower jaw, four bicuspids, so called because they have two cusps where
the molars have four or five, and six molars in each jaw--which come
from the sixth to the twenty-first years. The first to appear are the
two lower middle incisors, which come at the age of six months. The
last to appear are the _wisdom teeth_, the farthest back of the molars,
which come at the age of twenty-one years or thereabouts.

Each tooth consists of a crown or body above the gum, a neck, and a
fang or root within the gum. The body is of dentine or ivory with a
thin crust of enamel and contains the _pulp_, a vascular connective
tissue containing many nerves. Beginning at the neck and covering the
fang is a layer of cement or true bone.

=The Sense of Taste.=--The sense of taste lies chiefly in the _taste
buds_ as they are called which are filled with _gustatory cells_
and are found in the papillæ of the tongue, principally in the
_circumvallate papillæ_ at the back of the tongue, which are few in
number and arranged in a V-shape. There is also a certain power of
taste in the tip and sides of the tongue but little in the upper
surface or dorsum. Only five special tastes can be distinguished:
bitter, sweet, acid, sour, and salt, but sometimes more than one
can be distinguished at a time, as bitter and sweet. Every one can
distinguish between different tastes but the power varies in different
people and with different conditions. Certain tastes seem to be better
distinguished in certain places, as sweet at the tip and bitter at the
back of the tongue. Moreover, the sense of taste is very dependent
upon the sense of smell, especially in the case of aromatic and savory
substances, which one really does not taste but smell. If one held his
nose and closed his eyes he would not know from the taste whether he
was eating onion or apple. This leads to the habit of pinching the nose
when taking nauseous medicines.

To be tasted a substance must be in solution. Friction against the
tongue, lips or cheek increase the sense of taste. A temperature of
100° Fahrenheit favors taste, while both great heat and great cold
impair it.

There are probably at least two nerves of taste, the lingual branch
of the trifacial or fifth cranial and the gustatory branch of the
glosso-pharyngeal.

Along with the sense of taste there are other senses in the mouth which
play an important part, such as _pressure_ and the _sense of heat and
cold_, and it is often hard to distinguish them from the pure sensation
of taste, which indeed is always accompanied by them.

=Salivary Glands.=--On either side of the mouth are three racemose
glands for the secretion of the _saliva_, which serves to soften and
lubricate the food and partially to digest starches by means of its
ferment, _ptyalin_. The _parotid gland_ is the largest and is below and
in front of the ear, opening by _Stensen’s duct_. The _submaxillary
gland_ is below the jaw toward the back on either side and its duct
is _Wharton’s duct_. The _sublingual gland_ lies beneath the mucous
membrane of the floor of the mouth and opens by eight to twenty tiny
ducts beside the frenum, the _ducts of Rivinus_. The activity of the
glands depends upon the blood supply; the more blood the greater their
activity.

[Illustration: FIG. 20.--Dissection of the side of the face, showing
the salivary glands: _a_, Sublingual gland; _b_, submaxillary gland,
with its duct opening on the floor of the mouth beneath the tongue at
_d_; _c_, parotid gland and its duct, which opens on the inner side of
the cheek. (After Yeo.)]

=The Tonsils.=--The tonsils vary in size and in _tonsillitis_ swell and
may even meet in the median line. They are frequently removed. When
they are enlarged one often gets a _third tonsil_ or _adenoids_, a
lymphoid growth at the back of the pharynx which causes mouth-breathing
by day and snoring by night. A child with adenoids is starved for air
and what air is breathed in is not warmed. The growth should be removed.

A short frenum produces _tongue-tie_, which may be remedied by
snipping. Cancer of the tongue is fairly common and necessitates
a radical operation. In mumps the parotid glands are inflamed and
enlarged.

=The Ear.=--The special organ of hearing is the ear, to which there are
three parts, the external, the middle, and the internal ear.

The _external ear_ consists of the _pinna_ or expanded cartilaginous
portion, for the concentration and direction of sound waves, and the
_external auditory canal_, partly cartilage, partly bone, which is
directed forward, inward, and downward and conveys sound to the middle
ear.

[Illustration: FIG. 21.--The small bones of the ear; external view
(enlarged). (After Gray.)]

The _middle ear_ or _tympanum_ is an irregular cavity in the petrous
portion of the temporal bone. Its outer wall is formed by the _membrana
tympani_ or _drum_, an oval translucent membrane placed obliquely at
the bottom of the external auditory canal. The middle ear communicates
with the inner ear through the _fenestra ovalis_ or oval window and
contains the _ossicles_, the _malleus_ or hammer, the _incus_ or anvil,
and the _stapes_ or stirrup, which are arranged in a movable chain from
the drum to the oval window. The _malleus_, which is connected with
the membrana tympani, articulates by its head with the body of the
incus, while the stapes articulates with the _incus_ by its head and is
connected by its base with the margin of the oval window. Connection
is made between the middle ear and the pharynx and the pressure of the
air upon the drum made equal on either side by means of the _Eustachian
tubes_. These tubes are about an inch and a half long, have cilia, and
convey wax and other matter from the ear to the pharynx. Occasionally
in a cold or for some other reason they become stopped up and trouble
results in the middle ear. Some of the _mastoid cells_ also connect
with the middle ear and may become infected, causing mastoid disease.

[Illustration: FIG. 22.--Interior view of left bony labyrinth after
removal of the superior and external walls: 1, 2, 3, the superior,
posterior, and external or horizontal semicircular canals; 4, fovea
hemi-elliptica; 5, fovea hemispherica; 6, common opening of the
superior and posterior semicircular canals; 7, opening of the aqueduct
of the vestibule; 8, opening of the aqueduct of the cochlea; 9, the
scala vestibuli; 10, scala tympani; the lamina spiralis separating 9
and 10. (From Quain, after Sömmerring.)]

The _internal ear_ consists of various chambers hollowed out in
the petrous portion of the temporal bone. There is an _osseous
labyrinth_, consisting of a central cavity known as the _vestibule_,
three semicircular canals, and the _cochlea_, and within the osseous
labyrinth, surrounded by _perilymph_, is the _membranous labyrinth_,
of like form, filled with the _endolymph_. Communication exists
externally with the middle ear by the _round_ and _oval windows_ and
internally with the _internal auditory canal_, through which passes
the eighth cranial or auditory nerve, the special nerve of hearing,
which is distributed to the inner ear only. When the auditory nerve
enters the ear through this internal auditory meatus it divides into
two branches, of which one goes to the vestibule and the other to the
_organ of Corti_, a group of specially modified epithelial cells in
the cochlea of the membranous labyrinth, which is very important in
transmitting the impulses to the brain. The nerve also breaks up into
very small branches and is distributed practically throughout the wall
of the labyrinth.

The _sensation of hearing_ is the result of impulses transmitted to the
auditory nerve and so conveyed to the auditory center in the brain.
It is caused by sound waves which travel through the air from their
point of origin and enter the external ear. This collects and selects
the waves of sound and helps one to a certain extent to determine the
direction from which the sound comes. As they pass through the external
meatus the sound waves are collected into a comparatively small area
for transmission to the middle ear, where, by means of the drum, they
set in vibration the chain of ossicles. Through these the vibrations
are in turn transmitted to the oval window, being intensified in the
process. Here again they are taken up by the perilymph, from which they
pass through the wall of the membranous labyrinth to the endolymph,
affecting the epithelial lining of the labyrinth in such a way that the
impulses are transmitted to the auditory nerve, more particularly in
the vestibule, from which the vibrations enter the cochlea. They also
affect the cells of the organ of Corti in like manner as they pass from
the perilymph to the endolymph. The membrane that covers the fenestra
rotunda or round window relaxes and expands as the vibrations strike
it, thus serving to eliminate the shock of impact.

_Musical sounds_ are caused by rhythmical or regularly repeated
vibrations, while irregular vibrations give rise to noises. In
musical sounds loudness is determined by the height or amplitude of
the vibrations, pitch by the length of the wave, and quality by the
number of so called partial tones. A sensation of sound cannot be
produced by less than 30 vibrations a second and the ordinary person
cannot hear more than 16,000 vibrations a second. Different sounds
can be distinguished when they follow each other as closely as by one
one-hundredth of a second.

All sound does not come through the canal of the ear. The bones of the
head vibrate and carry sound. So there are instruments for the deaf
which are put in the ear and others which are placed between the teeth.

The _semicircular canals_ are not essential to hearing but have
something to do with a person’s power of maintaining his equilibrium.
Injury to them may cause dizziness and loss of equilibrium.

=The Eye.=--One more feature, perhaps the most expressive, remains to
be described, the eye. The senses are all modifications of the original
cutaneous sensibility and the nerve of sight is no more sensitive to
light than any other nerve. It therefore needs an end organ that is
sensitive to the motions of the ether in order to give impressions of
light. This organ is provided in the eye, which is not only itself
capable of being moved in every direction, but is placed in the most
movable part of the body, the head, which can be turned in almost a
complete circle. The _eyeball_ is spherical and lies in the cavity of
the orbit upon a cushion of fat, where it has a large range of sight
but is securely protected from injury by its bony surroundings. The
sunken eyes following protracted illness are due to the using by the
system of the fat on which the eyeball ordinarily rests.

Each _orbital cavity_ is formed by the juncture of some seven bones and
communicates with the cavity of the brain through the _optic foramen_
and through the sphenoidal fissure. Above the orbits are arched
eminences of skin, the _eye-brows_, from which several rows of short
hairs grow longitudinally and which serve to protect the eyes and to
limit the amount of light to a certain extent, as in frowning.

Still further protection is afforded by the _eyelids_, longitudinal
folds of skin, the one above, the other below, which close like
curtains over the eye. Beneath the external layer of skin in the lids
is fatty tissue and then the orbicularis palpebrarum muscle by means
of which they are closed. They are kept in shape by the tarsal plates
or cartilages, in whose ocular surface are embedded the _Meibomian
glands_, whose secretion prevents the free edges of the lids from
sticking together. Along these edges grows a double or triple row
of stiff hairs, the _eye-lashes_, which curve outward so as not to
interfere with each other and also to prevent the entrance into the eye
of foreign bodies. Lining the inner surface of the lids and reflected
thence over the anterior surface of the sclerotic coat of the eye is
a mucous membrane, the _conjunctiva_, which is thick, opaque, and
vascular on the lids but thin and transparent on the eyeball. The
angles between the lids are known as the _internal_ and the _external
canthus_.

[Illustration: FIG. 23.--The external ocular muscles. (Pyle.)]

_Muscles_ and _Nerves_.--The eyeball is held in position by the ocular
muscles, the conjunctiva, and the lids, while surrounding it, yet
allowing free movement, is a thin membranous sac, the _tunica vaginalis
oculi_. The superior and inferior recti muscles at the upper and lower
edges of the ball turn the eye up and down; the internal and external
recti at the inner and outer edges turn the eye inward and outward; and
the superior and inferior oblique rotate the eye. The nerves supplying
these muscles are the third or motor oculi, the fourth and the sixth.

The _lachrymal gland_, which is about the size and shape of an almond,
is situated at the upper and outer part of the orbit. It secretes a
fluid which keeps the anterior surface of the eye bathed in moisture
and is ordinarily drained away through the lachrymal sac in the inner
canthus, whence it passes by the lachrymal ducts into the nose. When
the amount secreted is excessive, it overflows the lower lid as _tears_.

[Illustration: FIG. 24.--Diagram of the lacrimal apparatus. (Pyle.)]

_Coats of Eye._--The membranes or coats of the eye are three in number:
an outer or sclerotic, a middle or vascular, and an inner or sensitive.

The _sclerotic coat_ is a rather thick, fibrous, protective membrane.
Where it passes in front of the iris, however, it is thinner and
transparent and is known as the _cornea_. The cornea projects somewhat
and, as it were, resembles a segment of a smaller sphere set into the
rest of the sclerotic.

The middle or vascular coat, known as the _choroid_, carries
blood-vessels for the retina or sensitive coat in its inner layer
and has an outer layer of pigment cells that excludes light and
darkens the inner chamber of the eye. The folds of the choroid at its
anterior margin contain the ciliary muscles and are known as the
_ciliary processes_, while the name _iris_ is given to the little
round pigmented, perforated, curtain-like muscle just in front of the
crystalline lens. The posterior surface of the iris is covered with a
thick layer of pigment cells to prevent the entrance of light except
through the central opening or _pupil_, and its anterior surface also
has pigment cells that give it its color, though the difference in the
color of people’s eyes is due rather to the amount of pigment present
than to its color, a small amount of pigment being present in blue eyes
and a large amount in brown and black eyes. Variations in the size
of the pupil are brought about by contractions of the circular and
radiating fibers of the iris, contraction of the circular fibers making
it smaller and those of the radiating larger. The pupil is constricted
for near objects and during sleep, and is dilated for distant objects.
In a dull light also it dilates to let in more light, and in a bright
light it contracts. The appearance of the pupil is often important as a
means of diagnosis and in etherization.

[Illustration: FIG. 25.--Vertical section through the eyeball and
eyelids. (Pyle.)]

Lastly there is the innermost _sensitive coat_ or _retina_, which has
eight layers, the outer one containing some pigment cells and the
next the rods and cones, in which the power of perception is supposed
to lie, branches of the optic nerve being distributed over it in all
directions. In fact, the retina is formed by a membranous expansion of
the optic or second cranial nerve, the special nerve of sight, which
passes into the orbit through the optic foramen at the back and enters
the eyeball close to the _macula lutea_ or _yellow spot_. The exact
spot where the optic nerve enters the retina is not sensitive and is
known as the _blind spot_. In the center of the macula lutea, however,
which is in the middle of the retina posteriorly, is a tiny pit, the
_fovea centralis_, in which all the layers of the retina except the
rods and cones are absent, and at this point vision is most perfect.
It is, therefore, always turned toward the object looked at, and when
one wishes to see an object distinctly, he must keep moving his eyes
over it that the rays from each part may fall in turn upon the fovea
centralis.

Directly behind the pupil is the _crystalline lens_, a rather firm
gelatinous body enclosed in a capsule, which is transparent in life
but opaque in death. The lens is doubly convex and is held in place
by the suspensory ligaments, which arise from the ciliary processes.
In front of it is the anterior chamber of the eye, filled with a thin
watery fluid called the _aqueous humor_, while the larger space back of
it, occupying about four-fifths of the entire globe, is filled with a
jelly-like substance known as the _vitreous humor_.

The chief artery of the eye is the _ophthalmic_.

_Light Rays._--The eye is practically a camera and its principal
function is to reflect images. Although there are several refracting
surfaces and media, for practical purposes the cornea alone need be
considered. Except for those rays which enter the eye perpendicularly
to the cornea, whose line of entrance is called the _optic axis_, all
rays are refracted when they enter the eye and the point at which they
meet and cross each other behind the cornea is called the _principal
focus of the eye_. To focus properly, all the rays from any one point
on an object must meet again in a common point upon the retina, their
_conjugate focus_. In the normal eye all the rays from an object are
focused on the retina and form upon it an image of the object which, as
in the camera, is inverted, because of the crossing of the rays behind
the cornea. Once focused on the retina the light traverses the various
layers to the layer of rods and cones, where chemical action takes
place and affects the little filaments of the optic nerve, by which the
message is carried to the brain.

[Illustration: FIG. 26.--Diagram showing the difference between (_A_)
emmetropic, (_B_) myopic and (_C_) hypermetropic eyes. (American
Text-book of Physiology.)]

When the eye is at rest the pupil and lens are in their normal
condition and at such times the eye sees only distant objects. The
ability of the eye to focus upon objects at different distances is
called _accommodation_ and to accomplish it three things are necessary:
1. change in the shape of the lens; 2. convergence of the axes of the
eyes, and 3. narrowing of the pupils.

When the eye is directed toward distant objects, the muscle fibers
in the ciliary processes relax, causing tightening of the suspensory
ligaments and consequent flattening of the surface of the lens.
Otherwise an image would be formed in front of the retina; for the
greater the convexity of the lens, the greater the angle of refraction.
Such accommodation is passive and so not fatiguing. To look at nearby
objects, on the contrary, the ciliary muscles contract, drawing the
choroid forward and allowing the suspensory ligaments to relax, so that
the lens bulges in front. This is an exertion.

In order to accommodate properly, moreover, both eyes must work
together and the axes of both eyes must be directed toward the object.
Therefore, in looking at nearby objects the axes of the eyes converge,
drawn by the internal recti muscles. In _strabismus_ or _cross eye_,
where the axes of both eyes cannot be directed toward the object at the
same time, the rays fall upon one part of one eye and upon a different
part of the other eye and two separate images are seen.

Finally there is concentric narrowing of the pupil by contraction of
the circular fibers of the iris, by which means various side rays that
would come to a focus outside the retina are excluded.

All the muscles of accommodation, the ciliary muscles, the internal
recti, and the sphincter pupillæ, are under the control of the third
nerve.

Connected with this power of accommodation and dependent on it are the
two conditions of _near-sightedness_ or _myopia_ and _far-sightedness_
or _hypermetropia_.

The normal eye is emmetropic and is almost perfectly spherical, but
in the near-sighted or myopic eye the ball, instead of being round,
is flattened from above down and so bulges in front. Consequently,
owing to the greater distance from the lens to the retina, images are
formed in front of the retina. Only nearby objects can be seen clearly,
because the farther the object from the eye the farther in front of
the retina the image is formed. Concave glasses are worn to enable
near-sighted people to see at a distance. Hypermetropic or far-sighted
eyes are flattened from before backward and can see only objects at a
distance clearly, as those nearby form images behind the retina. For
such eyes convex glasses are worn.

As the ordinary person approaches middle life, he becomes able to see
better at a distance than near to. This _presbyopia_, as it is called,
which is practically far-sightedness, is due to a partial loss of the
power of accommodation in the lens, the result of a general loss of
elasticity in the parts.

Another very common defect is _astigmatism_, a failure of the rays to
focus upon a point, owing generally to a flattening in the surface of
the cornea.

_Color perception_ is also an important function of the eye. The waves
of hyperluminous ether when of a certain rate of vibration give the
sensation of heat and when their vibrations are more rapid they give
the sensation of light. Each of the primary colors of the spectrum
gives off a pretty definite number of light rays which travel through
the air and enter the eye, the number of rays determining the color
thrown upon the retina and the velocity determining the intensity of
the color. Occasionally when light is passing through into the eye it
is broken up as in a prism and the person gets a sensation as of all
sorts of colors, _chromatic aberration_. Total or partial absence of
sensitiveness to color is called _color blindness_. It is commonest
in the form of inability to distinguish between red and green and is
probably due to a defect in the retina.

Sometimes a hair follicle on the lid becomes infected and a _sty_
is formed. _Pink eye_ is conjunctivitis or inflammation of the
conjunctiva. A Meibomian duct may become stopped and cause bulging, or
there may be a sagging down or _ptosis of the upper lid_ in certain
diseases, as meningitis, apoplexy, and more especially syphilis.
_Rodent ulcer_ often begins by the eye or on the cheek.

CHAPTER V.

THE NERVOUS SYSTEM.

The nervous system, which regulates all the vital processes of the
body, physical and chemical, and which is situated partly in the head
and partly in the trunk, may well form the connecting link between the
description of the head and that of the trunk. It has two divisions,
the cerebro-spinal system and the sympathetic system. The former
consists of the cerebrum or brain proper, the cerebellum or little
brain, the pons Varolii, the medulla oblongata, the spinal cord, and
the cranial and spinal nerves; the latter of a series of ganglia or
aggregations of nerve centers. The brain, which includes the cerebrum,
cerebellum, pons, and medulla, occupies the cranium and the spinal cord
is contained within the bony framework of the spinal column. In the
male the brain weighs about 49 ounces and in the female 44, while in an
idiot it seldom weighs more than 23 ounces.

The =cerebrum= or brain proper has two parts or hemispheres, roughly
oval in shape, each of which has five lobes separated by fissures, the
frontal, parietal, occipital, and temporo-sphenoidal lobes, and the
central lobe or _island of Reil_ at the base of the brain. The chief
fissures are the _longitudinal fissure_, the _fissure of Sylvius_
at the base of the brain, and the _fissure of Rolando_ between the
frontal and parietal lobes. There are also five serous cavities
called _ventricles_, the two lateral and the third, fourth, and fifth
ventricles, of which the first two, one in either hemisphere, are the
most important. Around these cavities is the _brain substance_, which
is made up of two tissues, the white and the gray, the latter forming
the outer part of the brain to the depth of perhaps half an inch, and
the white matter forming the rest. The outer or gray part is called
the _cortex_ and is largely made up of nerve cells. It might be called
the active part of the brain. The white part consists largely of nerve
fibers which are given off from the nerve cells and are carried down
into the spinal cord.

The surface of the brain is convoluted, the ridges being separated by
deep furrows or sulci, by which means a great extent of gray matter
is secured. The furrows contain fluid from the subarachnoid spaces
and vary in number and depth according to intelligence. While the
convolutions are not uniform in all brains, the principal ones are
constant.

Both the brain and the spinal cord are covered by three membranes, the
dura mater, the arachnoid, and the pia mater. The _dura mater_ is dense
and fibrous and lines the interior of the skull, being firmly adherent
to it at many points. In fact, it constitutes the internal periosteum
of the cranial bones. The _arachnoid_ is a delicate serous membrane,
with two layers, lubricated to prevent friction, which divides the
space between the dura mater and the pia mater, bridging over the
convolutions and enclosing the subdural and subarachnoid spaces which
are connected with lymphatics and contain a serous secretion, the
_cerebro-spinal fluid_. This fluid forms an elastic water cushion, on
which the brain rests, and prevents concussion. The _pia mater_ is
vascular, containing blood-vessels, lymphatics, and nerves, and is
closely attached to the surface of the brain, dipping down into all the
sulci.

At the base or under surface of the brain are some very important
structures. The _olfactory bulbs_ lie beneath the frontal lobe and
projecting back is the _olfactory tract_, through which the olfactory
nerves come from the brain. Back of the olfactory tract is the _optic
commissure_ where the optic nerves coming from the brain cross each
other. And back of the commissure again is the _optic tract_, where
the optic nerves emerge from the brain. At the base of the brain are
also the exits of the twelve cranial nerves.

[Illustration: FIG. 27.--Base of brain. (Leidy.) 1, 2, 3, cerebrum;
4 and 5, longitudinal fissure; 6, fissure of Sylvius; 7, anterior
perforated spaces; 8, infundibulum; 9, corpora albicantia; 10,
posterior perforated space; 11, crura cerebri; 12, pons Varolii; 13,
junction of spinal cord and medulla oblongata; 14, anterior pyramid;
14ˣ, decussation of anterior pyramid; 15, olivary body; 16, restiform
body; 17, cerebellum; 19, crura cerebelli; 21, olfactory sulcus; 22,
olfactory tract; 23, olfactory bulbs; 24, optic commissure; 25, motor
oculi nerve; 26, patheticus nerve; 27, trigeminus nerve; 28, abducens
nerve; 29, facial nerve; 30, auditory nerve; 31, glosso-pharyngeal
nerve; 32, pneumogastric nerve; 33, spinal accessory nerve; 34,
hypoglossal nerve.]

Upon entering the brain the _arteries_ run a tortuous course, the
tortuosity breaking the force of the blood stream in the small vessels
where congestion would be with difficulty relieved. The basilar artery,
which is formed by the juncture of the two vertebrals, divides into
the two posterior cerebrals, each of which joins one of the anterior
cerebrals by a posterior communicating artery. The two anterior
cerebrals also are joined by an anterior communicating artery, thus
completing the circle. The circle thus formed at the base of the brain
is called the _circle of Willis_ and provides for a good supply of
blood in event of an accident to any vessel. The blood is returned to
the general circulation through the cerebral veins and sinuses formed
by the separation of the dura mater into two layers.

The =cerebellum= is about one-seventh the size of the cerebrum and
weighs about 5 ounces. It lies in the lower occipital fossæ of the
skull and is oblong in shape and divided into two lateral hemispheres
by a transverse fissure. It is made up of both white and gray matter,
of which the former predominates, the gray being external as in the
cerebrum. The cells are about the same as in the cortex and its surface
is traversed by queer furrows. Of its function little is known but it
probably plays a most important part in the coördination of the nervous
and muscular acts by which the movements of the body are carried on.

At the back of the cerebrum and below the cerebellum is the =pons
Varolii=, which forms a connecting link with the medulla oblongata or
bulging part of the cord. It is made up essentially of white matter or
nerve fibers, though there is a small amount of gray matter in which
are found the nuclei of some of the cranial nerves.

In the =medulla oblongata=, which is about 1 inch long and extends from
the pons Varolii to the upper border of the atlas or first cervical
vertebra, the gray matter is not necessarily external to the white but
is found in patches in the white. The gray matter here corresponds more
or less to that of the spinal cord and the white matter is continuous
with that of the cord. From the medulla arise the fifth to twelfth
cranial nerves and the vasomotor nerves. The cardiac nerve has its
center here and here too are the centers of respiration, phonation,
deglutition, mastication, and expression. In the medulla the nerves
that arise in the cerebrum cross over from one side of the body to
the other on the crossed pyramidal tracts. The importance of this
crossing of the nerve fibers is seen in apoplexy, when a blood-vessel
is ruptured in the brain and hemorrhage causes pressure, generally on
the motor tract. Paralysis of the nerves and of the muscles to which
they go results. The paralysis is generally of one side of the body,
the opposite side from that on which the injury occurred. The seat
of injury in the brain or cord can frequently be determined by the
situation and extent of the paralysis.

=Spinal Cord.=--Extending down from the medulla through the spinal
column is the cord. Its length from the foramen magnum, where it
begins, down through the vertebræ to the lower border of the first
lumbar vertebra, where it ends in a very fine thread-like process with
no special function, called the _filum terminale_, is 17 to 18 inches.
Just before it ends a number of nerves are given off in a tail-like
expansion known as the _cauda equina_ or horse’s tail. It is not
uniform throughout its length but presents two enlargements, a cervical
enlargement in the lower cervical region, and a lumbar enlargement in
the lower dorsal region, where the nerves are given off to the arms and
legs respectively. The membranes are the same as those of the brain
and are continuous with them, but here the dura mater is not attached
to the bony walls enclosing it. For the cord does not fit closely
into the canal but is as it were suspended in it. The _subarachnoid
space_ communicates with the ventricles of the brain by the _foramen of
Majendie_ and is filled with _cerebro-spinal fluid_ for the protection
of the cord. In cerebro-spinal meningitis or spotted fever this fluid
is infected and for diagnosis lumbar puncture is performed.

[Illustration: FIG. 28.--Different views of a portion of the spinal
cord from the cervical region, with the roots of the nerves. In _A_ the
anterior surface of the specimen is shown, the anterior nerve root of
its right side being divided; in _B_ a view of the right side is given;
in _C_ the upper surface is shown; in _D_ the nerve roots and ganglion
are shown from below: 1, the anterior median fissure; 2, posterior
median fissure; 3, anterior lateral depression, over which the anterior
nerve roots are seen to spread; 4, posterior lateral groove, into
which the posterior roots are seen to sink; 5, anterior roots passing
the ganglion; 5´, in _A_, the anterior root divided; 6, the posterior
roots, the fibers of which pass into the ganglion, 6; 7, the united or
compound nerve; 7´, the posterior primary branch seen in _A_ and _D_
to be derived in part from the anterior and in part from the posterior
root. (Allen Thomson.)]

If a cross-section of the cord is made, it is found to have a pretty
definite structure. It is roughly circular and is divided by certain
fissures, of which the most important are the anterior and posterior
median, the latter being rather a dividing line or septum. By them
it is divided into halves connected by a small band in the middle
called the _commissure_. The white matter is exterior to the gray
and is divided by it into four columns, which again are divided into
tracts according to certain groups of nerves that travel through
them. The most important tract is the direct pyramidal tract in the
anterior column. The gray matter is arranged in the form of a letter H
practically, consisting of two lateral halves, more or less crescentic
in outline, connected by a narrow band, the _gray commissure_. Each
half is divided into two _horns_, the anterior, toward the front of the
cord, and the posterior, toward the back, the former being generally
much thicker and heavier than the latter. The structure of the gray
and of the white matter is essentially the same as in the brain,
but the proportion varies in different parts of the cord, the white
predominating in the cervical region and the gray being much better
developed in the lumbar region, where the nerve cells for control of
the lower extremities occur. The gray is least well developed in the
dorsal region. Through the center of the cord runs a small hole or
canal filled with cerebro-spinal fluid, the _central canal of the cord_.

[Illustration: FIG. 29.--Functional areas of the cerebral cortex, left
hemisphere. (A. A. Stevens.)]

The brain is the seat of intelligence and will, the center of all
voluntary action. Molecular change in some part of the cerebral
substance is the indispensable accompaniment of every phenomenon of
consciousness. Indeed, the brain is never in a state of complete
repose, there being dreams even during sleep. The brain is not
sensitive to injury in the sense of pain. It can be lacerated without
much pain.

Various centers exist in the brain, of which the most important perhaps
is the _motor center_. The _visual center_ is in the occipital lobe,
the _auditory center_ in the temporal lobe, the _speech center_ in the
third left frontal convolution. Thus the impulses of the senses have
been located, though the function of many parts, the so called _silent
areas_, are still in obscurity.

The _motor center_, that is, the center for motion of the skeletal
muscles, is situated about the fissure of Rolando and is divided into
three parts, one for the legs, one for the face, and one for the arms,
the one for the legs being uppermost and the others below in the order
mentioned. Fibers from these cells extend down through the brain and
cord to the muscles, the fibers being collected into well-recognized
bundles and the whole known as the _motor tract_. There may be one long
fiber from a cell in the brain down through most of the cord or there
may be a succession of shorter fibers that are not actually connected
but are in close contact with each other. In the upper pons the fibers
for the face cross to the opposite side, while the rest keep on down
through the medulla, and as they emerge from the medulla they too cross
to the other side and keep on down in the crossed pyramidal tract.
A few fibers do not cross but come down the direct pyramidal tract,
which, however, disappears part way down. The _crossed pyramidal tract_
is the true motor tract and in it the fibers are continually sending
branches to the cells in the gray matter, where they connect with the
anterior horn.

The anatomy of the _sensory tract_ is not so well understood. By it
impulses are sent to the brain by the peripheral organs, practically
the surface of the body. The sensory fibers connect with the sensory
cells in the posterior horn, from which fibers are sent to the brain,
practically the reverse of motor action. There are three chief sensory
tracts, which are supposed to transmit different sensations, one pain,
one muscular sensations, and the third sensations of touch. All these
tracts, of which the chief is the _direct cerebellar tract_, in passing
up the cord pass to the opposite side at different levels and then go
on to the cortex of the brain.

The action of the nerves is similar to reflex action, only that an
effort of will is needed to send an impulse from the brain. It is by
the help of the brain along this line that an infinity of artificial
reflexes or habits is acquired, for which volition is needed in the
beginning but which are later done unconsciously. Herein lie the
possibilities of all education.

The brain and spinal cord work together, the cord acting as a medium
between the brain, in which all the higher psychical processes, such as
will, thought, etc., originate, and the muscular apparatus. The cord,
however, has some action entirely independent of the brain, as is seen
in _reflex action_. This action is entirely involuntary, so that the
cord is sometimes spoken of as the seat of involuntary action, commonly
called reflex action. All unconscious acts are reflex acts, as when the
hand is drawn away from a hot iron. If an impulse is sent along one
of the sensory fibers, it enters the cord through the posterior horn,
where its nerve cell is found. Then, through some connection between
the nerve cell of the sensory fiber and that of the motor fiber the
impulse is transmitted to the motor cell and another impulse is sent
out of the cord along the motor fiber of the nerve to the muscle.
One of the commonest reflexes is the _knee-jerk_. Reflex action is
important because the reflexes are interfered with, delayed, destroyed,
or increased in different diseases. The time normally required for a
reflex act is very brief, that for the knee-jerk being about three
one-hundredths of a second.

The nerves of the head, known as the _cranial nerves_, arise from the
brain, while the rest of the body is supplied by the spinal nerves,
which come off at intervals from the spinal cord. The cranial nerves
consist of twelve pairs: (1) The olfactory or nerve of smell, (2) the
optic or nerve of sight, (3) the motor oculi, (4) the patheticus, which
controls the eye, (5) the trigeminus or trifacial, a nerve of general
sensation, motion, and taste, (6) the abducens, a motor nerve, (7) the
facial nerve of the face, ear, palate, and tongue, (8) the auditory or
nerve of hearing, (9) the glosso-pharyngeal, nerve of sensation and
taste, (10) the pneumogastric or vagus, which is both motor and sensory
and governs respiration, the heart, and the stomach, (11) the spinal
accessory, to the muscles of the soft palate, and (12) the hypoglossal,
the motor nerve to the tongue.

The _spinal nerves_ also are arranged in pairs: Eight cervical pairs,
twelve dorsal or thoracic, five lumbar, five sacral, and one coccygeal,
these titles denoting their point of origin near the vertebra of the
same name. Each of these nerves arises by two roots, an anterior motor
root from the anterior horn of gray matter and a posterior sensory root
from the posterior horn, the latter having a ganglion upon it. After
emerging from the cord the two roots unite to form the nerve, that the
nerve may contain both motor and sensory fibers. The motor fibers are
called efferent because they carry impulses _from_ the cord, while the
sensory are called afferent because they carry impulses back _to_ the
cord. After leaving the cord the nerves unite to form plexuses, which
again divide into various nerve trunks and are distributed to the
muscles.

The first _cervical nerves_ pass out of the spinal column above the
first cervical vertebra and the other cervical nerves below that
and the succeeding vertebræ, while the other spinal nerves emerge
each below the corresponding vertebra, as the first dorsal below
the first dorsal vertebra, etc. After emerging they break up into a
large anterior division and a small posterior division, the posterior
branches supplying the spine and the dorsal muscles and skin, the
anterior the rest of the trunk and the limbs. The _cervical plexus_ is
formed by the anterior divisions of the first four cervical nerves, the
_brachial plexus_ by the last four cervical and the first dorsal or
thoracic nerves, the _lumbar plexus_ by the four upper lumbar, and the
_sacral plexus_ by the last lumbar and the four upper sacral nerves.

The only important branch of any of the four upper cervical nerves,
which in general supply the neck and shoulders, is the _phrenic_, which
is distributed to the pericardium, the pleuræ, and the under surface of
the diaphragm.

The _brachial plexus_, as its name implies, supplies the arms and has
a number of important branches, as the circumflex to the shoulder, the
musculo-cutaneous to the upper arm, the elbow-joint, and the outer
surface of the forearm, the internal cutaneous to the inner side of
the arm, the median to the pronators and flexors and the fingers on
the radial side, and the ulnar to the elbow and wrist-joint. The
musculo-spiral runs down the spiral groove to the external condyle of
the humerus or upper arm bone, where it divides into the radial and the
posterior interosseous, the former going to the thumb and two adjacent
fingers and the latter to the wrist-joint and the muscles on the back
of the forearm. Sometimes, in fracture of the humerus the callus thrown
out pinches the musculo-spiral and causes pain.

The dorsal or _thoracic nerves_ supply the back with their posterior
divisions and their anterior divisions are the _intercostal nerves_.

The _lumbar nerves_ supply the abdomen, pelvis, and thigh, the chief
branches being the ilio-hypogastric to the abdomen and gluteal region,
the ilio-inguinal to the inguinal region and scrotum, the external
cutaneous and genito-crural to the thigh, and the obturator to the
thigh and the hip and knee-joints. The anterior crural descends beneath
Poupart’s ligament and divides into an anterior and a posterior
division which supply the thigh muscles, its branches going to the
pelvis.

[Illustration: FIG. 30.--Diagrammatic view of the sympathetic cord
of the right side, showing its connections with the principal
cerebro-spinal nerves and the main preaortic plexuses. (Reduced from
Quain’s anatomy.)]

The _sacral plexus_ supplies the organs of the pelvis, the thigh, and
the leg. Its chief branches are the great sciatic, the largest nerve in
the body, and the small sciatic, which go to the buttocks and thigh.
The great sciatic runs down the back of the thigh and divides at the
lower third of the thigh into the internal and external popliteal
nerves, the former of which passes along the back of the thigh to the
knee, where it becomes the posterior tibial, which in turn divides
at the ankle into the internal and external plantar. The external
popliteal descends along the outer side of the popliteal space and
divides an inch below the head of the fibula into the anterior tibial,
which supplies the flexors and skin of the ankle-joint, and the
musculo-cutaneous, which sends branches to the skin of the lower leg
and the dorsum of the foot.

=The Sympathetic System.=--Joined to the cerebro-spinal system by
intervening cords is the sympathetic system. This is made up of two
series of ganglia, one on either side of the spinal column, connected
by longitudinal bands and extending from the base of the skull to the
coccyx. They do not form an independent nervous system, each ganglion,
which seems to resemble the motor cells of the spinal cord, being
connected by motor and sensory fibers with the cerebral system.

The _sympathetic nerves_ are mostly gray, non-medullated fibers and
are distributed to viscera, secreting glands, and blood-vessels, whose
movements are involuntary and feelings obtuse. They form networks upon
the heart and other viscera and send branches to the cranium to the
organs of special sense. There are three main plexuses: The _solar
plexus_ behind the stomach, which supplies the abdominal viscera; the
_hypogastric plexus_ in front of the prominence of the sacrum, whose
nerves go to the pelvic organs; and the _cardiac plexus_ behind the
aortic arch for the thoracic viscera.

Over these nerves one has no control. A blow in the region between the
costal cartilages and below the sternum is a solar plexus blow and is
very upsetting.

The sympathetic system serves to maintain vitality in all the important
portions of the system and one of its important functions is to keep up
communication between one part and another, so that when any organ is
affected the others will act accordingly and help out to the best of
their ability.

CHAPTER VI.

THE BACK.

[Illustration: FIG. 31.--The spinal column. (Church and Peterson.)]

=The Spine.=--The trunk may be roughly divided into the back, the chest
or thorax, the abdomen, and the pelvis. By the back is denoted the
spinal column with its muscles, blood-vessels, etc., and the spinal
cord already described. The spine or vertebral column, which serves the
double purpose of holding the body erect and of protecting the cord, is
usually about two feet, two inches in length. In its course there occur
several curves, which serve to give springiness and strength and, with
the intervertebral cartilages, to mitigate the force of concussion from
blows and falls. The curve is convex forward in the cervical region,
convex backward in the dorsal, forward in the lumbar, and backward
again in the sacral region. There is most freedom of motion in the
cervical region.

As is the case with the other bones, the _vertebræ_ are specially
adapted in shape and size to the needs they are called upon to fill.
Strength and flexibility, with a minimum bulk, a channel for the cord,
and passages for the numerous nerves and blood-vessels are some of the
requirements which, in combination, they meet to an astonishing degree.
They are thirty-three in all, and are divided into groups according
to the region in which they occur: seven cervical in the neck, twelve
dorsal or thoracic, five lumbar, five sacral, and four coccygeal.

Although the vertebræ of the different groups differ more or less
in size and shape in accordance with the various demands of their
positions, they all have certain general characteristics. Each has
a body, two laminæ, two pedicles, two transverse processes, and one
spinous process. The _pedicles_ extend back from the body on either
side and support two broad plates of bone, the _laminæ_, whose juncture
at the back completes the _spinal foramen_ for the passage of the cord.
At their juncture is the _spinous process_, which can be felt beneath
the skin, while the _transverse processes_ project from the juncture of
the laminæ with the pedicles. All the processes are for the attachment
of muscles that move the spine. The _body_ is formed of cancellous bone
with a compact layer outside. Transversely it is slightly oval, while
its upper and lower surfaces are flat, except in the cervical region,
where the upper surface is concave laterally and the under convex
laterally and concave from before back. Between the bodies are disks of
fibro-cartilage, which increases motion and springiness. The _spinous
process_ or _spine_ is short in the cervical region, long and directed
downward in the dorsal region, thick and projecting almost straight
out in the lumbar region. The pedicles are notched above and below so
that when articulated the notches of two vertebræ join to form the
_intervertebral foramen_ for the outward passage of nerves and the
inward passage of blood-vessels.

The distinguishing mark of the _cervical vertebræ_ is the foramen in
each transverse process, through which the vertebral arteries run to
the skull. They are also smaller than the dorsal and lumbar vertebræ.
The _dorsal vertebræ_ are distinguished by having on the transverse
processes and on the body smooth articular surfaces called facets and
demi-facets for articulation with the ribs. The _lumbar vertebræ_ are
the largest and heaviest and have the thickest spine. By the time the
sacral region is reached, however, the vertebræ have only a rudimentary
spinous process. Moreover, in adult age the sacral bones grow together
and form one triangular bone, the _sacrum_, which has a broad base
called the _promontory of the sacrum_ and a blunt apex. It is concave
in front and convex behind and has an articulating surface for joining
the pelvic bones. In the case of the _coccyx_ also the four original
bones, all rudimentary in character and supposed to be the survival of
a tail, grow together to form one bone. Together the sacrum and coccyx
form the posterior wall of the true pelvis.

[Illustration: FIG. 32.--A type of vertebra. (Leidy.) 1, Body;
2, pedicle; 3, lamina; 4, spinal foramen; 5, spinous process; 6,
transverse process; 7, articular process.]

[Illustration: FIG. 33.--The sacrum, from before. (Drawn by D. Gunn.)]

Some of the dorsal vertebræ are peculiar in the arrangement of their
facets and demi-facets, while among the _cervical vertebræ_ are several
whose peculiarities should be more carefully noted. Thus, the first
cervical vertebra or _atlas_ supports the head and has practically no
body, the place of the body being taken by a narrow anterior arch of
bone and an opening, continuous with the spinal foramen, into which the
_odontoid process of the axis_ fits, being held in place by ligaments.
At either side on top is a facet for articulation with the occipital
bone. There is almost no spine. The second vertebra or _axis_ has
surmounting the body the odontoid process, with a facet in front for
articulation with the atlas and one behind for the transverse ligament
to move over. The seventh cervical vertebra or _vertebra prominens_
has a very long spinous process--hence name--to which is attached the
_ligamentum nuchæ_. It can be felt very distinctly on the living.

Running from the skull down through the spinal column into the sacral
vertebræ and formed by the joining of the spinal foramina of the
individual vertebræ is an opening called the _spinal canal_, which
holds the cord. The cord, however, stops practically at the first
lumbar vertebra, where it splits up into the _cauda equina_, only the
_filum terminate_ extending farther down.

Occasionally the laminæ do not form completely and the membranes of the
cord may bulge out and form a tumor, or the cord itself may come out
also. This generally occurs in the lumbar region, where it is known as
_spina bifida_. If in case of fracture of a vertebra there is paralysis
of the parts below due simply to the pressure of a fragment of bone
upon the cord, it may be completely cured by removal of the fragment.
If, however, the cord suffers injury, the paralysis will remain.
_Humpback_ or _Pott’s disease_ is caused by the tubercle bacillus,
which eats away the bodies of the vertebræ so that the column caves in
and the spinous processes are thrown out in a hump or kyphos.

[Illustration: FIG. 34.--Muscles of the right side of the head and
neck: 1, Frontalis; 2, superior auricular; 3, posterior auricular; 4,
orbicularis palpebrarum; 5, pyramidalis nasi; 6, compressor naris; 7,
levator labii superioris alæque nasi; 8, levator labii superioris;
9, zygomaticus major; 10, orbicularis oris; 11, depressor labii
inferioris; 12, depressor anguli oris; 13, anterior belly of digastric;
14, mylohyoid; 15, hyoglossus; 16, stylohyoid; 17, posterior belly of
digastric; 18, the masseter; 19, sternohyoid; 20, anterior belly of
omohyoid; 21, thyrohyoid; 22, 23, lower and middle constrictors of
pharynx; 24, sternomastoid; 25, 26, splenius; 27, levator scapulæ; 28,
anterior scalenus; 29, posterior belly of omohyoid; 30, middle and
posterior scalenus; 31, trapezius. (Dorland’s Dictionary.)]

=Muscles of the Neck.=--Before speaking of the muscles of the back
a few of those of the neck had best be taken up. They are numerous
but mostly of minor importance. Largest and most important is the
_sterno-cleido-mastoid muscle_, which has its origin on the upper part
of the sternum and the inner third of the clavicle and is inserted into
the mastoid process of the temporal bone. It passes obliquely across
the side of the neck and serves to flex the head to the side and to
draw the face in the opposite direction. When both muscles contract the
head is flexed on the neck and the neck on the chest. In _wry neck_
or _torticollis_ this muscle is constantly contracted. The _platysma
myoides_ arises from the fascia over the pectoral, deltoid, and
trapezius muscles and is inserted into the lower jaw, the angle of the
mouth, and the loose tissue in the lower part of the face. It wrinkles
the skin of the neck and depresses the lower jaw. In the cow and horse
it is so highly developed that by it the skin can be contracted all
over the body to drive off flies. The _rectus capitis anticus major_
arises from the third to the sixth cervical vertebræ and is inserted
into the occipital bone, serving to flex the head. The _scalenus
muscles_ have their origin on the lower cervical vertebræ and are
inserted into the first and second ribs, thus aiding in the elevation
of the ribs as well as in lateral flexion of the neck. The head is
held upright by the _ligamentum nuchæ_, which rises from the external
occipital protuberance and is inserted into the spinous processes of
all the cervical vertebræ except the first.

=Muscles of the Back.=--The chief back muscles are the trapezius
and the latissimus dorsi, which together cover in the back pretty
thoroughly. The _trapezius_ arises from the occipital bone, the
ligamentum nuchæ, and the spinous processes of the seventh cervical
and all the dorsal vertebræ and is inserted into the outer third of
the clavicle or collar bone and the acromion process and spine of the
scapula or shoulder blade. It is thus triangular in shape and covers in
the neck and shoulders, serving to draw the head back and to the side.
It overlaps the latissimus dorsi.

The _latissimus dorsi_ has its origin by aponeurosis from the spinous
processes of the six lower dorsal and all the lumbar and sacral
vertebræ, from the crest of the ilium or hip bone, and from the three
or four lower ribs, swings across the side, dwindling in size, and is
inserted by a small tendon into the bicipital groove of the humerus or
upper arm bone, thus covering in the part of the back not covered by
the trapezius. It draws the arm down and back, raises the lower ribs,
and draws the trunk forward, as in climbing. The flat muscles of the
back and abdomen have a tendency to flatten out into aponeuroses, such
as occurs in the origin of the latissimus dorsi.

The _levator scapulæ_, from the transverse processes of the upper
cervical vertebræ to the posterior border of the scapula, serves
to raise the angle of the scapula, and the _rhomboideus major_ and
_minor_, from the ligamentum nuchæ, the seventh cervical, and the upper
dorsal vertebræ to the root of the spine of the scapula, draw the
inferior angle back and up.

[Illustration: FIG. 35.--Muscles of the trunk from behind (left side,
superficial; right side, deep): 1, Sternomastoid; 2, splenius; 3,
trapezius; 4, latissimus dorsi; 5, infraspinatus; 6, teres minor;
7, teres major; 8, deltoid; 9, external oblique of abdomen; 10,
gluteus medius; 11, gluteus maximus; 12, levator anguliscapulæ; 13,
rhomboideus minor; 14, rhomboideus major; 15, part of longissimus
dorsi; 16, tendons of insertion of iliocostalis; 17, supraspinatus; 18,
infraspinatus; 19, teres minor; 20, teres major; 21, serratus magnus;
22, upper, and 22´, lower part of serratus posticus inferior; 23,
internal oblique; 24, gluteus medius; 25, pyriformis and superior and
inferior gemelli; 26, 26´, portions of obturator internus; 27, tendon
of obturator internus; 28, quadratus femoris. (Dorland’s Dictionary.)]

The _blood supply_ in the cervical region and about the shoulders comes
from branches of the subclavian artery, such as the suprascapular and
the transversalis colli. Lower down the supply comes from the posterior
branches of the intercostals, dorsal branches of the lumbar, and
branches of the internal iliac.

The muscles of the back are supplied by the _spinal nerves_, the spinal
accessory also going to the trapezius muscle.

CHAPTER VII.

THE CHEST.

The chest or thorax occupies the upper part of the trunk in front and
is a dome-shaped cavity containing and protecting the heart and lungs.
Its walls are formed by the dorsal vertebræ at the back, the ribs at
either side, and the sternum and costal cartilages in front, all well
covered with muscles. The floor is formed by the diaphragm. Through the
upper opening of the chest pass the trachea, the esophagus, and many
important vessels and nerves.

[Illustration: FIG. 36.--Thorax (anterior view.) (Ingals.)]

The shape of the chest may vary in disease. Thus, in rickets there is
the prominent “pigeon” breast and the rosary, that is, a bead at the
juncture of each rib with the costal cartilage, while in emphysema the
chest is enlarged in all directions and barrel-shaped. In severe cases
of lateral curvature it is distorted but may be improved by exercises.

=The Sternum.=--The sternum or breast-bone is a long narrow bone and
has three parts, the _manubrium_ or handle above, the _gladiolus_ or
sword, and the _ensiform cartilage_ at the lower end. On either side
are notches for the costal cartilages; for the first seven ribs as
well as the clavicle articulate with it. Except for some muscles along
the edges it lies directly under the skin and the ridge between the
manubrium and the gladiolus can be felt in the living, a fact which
assists in determining the position of the different ribs in cases of
fracture, as the second rib articulates at this point.

[Illustration: FIG. 37.--A and B, typical ribs; C, first rib; D,
twelfth rib. 1, head; 2, neck; 3, tuberosity; 4, grooved edge; 5,
shaft; 6, oval depression for costa cartilage.]

=The Ribs.=--The ribs are twenty-four in number, twelve on each
side, of which the upper seven, which articulate with the sternum
by individual cartilages, are called _true ribs_, the other five
_false ribs_. Of the false ribs the upper three articulate indirectly
with the sternum through the seventh cartilage, with which their
cartilages unite, while the other two have their anterior extremities
free and are called _floating ribs_. All the ribs slope down toward
the front and are by nature more freely movable in women than in
men. Most of the ribs have a head divided by a little ridge into two
facets for articulation with the dorsal vertebræ, a flattened neck,
a tuberosity at the base of the neck with a facet for articulation
with the transverse process of the vertebra below, an angle, and a
shaft, which is externally convex and is grooved on its lower edge
for the intercostal vessels and nerve. The first and second, eleventh
and twelfth ribs, however, are somewhat peculiar, the first two being
shorter, flatter and rather broader than the rest and the first having
only one facet on the head, while the last two have only one facet on
the head and no neck or tuberosity.

The _costal cartilages_ serve to prolong the ribs and greatly increase
the elasticity of the chest wall. They grow longer down to the seventh
and then decrease again in length.

The ribs, except the first and second, which are protected by the
clavicle, are frequently _broken_. Such a break causes pain in
breathing and sometimes the end of a rib pierces the lung tissue
and swelling all over the body results, due to the presence of air.
_Caries_ or death of the rib is also frequent. _Fracture of the
sternum_ occurs occasionally, generally from direct force, as from a
blow with the knee in foot-ball, and there may be dislocation between
the manubrium and gladiolus.

=Muscles of the Chest.=--The spaces between the ribs, from the
tubercle of the rib behind to the cartilage in front, are filled by
the _external intercostal muscles_, which pass downward and forward
from the lower border of one rib to the upper border of the one below.
There are, therefore, eleven pairs of these muscles. There are also
eleven pairs of the _internal intercostals_, which commence at the
sternum and extend back to the angle of the rib. These extend downward
and backward. The external intercostals raise and evert the ribs in
inspiration, the internal depress and invert them in expiration.

The chief respiratory muscle, however, is the _diaphragm_, a somewhat
fan-shaped muscle that forms the floor of the chest cavity. It takes
its origin from the ensiform cartilage, the six or seven lower ribs and
their cartilages, and from the upper three or four lumbar vertebræ,
that is, from the whole of the internal circumference of the thorax,
and is inserted into the central cordiform tendon. It has several large
and several small openings for the aorta, the esophagus, the venæ cavæ,
the thoracic duct, and various nerves, and its surfaces are covered by
serous membranes, by the two pleuræ and the pericardium above and by
the peritoneum below. It partially supports the heart and lungs. Convex
toward the chest, it becomes flattened in contraction and so increases
the capacity of the chest. It aids in all expulsive acts, as sneezing,
coughing, laughing, urinating, defecating, vomiting, and childbirth.
_Hiccough_ is spasm of the diaphragm.

[Illustration: FIG. 38.--Interior view of the diaphragm. (Leidy.)
1-3, The three lobes of the central tendon, surrounded by the fleshy
fasciculi derived from the inferior margin of the thorax; 4, 5, the
crura; 6, 7, the arcuate ligaments; 8, aortic orifice; 9, esophageal
orifice; 10, quadrate foramen; 11, psoas muscle; 12, quadrate lumbar
muscle.]

The _arteries_ of the chest are the intercostal branches of the
subclavian and the thoracic aorta, the phrenic, mediastinal, and
intercostal branches of the internal mammary, and the thoracic branches
of the axillary.

The _nerves_ are the intercostals and phrenics.

=Mammary Glands.=--On the outside of the chest walls, lodged in the
fascia of the pectoral muscles, are the mammary glands, accessory
organs of the generative system. They exist in both sexes but are
only rudimentary in the male. In the female they are small before
puberty but enlarge as the generative organs become more completely
developed, forming two hemispherical eminences, one on either side,
between the third and seventh ribs. During pregnancy they increase once
more in size preparatory to the secretion of the milk, and in old age
they atrophy. From the middle projects a small pinkish-brown conical
eminence, the _nipple_, surrounded by a paler area, the _areola_. After
the second month of pregnancy both nipple and areola become darker in
color, a point of great diagnostic value in early pregnancy.

The mammary glands themselves consist of lobules of gland tissue with
a central lactiferous tubule, the lobules being gathered into lobes
with fatty tissue between. From the juncture of these tubules result
fifteen or twenty excretory ducts, the _tubuli lactiferi_, which
converge toward the areola. Beneath the nipple they dilate, forming the
_ampullæ_, and then contract again to pass out through the nipple as
straight tubes.

_Breast abscess_ occurs most commonly in nursing mothers, as where
a part is most active there is most danger of abscess. Many benign
_tumors_ of the breast, as the fibrous tumors, occur and are especially
common in young women. If a fibrous tumor is allowed to develop it may
become cancerous. _Cancer_, however, generally occurs after the age of
forty and is usually due to some irritation, as to a blow from a ball.

The _arteries_ of the breasts are the thoracic branches of the
axillary, the intercostal, and the internal mammary.

The _nerves_ are from the thoracic cutaneous.

CHAPTER VIII.

THE HEART AND CIRCULATION.

=The Heart.=--Shielded within the chest are, as has been said, the
heart and lungs. The heart lies on the left side behind the sternum
and the cartilages of the fourth to seventh ribs in a closed, conical,
membranous sac, the _pericardium_, which is attached by its base to the
central tendon of the diaphragm, and whose point extends up between
the pleuræ of the lungs. This sac has an external fibrous layer and an
internal serous layer that is reflected back over the heart itself,
forming a closed sac, within which a thin fluid is secreted that serves
to reduce friction during the movements of the heart, the two inner
surfaces sliding over each other with every beat.

[Illustration: FIG. 39.--The heart. (Stoney.)]

[Illustration: FIG. 40.--Left auricle and ventricle, opened and part of
their walls removed to show their cavities: 1, Right pulmonary vein cut
short; 1´, cavity of left auricle; 3, 3´, thick wall of left ventricle;
4, portion of same with papillary muscle attached; 5, the other
papillary muscles; 6, 6´, the segments of the mitral valve; 7, in aorta
is placed over the semilunar valves; 8, pulmonary artery; 10, aorta and
its branches. (Allen Thomson.)]

The heart itself is a hollow conical organ composed of cardiac muscle,
a combination of smooth and striated fibers found nowhere else in the
body. It lies obliquely, base up, between the lungs, suspended by the
great blood-vessels and with the apex directed downward, forward, and
to the left, the apex beat being normally felt in the fifth intercostal
space, one inch inside and two inches below the left nipple. In size
it varies in different people and is generally smaller in women than
in men. On the average it is five inches long, three and a half inches
broad, and two inches thick. A man’s heart usually weighs about eleven
ounces and that of a woman nine ounces. It never leaks except from
disease and such leakage is fatal.

_The Cavities._--The heart contains four cavities, two _auricles_ above
and two _ventricles_ below, with a longitudinal septum between the
auricle and ventricle on the right and those on the left. The posterior
surface is largely made up of the left ventricle and the anterior of
the right ventricle. The right auricle, which receives the blood from
the general circulation, has a capacity of about two fluid ounces and
is larger than the left, which receives the blood returning from the
lungs, though its walls are thinner. Of the ventricles the left is the
larger and its walls are about three times as thick as those of the
right, for it has to send the blood all over the body. All the cavities
are lined with smooth, transparent, serous membrane, the _endocardium_,
which is continuous with the intima of the great vessels.

[Illustration: FIG. 41.--Orifices of the heart, seen from above, both
the auricles and the great vessels being removed: _PA_, Pulmonary
artery and its semilunar valves; _Ao_, aorta and its valves; _RAV_,
tricuspid, and _LAV_, bicuspid valves; _mv_, segments of mitral valve;
_lv_, segment of tricuspid valve. (Huxley.)]

_The Valves._--The opening from the auricle into the ventricle on
either side is guarded on the ventral side by a valve formed of folds
of endocardium. The valve on the right side has three flaps or cusps
and is called the _tricuspid valve_, while that on the left has two
flaps, larger and thicker than those of the tricuspid, and is known as
the _bicuspid_ or _mitral valve_. The flaps of either valve are kept
from being forced into the auricle in closing by fine tendinous cords,
the _chordæ tendineæ_, which are attached to the _columnæ carneæ_,
muscular bands or columns projecting from the walls of the ventricle,
which contract and hold the chordæ tendineæ taut. The opening into the
pulmonary artery is from the posterior part of the right ventricle
and is guarded by the _semilunar_ or _pulmonary valve_, while the
aortic opening from the left ventricle is guarded by a similar valve,
the _aortic valve_, the most important valve in the body. All these
valves are planned primarily to prevent regurgitation of the blood
during contraction of the heart muscle. Pressure in the ventricle must
exceed that in the arteries before the semilunar valves will open and
the blood can be driven out, just as the auriculo-ventricular valves
remain closed until the pressure in the auricles exceeds that in the
ventricles.

The _heart beat_ is caused by the twisting of the heart upon its axis
during contraction of the muscle. Normally it beats rhythmically and
regularly, whatever a person does, at a rate of about seventy-two
contractions to the minute in the adult. To the regular _cardiac
cycle_, as it is called, there are two periods, the _systole_ and the
_diastole_, the former representing the period of contraction of the
ventricles, when the blood is sent to the lungs and over the body,
and the latter representing the period of rest following the emptying
of the ventricles, during which they are refilled. Contraction of
the heart occupies one-fifth of the time of one beat, dilatation
two-fifths, and the pause two-fifths. There are really two systoles,
one of the auricles and one of the ventricles, but they come so close
together that they are practically simultaneous so far as sound is
concerned, though they can be distinguished by sight. During systole
the tricuspid and mitral valves close sharply to prevent regurgitation
into the auricles, while the semilunar valves open to let the blood
out. The cardiac cycle is, therefore, as follows:

[Illustration: FIG. 42.--Diagram of the circulation. (After Kirke.)]

=Circulation.=--The blood, after it has given off its oxygen and
collected carbon dioxide, returns to the heart through two main
channels, the _superior_ and _inferior venæ cavæ_, the former bringing
the blood from the upper part of the body, including the head, neck,
and arms, and the latter from the lower part below the diaphragm. The
two vessels empty along with the _coronary sinus_, which is guarded
by the _coronary valve_, into the right auricle. At the same time
that they empty into this auricle the four _pulmonary veins_, the
only veins that carry arterial or oxygenated blood, are emptying the
fresh blood from the lungs into the left auricle. When both auricles
are full, they contract and send the blood into the ventricles, the
_auricular systole_. As the blood comes through into the ventricles it
probably comes around by the walls and closes the auriculo-ventricular
valves, though just how the valves close is not certain. When the two
ventricles are full they in turn contract, the _ventricular systole_,
and the blood is forced out, that in the right ventricle passing to the
lungs for its new supply of oxygen through the _pulmonary artery_, the
only artery to carry venous blood, and that from the left ventricle
entering the aorta for general distribution through the body. Following
the systole is a pause, the _diastole_, while the heart fills again.

[Illustration: FIG. 43.--The fetal circulation.]

_Circulation in Fetus._--In the fetus there is direct communication
between the two auricles through the _foramen ovale_, which normally
closes at birth, though occasionally it remains open. There is also
communication between the pulmonary artery and the arch of the aorta
through the _ductus arteriosus_. The freshly oxidized blood comes
to the fetus through the placenta, from which it is brought along
the umbilical cord in the umbilical vein to the liver and thence to
the inferior vena cava, where it mixes with the blood from the lower
extremities. By the inferior vena cava it is carried to the right
auricle, where the _Eustachian valve_--a valve between the inferior
vena cava and the auriculo-ventricular opening, larger in the fetus
than in later life where it serves no special purpose--guides it across
the auricle and through the foramen ovale to the left auricle. From
this auricle, together with a small amount of blood from the lungs,
it goes to the left ventricle and is distributed by the aorta almost
entirely to the head and upper extremities. Hence their large size and
perfect development at birth. Returned from the upper extremities by
the superior vena cava, the blood enters the right auricle again and,
passing over the Eustachian valve this time, descends to the right
ventricle, from which the greater part passes by the pulmonary artery
and the ductus arteriosus to the descending aorta, though a small
amount keeps on through the pulmonary artery to the lungs. In the aorta
it mixes with the blood from the left ventricle and part goes to supply
the lower extremities, though the greater part is carried back to the
placenta through the two umbilical arteries. The fact that the greater
part of the blood traverses the liver accounts for its large size at
birth, while the lower extremities, which receive for the most part
blood that has already circulated through the upper extremities, are of
small size and imperfectly developed.

=Arteries.=--After birth the arterial blood for the general circulation
leaves the heart by the aorta, the main distributing artery of the
body. Through this and its branches it is carried throughout the body
in what, with the return of the venous blood by the venæ cavæ and other
smaller veins, is known as the _systemic circulation_. The _aorta_
ascends from the left ventricle and arches backward to the left over
the root of the left lung to descend along the spinal column at the
left to the fourth lumbar vertebra, about opposite the umbilicus,
where, considerably diminished in size by the branches it has given
off, it divides into the two _common iliacs_. For convenience its
different parts are named, according to their position, the _ascending
aorta_, the _arch of the aorta_, and the _descending aorta_, the last
being subdivided into the _thoracic_ and the _abdominal aorta_.

[Illustration: FIG. 44.--The aortæ and their branches. (Leidy.)]

From the ascending aorta come off the _coronary arteries_ which supply
the heart muscle itself, as the coronary sinuses carry off the venous
blood from the heart. From the arch are given off the _left common
carotid_ and _left subclavian_ and the _innominate_, which divides into
the _right common carotid_ and _right subclavian_.

The _common carotids_ pass up the neck behind the sterno-cleido-mastoid
muscles in a line from the sterno-clavicular joint to a point midway
between the mastoid process and the angle of the lower jaw and divide
opposite the upper border of the thyroid cartilage into the _internal_
and _external carotids_, of which the former with its branches supplies
the anterior part of the brain, the eye and forehead, and the latter
the neck and face.

The _subclavian_ is the artery of the upper extremity but its vertebral
branch goes to the brain, where with its fellow it forms the _basilar
artery_, whose branches together with the branches of the internal
carotid form the _circle of Willis_ at the base of the brain. Other
branches of the subclavian are the _thyroid axis_, with branches to
the neck and shoulders; the _internal mammary_, with branches to the
chest walls, mediastinum, and diaphragm, such as the musculo-phrenic
and superior epigastric; and the _superior intercostal_. At the lower
border of the first rib, over which it passes, the name _axillary_ is
substituted for _subclavian_, while at the lower border of the axilla,
where it starts down the arm, it is called the _brachial artery_. At
the elbow the brachial divides into the _radial_ and _ulnar arteries_.
The _axillary artery_ sends branches to the chest and shoulder and is
more frequently injured than any other artery except the popliteal.
_Aneurism_ may occur in it and is very likely to occur in the thoracic
aorta.

From the _thoracic aorta_ branches go to various of the chest contents,
while the _abdominal aorta_ supplies the abdominal viscera. Among the
branches of the abdominal aorta are: the _celiac axis_, which has a
gastric, an hepatic, and a splenic branch; the _superior_ and _inferior
mesenteric_ to the intestines; the _renal_; the _suprarenal_; the
_spermatic_ or _ovarian_; the _inferior phrenic_; and the _lumbar_.

The _common iliacs_ divide at the upper edge of the sacrum into the
_external_ and _internal iliacs_, of which the latter with its branches
supplies the walls and viscera of the pelvis and the inner part of the
thigh. The external iliac and its branches go to the thigh, leg, and
foot.

=Veins.=--Of the veins few need be mentioned by name. The deep veins
have the same names as the arteries they accompany, though there are
two _innominate veins_ where there is only one innominate artery,
the _subclavian_ and _internal jugular_ veins on either side joining
to form an innominate vein and the two innominates in turn forming
the _superior vena cava_. Of the superficial veins the _external_
and _internal jugular_ correspond to the common carotid arteries and
return the blood from the head and face. The external jugular vein is
important because it is the largest superficial vein in the neck and
is often cut in suicide. The _median vein_ is found at the bend of
the elbow and is used in letting blood and in giving salt solution,
while the _basilic_ is on the inner side and the _median cephalic_
on the outer side of the upper arm. _Varicosity_ often occurs in the
_internal_ or _long saphenous_ and the _external_ or _short saphenous_
in the leg. The _inferior vena cava_ is formed by the juncture of the
two _common iliac veins_.

=Portal Circulation.=--The portal system of veins includes four large
trunks which collect the blood from the viscera of digestion, the
_superior_ and _inferior mesenteric veins_ from the intestines, the
_splenic vein_ from the spleen, and the _gastric_ from the stomach.
These join together to form the _portal vein_, the only vein that
breaks up into capillaries. This divides and ramifies through the
liver, whence it emerges as the _hepatic veins_. The whole is known as
the portal circulation.

=Pulmonary Circulation.=--Of the pulmonary circulation and its vessels
a few words might also be said. The _pulmonary artery_, which carries
the blood from the right ventricle to the lungs, is only about two
inches long and divides into a right and a left pulmonary artery, which
pierce the pericardium and go to their respective lungs. The right one
is the larger and longer, for it has farther to go and gives off a
branch to supply the third lobe of the right lung. The vessels finally
divide and subdivide, terminating in the _pulmonary capillaries_.
The venous capillaries then gather together to form a main vein in
each lobule, these veins uniting into two trunks for each lung, the
_pulmonary veins_, which empty into the left auricle.

=Nerves of Heart.=--The muscular fibers of the heart have the power
of rhythmical contraction. Independent nerve centers or ganglia are
also found in the muscular walls and influence the mechanism of the
heart, especially the acceleratory mechanism. Thus, in some of the
lower animals the heart can be removed from the body, and if placed in
normal salt solution will go on beating for some time. The heart is
controlled, however, by two nerves, the _vagus_ or _pneumogastric_ and
the _sympathetic_. Of these the vagus is the inhibitory mechanism. It
acts as a check and makes the heart’s action regular and rhythmic. If
it is cut, the action of the heart becomes very rapid and irregular.
The sympathetic is the acceleratory mechanism. When the vagus alone
is stimulated, it first slows, then stops the heart, for it weakens
the systole and prolongs diastole. Acceleration follows stimulation
of the sympathetic, both the rapidity and the force of the beat
being increased. When a person faints from a blow in the abdomen, it
is because the pneumogastric is affected and inhibits the action of
the heart. The work of the heart is very dependent upon its nervous
condition and functional diseases of the heart are practically wholly
due to nervous derangement.

=Heart Sounds.=--Through the stethoscope two heart sounds may be heard.
They are known as the first and second sounds. The first is a soft,
rushing sound, stronger and louder than the other, and is caused in
part by the contraction of the muscle itself when the blood is forced
out and in part by the closure of the auriculo-ventricular valves.
The second sound is shorter and sharper, a snap, and is caused by the
closure of the semilunar valves when the contraction of the ventricles
ceases and they begin to refill. In certain diseased conditions, where
the edges of the valves are roughened, they do not snap properly and
the sound varies from the normal.

=The Heart Beat.=--The rate of the heart beat is proportionate to the
size of the person and increases in rapidity as the size diminishes.
If the ear is placed over the abdomen of a pregnant woman, the heart
of the fetus can be heard beating very rapidly. In prolonged labor it
may become more rapid or very faint and warn the doctor that something
should be done. The usual rate of the pulse in the fetus is 140 to 150
times a minute, though it varies with size and sex. At birth it drops
to 140 to 130; for the first year it is 130 to 115; for the second
year 115 to 105; for the third year 105 to 95; from the seventh to the
fourteenth years 80 to 90; from the fourteenth to the twenty-first
years 75 to 80; from twenty-one to sixty 60 to 75. In old age it rises
a little and is 75 to 80. The rate is higher in the average woman
than in the average man and increases with exercise, with increase of
temperature, and in high altitudes, where the atmospheric pressure is
less.

At each beat of the heart from four to six ounces of blood are
expelled into the pulmonary artery and the aorta, and in 22 or 23
beats all the blood in the body passes through the heart. The power
exerted by the heart every minute in thus driving the blood upon its
course has been estimated as sufficient to raise its own weight,
three-quarters of a pound, the height of the Washington monument or 150
meters; for the ventricles have to force the blood into vessels already
full.

=Factors Affecting Circulation.=--There are three main factors in the
circulation: 1. the systole, which gives the blood its first impulse;
2. the peripheral resistance in the capillaries, which serves to hold
it in check, slowing the circulation and doing away with its rhythmic
character, and 3. the elasticity of the walls of the arteries.

If a ligature is tied about an artery, there is a swelling on the side
toward the heart, while in the case of a vein, the swelling is on the
side away from the heart, that is, the swelling is in either case on
the side from which the blood comes. When an artery is cut, however,
the blood comes out rhythmically in spurts, though from a cut vein it
oozes slowly and regularly. For the blood is pumped out by the heart
rhythmically and its rhythmic beating against the walls of the artery
is felt in the _pulse_, which follows slightly after the beat of the
heart itself. The pulse is due to the fact that the vessels into which
the blood is forced are already full. This causes a local dilation at
the beginning of the artery which passes with diminishing force along
its entire length, the distention being due to the fact that more force
is needed to drive the blood through the small arteries and capillaries
than to stretch the elastic walls of the aorta and the large arteries.
It is this elastic character of the arteries that makes the blood flow
constant, for otherwise the blood would come intermittently in jets, as
it is pumped from the heart. The elastic walls of the vessels, however,
offer a certain resistance to the pumping of the fluid through them and
at the same time, by relaxing between whiles, allow a certain amount of
fluid to be retained in them, so that they continue full and the flow
is more or less constant. The insufficient outlet also helps to make
the flow constant.

By the time the blood reaches the veins its rhythmic character has
been done away with, but though there are no elastic walls in the
veins, it still has force enough after the slowing in the capillaries
to return to the heart. In this it is aided to a certain extent by
the valves and by the action of the skeletal muscles as they contract
and expand, especially in the arms and legs, where the blood runs
perpendicularly and there is a high column to be supported. There are
also more veins than arteries, each large artery having two large
veins, the venæ comites, to help get the blood back to the heart, and
the veins anastomose freely. Thus, if the blood cannot get back by one
channel it does by another. In parts like the brain, where it is very
important that there should be no compression, since any disturbance
of circulation would lead to serious results, the vessels are enclosed
in thick walls, and in the liver, through which all the blood passes
and where compression is sure to cause trouble, the veins are simply
caverns carved out in the organ and have no walls. They lie open when
the organ is opened. _Varicose veins_ are the result of valves giving
way through inherited weakness or disease so that others have an unduly
large weight to support.

=The Pulse.=--The _pulse wave_ is characterized by a quick rise and
a slow fall, though this cannot ordinarily be distinguished by the
finger. In some slow fevers, however, the fall is very long and
distinct ripples can be felt. This is known as the _dicrotic pulse_.
With age the arterial walls grow stiffer and more rigid and less
adapted to their work. In certain cases of heart disease the heart does
not transmit all the beats to the pulse and to get the true rate the
heart must be listened to.

The rate at which the pulse wave travels varies with the size of the
artery and the force of the heart beat but is about 15 to 20 feet
a second. The flow is most rapid in the arteries because they are
nearest the heart, where the pressure is greatest, and slowest in the
capillaries, where the area is greatest, the sectional area of the
capillaries, known as the _peripheral area_ because it is farthest from
the heart, being larger than that of the large arteries. Thus rapidity
of flow varies with pressure and with area.

=Blood Pressure.=--Liquids, moreover, are incompressible and exert
pressure on the walls of the tubes through which they pass. The amount
of pressure depends upon the inflow and outflow, increasing directly
with the inflow and inversely with the outflow, that is, the smaller
the outlet the greater the pressure, and _vice versa_. The pressure
is also greatest nearest to the inflow and gradually decreases with
distance until at the point of outflow there is practically no
pressure. So, in the arteries the blood pressure is greatest in the
large vessels nearer the heart and gradually decreases as they branch
into smaller and smaller vessels. In passing through the capillaries,
owing to their small size and resultant increased friction, the
blood meets with more resistance, the peripheral resistance, and
this resistance usually regulates the pressure in the arteries. The
greater the peripheral resistance, as a rule, the greater the arterial
pressure. The pressure in the capillaries is very slight and in the
veins there is practically no pressure. In fact, in the large veins
near the heart the pressure is negative and the blood is almost sucked
into the heart.

Pressure, then, is greatest in the arteries and least in the veins,
while the rate of flow is fastest in the arteries--300 to 500
millimeters a second--and slowest in the capillaries--75 millimeters
a second--being a little faster again in the veins--200 millimeters a
second.

Blood pressure is gauged by opening a vessel and inserting a
_manometer_, the pressure being determined by the height to which the
mercury is raised. In man the pressure in the arteries is 120 to 160
millimeters. It is considerably heightened during inspiration by the
increased pressure of the lungs on the heart and great vessels. In
pericarditis the opposite is true.

When the blood pressure is high, the _pulse_ is small and travels fast,
because the wall of the artery is already highly stretched. Such a
pulse is hard and incompressible. A large pulse occurs where the heart
is strong and the pressure is low, owing to peripheral dilatation. A
low-pressure pulse is soft and compressible if the heart beat is weak.
A slow pulse is generally stronger than a rapid one.

The _nerve supply of the blood-vessels_ comes from the spinal cord
through the vasomotor nerves, which are connected with the sympathetic
system and are distributed to the smooth muscle fibers of the vessels.
They are of two classes, the _vasoconstrictors_, which diminish the
lumen of the vessels, and the _vasodilators_, which increase the size
of the vessels. By these nerves the general tone of the arteries is
kept up. They are distributed chiefly to vessels in the skin and
in the abdominal organs and the constrictors are probably the more
important. When the constrictors are stimulated, three phenomena occur:
1. diminished flow through the vessel, due to its diminished size; 2.
increased general arterial pressure, and 3. increased flow through
the other arteries. When the dilators are stimulated the opposite
effect is produced: 1. the flow through the vessel is increased; 2.
there is decreased arterial pressure, and 3. there is decreased flow
through the other arteries. The palor of fright is due to the action
of the vasoconstrictor nerves of the face and blushing to the action
of the vasodilators. Heat stimulates the vasodilators so that more
blood goes to the skin, perspiration begins, and the body is cooled by
evaporation. Cold stimulates the vasoconstrictors and the blood is kept
within the body, where it cannot cool. If a part has too much blood,
an impulse passes by the vasoconstrictors to lessen the supply, while
if more blood is needed a message goes to the central nervous system
and an impulse passes by the vasodilators to flush the organ. The more
active a part is in functioning the greater the number of capillaries,
except in the brain, which has only large vessels. The vessels of the
intestines contain much blood and are capable of containing all the
blood in the body.

=The Blood.=--The blood itself, which thus circulates through the body,
carrying nutrition to the tissues and removing waste, is a complex
fluid of a bright red color. Its amount has been calculated to be
about one-thirteenth of the body weight. One-fourth of it is generally
in the heart, lungs, and large arteries and veins, one-fourth in the
liver, one-fourth in the skeletal muscles, and one-fourth variously
distributed through the other organs. If there is too little blood, the
vital processes cannot go on as they should, while too great a supply
causes weakness rather than strength. So the tendency is to keep the
amount constant and any blood added is disposed of and any blood lost
is replaced. In starvation it is the last tissue to be used up, for on
it the life of the other tissues depends.

_Composition._--In composition the blood is practically the same in
all arteries and fundamentally the same everywhere, but in passing
through certain organs certain substances are added to or taken from
it, so that its character changes more or less. Thus it varies somewhat
in composition in different parts of the body, as in the liver and
kidneys. It has five main functions: 1. the conveying of fuel from the
digestive tract to the tissues, or force production; 2. the carrying of
oxygen to the tissues; 3. the carrying of tissue-building materials,
or tissue building; 4. the distribution of heat; and 5. the removal of
waste products.

The blood is slightly alkaline in reaction, of a saltish taste, and has
a specific gravity of 1055. Its temperature is about 100° Fahrenheit or
37.8° Centigrade. It is made up of two parts, the _plasma_ or fluid
portion and the _corpuscles_ or solid portion. The plasma, again, which
is transparent and almost colorless, consists of two materials, the
_blood serum_ and _fibrin_. Fibrin does not exist as such in the body
nor in freshly shed blood, but there is a substance named _fibrinogen_
which is worked on by another substance, the _fibrin ferment_, to form
fibrin. Both fibrin ferment and fibrinogen can be isolated from the
blood.

_Coagulability._--In the body the blood is perfectly fluid and under
normal conditions does not coagulate. But, though fluid when first
shed, upon standing it gradually becomes viscid, that is, in two or
three minutes, then jelly-like, in five to ten minutes, and grows
firmer and firmer until there finally appears around this jelly-like
mass or clot a yellowish fluid, the _serum_. The _clot_ is made up of
the corpuscles and fibrin. If some blood is drawn and set on ice until
the corpuscles settle, the plasma can then be drawn off, and after it
has stood a while in a warm place coagulation will take place, a mass
of fibrin forming in the middle. It takes from one to two hours for
clotting to be complete. In very slow clotting at a low temperature the
white corpuscles appear in a layer on top of the clot, the buffy coat.

Of _fibrin_ little is known, but its formation is the most important
step in clotting, as its presence is absolutely essential. If it
is removed by whipping, the blood will not clot. It is a delicate,
stringy material, elastic and contractile, and contains certain salts
of lime and magnesium, upon whose presence its power of coagulation
depends. The coagulability of blood differs in different people and is
occasionally so little as to make operation dangerous.

The most favorable temperature for clotting is that of the body,
extreme heat preventing it and cold delaying it. That the blood does
not clot in the body must be due to some relation between the blood
and the walls of the arteries and veins that prevents it, just as the
walls of the stomach are not digested by the juices secreted. Though
coagulation does not normally take place in the body, it does take
place when a blood-vessel is injured or when the blood comes in contact
with the air, a wise provision of nature, as otherwise the tendency
would be for bleeding to go on indefinitely after injury. The greater
the surface with which the blood comes in contact the more quickly it
clots. Injury to the vessel wall itself is necessary; the endothelium
must be cracked. Under extreme injury the muscular coat of the vessel
undergoes spasmodic contraction and partially closes it. Hence a wound
caused by tearing is less likely to bleed than one due to cutting.

The valves of the heart, which are covered with endothelium, are
frequently the seat of fibrin coagulation, bits of the fibrin thus
formed giving rise to conditions in various kinds of heart trouble. Or
the bits of fibrin float in the blood and perhaps lodge in the small
vessels of the brain and cause apoplexy. Pus in various parts of the
body will set up coagulation in nearby arteries. In fact, the presence
of any foreign substance in the blood causes clotting.

[Illustration: FIG. 45.--Cells of blood: _a_, Colored blood-corpuscles
seen on the flat; _b_, on edge; _c_, in rouleau; _d_, blood platelets.
(Leroy.)]

=Blood-corpuscles.=--The solid parts of the blood are the red
corpuscles, the white corpuscles, and the blood plaques or plates.
It is to the _red corpuscles_, or _erythrocytes_ which number about
5,000,000 to the cubic millimeter of blood, that the color of the
blood is due. Under the microscope they appear as small, spherical,
biconcave discs with a slightly greenish-yellow color, which have
a tendency to form in rouleaux. They are homogeneous, with no
limiting membrane, and are made up of a fine network of tissue, the
_stroma_, in which is embedded the hemoglobin or coloring matter.
This hemoglobin is a crystalline body and the most complex substance
known to chemists. The corpuscles are very flexible and can squeeze
through small apertures, as in the tiny capillaries, and regain their
shape. They are probably formed chiefly in the red bone marrow at the
ends of the bones, which under the microscope shows red corpuscles in
various stages of growth, and also in the spleen, for which no other
use is known. Their function is to carry oxygen, which forms a chemical
combination, though an extremely loose one, with the hemoglobin. As the
tissues are more greedy of oxygen than is the hemoglobin, they rob the
corpuscles of it.

[Illustration: FIG. 46.--Various forms of leucocytes: _a_, Small
lymphocyte; _b_, large lymphocyte; _c_, polymorphonuclear neutrophile;
_d_, eosinophile. (Leroy.)]

The _white corpuscles_ or _leucocytes_ are much fewer in number,
about one to from 300 to 700 of the red, the average number being
5,000 to 10,000 to the cubic millimeter. They are larger than the red
corpuscles, colorless, and spherical when at rest. Their structure is
more definite, there being a definite cell substance or protoplasm
and one or more nuclei, which vary more or less in shape and size.
The corpuscles are classed in accordance with these variations in the
nuclei. They are most numerous during digestion and are probably formed
in the lymphatic system, constantly passing from the lymphatics to the
arteries and veins. For they have the function of amœboid movement by
which they not only wander from place to place in the blood, keeping
close to the sides of the vessels, but pass through the walls of the
capillaries, probably between the cells which form their lining, into
the lymph spaces. This is known as _migration of the white corpuscles_.
In inflammation they collect in the inflamed area to assist in allaying
the inflammation by absorbing and carrying off its products. For they
carry waste products and destroy poisons, acting as scavengers and
protectors of the body. When they are unsuccessful and the inflammation
gets the better of them, they become _pus corpuscles_.

Besides the corpuscles there are seen floating in the blood small
disk-like substances with no special characteristics, the _blood
plaques_ or _plates_, whose function is unknown.

In _anemia_ the red corpuscles are diminished and the white corpuscles
and blood plaques increased in number. After excessive bleeding normal
salt solution is injected, subcutaneously or by rectum, as being nearly
equivalent to blood serum in composition, and the renewal of the
solid elements is left to time. The length of time needed for their
restoration is about a week, except in the case of the hemoglobin,
which takes longer.

CHAPTER IX.

THE LUNGS AND RESPIRATION.

Besides the heart and the great vessels the chest contains the lungs,
the chief organ of respiration, which, with the rest of the respiratory
system, will now be treated. The nose and mouth, through which the air
first enters the body, have already been spoken of. From them the air
passes through the larynx to the trachea, thence to the bronchi, and so
to the lungs, where the supply of oxygen for the tissues is taken from
the air by the hemoglobin of the blood.

=The Larynx.=--The larynx lies in front of the pharynx at the upper
and fore part of the neck, where it causes a considerable projection,
known as _Adam’s apple_. It is a triangular box, base up, flattened
at the back, in front, and at the sides, but becoming cylindrical
below. Above it opens into the bottom of the pharynx and below into the
trachea. It is lined with mucous membrane. Its opening at the base of
the tongue is closed during swallowing by a little door-like valve of
fibro-cartilage, the _epiglottis_, to prevent the entrance of food.

Nine _cartilages_ go to make up the larynx, of which the most important
are the thyroid and cricoid cartilages and the epiglottis already
mentioned. The _thyroid_ is the largest and is open behind, its two
alæ or wings meeting in an acute angle in front and forming the Adam’s
apple, always more prominent in the male than in the female. It is
attached above to the hyoid bone and has cornua or horns on either
side, top and bottom. The _cricoid_ or ring-like cartilage resembles
a seal ring with the stone placed posteriorly. It is stronger than
the thyroid and forms the lower part of the cavity of the larynx.
Inside and resting on the upper border of the cricoid are the two
smaller _arytenoid_ or pitcher-like cartilages, pyramidal in shape,
and surmounting these again the two _cornicula laryngis_. The two
_cuneiform cartilages_ are in the free borders of the folds of mucous
membrane which extend from the apex of the arytenoids to the sides of
the epiglottis. Numerous small muscles serve to bind these various
cartilages together.

At the angle of the thyroid cartilage in front are attached the
epiglottis at the top and just below that the _superior_ or _false
vocal cords_, two folds of mucous membrane enclosing the _superior
thyro-arytenoid ligaments_. Lower still are found the _inferior_ or
_true vocal cords_, which are formed by the _inferior thyro-arytenoid
ligaments_ covered with a thin, tightly fitting mucous membrane. Both
sets of vocal cords as well as the epiglottis may be seen by means
of a head and a throat mirror. Between the true vocal cords is a
narrow triangular interval called the _glottis_. It is by means of the
vibrations of these cords that sound is produced. The false vocal cords
cannot produce sound, though they can modify it indirectly. Quality of
voice, as treble, base, etc., depends upon the size of the larynx and
the length and elasticity of the vocal cords. Modulation is produced by
changing the form of the cavity of the mouth and nose. In whispering
the lips take the place of the vocal cords and produce sound by the
vibration of their muscular walls.

Instead of tracheotomy _laryngotomy_ is sometimes done in the
depression between the thyroid and the cricoid, which may be felt on
the living. _Foreign bodies_ sometimes get into the larynx and have
to be removed, or the mucous membrane may become inflamed, causing
_laryngitis_. _Syphilis_ attacks the larynx, and _tuberculosis_ and
_cancer_ of the larynx occur, these last two being generally fatal.
_Edema of the glottis_ may also occur.

[Illustration: FIG. 47.--The larynx, trachea and bronchi (After
Sobotta.)]

=The Trachea.=--The trachea is a membranous tube extending down from
the larynx for about four and a half inches to the fourth or fifth
dorsal vertebra, where it divides into the right and left bronchi. It
is formed of sixteen to twenty imperfect cartilaginous rings, open
behind, enclosed in a double elastic fibrous membrane, and is lined
with ciliated mucous membrane. The rings are for strength and in
the interval at the back where they are wanting there is one layer
of longitudinal and another of transverse unstriped muscle fibers.
The passage is kept clear by the action of the cilia, which sweep up
and out any particles of dust that become entangled in the mucus.
_Tracheotomy_ is generally done about one inch below the cricoid, just
above the sternal notch, incision being made through the cartilage.

[Illustration: FIG. 48.--The upper thorax of a child eight years old,
showing the thyroid and thymus glands. (Sobotta.)]

Extending up on either side of the upper trachea in the neck are the
two lobes of the _thyroid gland_, the isthmus, which connects the
lobes, covering the trachea below anteriorly. The function of the gland
is obscure, but it has an internal secretion of great importance in
the metabolic processes. Its removal or disease is followed by general
disturbances of mind and body. The injection of thyroid extract has
proved effective as treatment. In _goiter_ the gland becomes enlarged.
The _thymus gland_ lies below the thyroid gland at birth, in front of
and at the sides of the trachea, and runs down behind the sternum. It
is largest at the end of the second year, after which it atrophies,
being almost absent at puberty. It, too, is ductless and its function
is not well understood.

=The Bronchi.=--The two bronchi, of which the right is the larger and
shorter, resemble the trachea in structure. As they enter the root
of the lung they divide, the right into three and the left into two
branches, one for each lobe, after which they divide and subdivide,
the bronchioles becoming smaller and smaller and finally ending in the
_infundibula_, pouch-like places lined with air cells, in which cilia
keep the air in motion. As they grow smaller the bronchioles gradually
become wholly membranous.

[Illustration: FIG. 49.--Relation of lungs to other thoracic organs.
(Ingals.)]

=The Lungs.=--The lungs themselves, two in number, lie each in a serous
sac or _pleura_, similar in structure to the pericardium and serving
a like purpose. The outer layer of the pleura is reflected back over
the thoracic wall and diaphragm. There is no pleural cavity in health
between the two layers of the pleura, the two surfaces being in close
contact, though moistened with lymph to prevent friction during
respiration. In inflammation of the pleuræ or pleurisy, they become
thickened and roughened and friction results, as is shown by the sounds
heard through the stethoscope. Friction causes effusion and fluid
collects. This generally absorbs again, but occasionally the serous
fluid becomes pustular and _empyema_ results.

In front, between the two pleuræ, which are wholly separate, is the
_mediastinal space_ or _mediastinum_, which extends from the sternum
to the spinal column and contains all the thoracic viscera except the
lungs and heart, that is, the trachea, esophagus, thoracic duct, and
many large vessels and nerves.

[Illustration: FIG. 50.--Diagrammatic representation of the termination
of a bronchial tube in a group of infundibula: _B_, Bronchial tube;
_LB_, bronchiole; _A_, atrium; _I_, infundibulum; _C_, alveoli. (de
Nancrede.)]

Roughly speaking, the lungs begin at the sterno-clavicular articulation
above, the apex coming up above the level of the first rib, and extend
downward together to the fourth cartilage, where the lower margins
gradually separate, the lowest lung limit being the eleventh rib in
the vertebral region. Each lung is conical. The apices extend upward
and the bases, which are broad and concave, rest upon the diaphragm.
The right lung is divided by a fissure into three lobes, the left into
two. The root consists of a bronchus and pulmonary arteries, veins,
lymphatics, and nerves. The tissue itself is composed of an aggregation
of lobules, each consisting of a terminal bronchiole with its alveoli
or air cells, blood-vessels, and nerves, a lung in miniature. The blind
pouches which the air cells surround are called _infundibula_ and are
separated by delicate membranous septa in which lie the capillaries of
the pulmonary artery, thus exposing the blood to the air on two sides.
The lung itself is supplied by the bronchial arteries from the thoracic
aorta and by branches of the sympathetic and pneumogastric nerves.

At birth the lungs are pinkish-white in color but in later life they
are marked with slate-colored patches, due to the deposit in the lung
tissue of particles of dirt breathed in. They are light, spongy, and
highly elastic, and will float in water, crepitating upon pressure
owing to the air in the tissue.

At birth, also, the lungs are solid, so that the first air has to
overcome adhesions between the collapsed walls of the bronchioles and
air sacs, but after they are thus gradually unfolded, in that they are
of extensible material and open to the air above, atmospheric pressure
from within keeps them distended to the full extent of the chest, which
is air tight. They never collapse afterwards unless puncture of the
chest wall, as in stabbing, causes collapse, in which case the lung
shrivels into a small ball.

=Respiration.=--That the organic materials used by the body as food may
give up their energy they must be broken up, and for this oxygen is
needed. The supply of oxygen for the purpose is brought to the tissues
by the blood, which acquires it in the lungs, and the waste product
of combustion, carbon dioxide, is carried off in the same manner. The
lungs are, therefore, adapted to take in large quantities of air and
to keep up a rapid exchange of oxygen and carbon dioxide in the blood.
This process of supplying oxygen to the tissues and of removing carbon
dioxide and other waste is ordinarily an involuntary act, though it can
be regulated temporarily, and is known as respiration or breathing.

There are two periods to respiration: 1. _inspiration_ or the drawing
in of air, and 2. _expiration_ or the expulsion of air from the lungs,
the former process being a little shorter than the latter. A pause
follows each expiration before there is another inspiration. At birth
the normal rate of respiration is 42, but it grows slower as the child
grows older, being 26 at the age of five or six, while in the adult it
averages 17 to 20 times a minute. It is slower during sleep and more
rapid during physical activity. The average amount of air taken in with
every inspiration is 30 cubic inches and the minimum air space per
individual should be 3000 cubic feet per hour.

Breathing is of two kinds, _diaphragmatic_ or _abdominal_ and _chest_
or _rib_ breathing, the former usually being more pronounced in men
than in women, probably because of centuries of tight dressing on the
part of the latter. As a rule, however, both diaphragm and ribs come
into play; for in inspiration, which is an active movement, the thorax
becomes enlarged from before backward, laterally, and vertically.
The ribs are raised by the external intercostals chiefly, though the
internal intercostals aid somewhat, and swinging out upon the vertebræ,
widen the chest as well as deepen it. The diaphragm, which is dome-like
when relaxed, becomes flattened in contraction and so increases the
size of the chest from above downward. As the chest enlarges, the lungs
expand, the air in them becomes rarefied, and more air rushes in.
When the lungs are full they relax and the muscles relax after their
contraction, so that expiration is a passive movement, due largely to
the elastic relaxation of lungs and muscles, the air being driven out
by the lessened capacity of the lungs.

_Difficult Breathing._--In heart and lung troubles, where too little
oxygen is carried to the tissues, dyspnœa or difficult breathing
results and may even advance to _asphyxia_, a condition in which no air
is obtained. In difficult or labored respiration the pectoral muscles
are used in inspiration and the scaleni, which pass from the vertebræ
of the neck to the sternum, develop and become powerful. The levatores
of the ribs may also assist, and even the muscles of the neck and arms
may help out, while in forced expiration the abdominal muscles are
called into play. The glottis opens and closes rhythmically as the air
enters and leaves the lungs, and the nostrils add their mite in the
struggle for oxygen. Finally there may be scarcely a muscle in the body
that is not striving to aid the respiration, and general convulsions
may result, followed by exhaustion and death.

_Air._--In ordinary breathing the lungs are not used to their full
capacity and the air ordinarily used is known as _tidal air_. In forced
inspiration the lungs are filled to their fullest extent and the air
then taken in in excess of the tidal air is known as _complemental
air_. In like manner, the difference between the air ordinarily
breathed out and that breathed out in forced expiration is known as
_supplemental air_. The sum of these three is the _vital capacity_ of
the lungs, while beyond this there is probably some air that is never
expelled, the stationary or _residual air_.

_Respiratory Sounds._--The entrance and exit of the air is accompanied
by respiratory sounds or murmurs, which vary according to their
position in the trachea, the bronchi, or the bronchioles and are
modified in diseases of the lungs and bronchi, when they are often
called _râles_.

_Changes in Air in Lungs._--In passing through the nose and the rest
of the respiratory tract the air is warmed to body temperature and
saturated with moisture. After its entrance into the lungs various
changes take place in it through the mingling of the tidal with the
residual air. Thus, it gives up about 4 or 5 per cent. of its oxygen
and acquires some 4 per cent. additional carbon dioxide, while the
amount of nitrogen remains about the same. By its giving up more oxygen
than it receives carbon dioxide, its volume is slightly diminished.
Exhaled air also contains traces of ammonia and certain organic
matters, generally the results of decomposition, which give a bad odor
to the breath and are more dangerous in a close room than the mere
lack of oxygen or the presence of carbon dioxide. Indeed, the amount
of oxygen may be very much diminished, being reduced even to 5 or 6
per cent. instead of the normal 21 per cent., without being noticed
or giving rise to any immediate bad results. Yet the importance of
ventilation is very evident.

_Effect on Blood._--Respiration causes changes also in the blood,
the venous blood being purple and the arterial bright red. This
difference in color is due to the absence or presence of oxygen, which
is not absorbed or dissolved by the blood but forms a rather unstable
compound, _oxyhemoglobin_, with the hemoglobin of the blood. As the
oxygen is removed in the passage of the blood through the body, there
results in venous blood reduced hemoglobin, which is of a purplish
color. Upon exposure to the air, however, it absorbs oxygen once more
and resumes its scarlet color. If carbon monoxide gets into the blood,
as in cases of gas poisoning, it drives off the oxygen and forms a more
stable compound with the hemoglobin, whence the difficulty in restoring
a person so poisoned.

_Nervous Mechanism._--Nervously, respiration is controlled in three
ways: 1. by the phrenic nerve to the diaphragm; 2. by some fibers
of the vagus or pneumogastric, and 3. by the respiratory center in
the bulbous portion of the spinal cord. Injury to the respiratory
center means the ceasing of respiration and death. Stimulation of the
respiratory center seems to depend upon the character of the blood. If
it is well oxygenized, the breathing is slow and quiet; if there is a
lack of oxygen, dyspnœa results. Probably certain chemical substances
in the blood, which are ordinarily rapidly burned up by the oxygen but
which accumulate in its absence, serve to stimulate the respiratory
center, thus adjusting the effort to get oxygen to the need of it.
Respiration may be stopped by stimulating the mucous membrane of the
nose, as with strong ammonia.

_Variations._--Certain variations from the ordinary respiration might
be mentioned here. A deep inspiration followed by a long expiration is
known as a _sigh_ and a very deep inspiration through the mouth only
as a _yawn_. _Hiccough_ results from a sudden inspiratory contraction
of the diaphragm during which the glottis is suddenly closed. In
_sobbing_ the inspirations are short and rapid with a prompt closing of
the glottis between. Both _coughing_ and _sneezing_ consist of a deep
inspiration followed by complete closure of the glottis and then its
sudden opening and the forcible expulsion of air. Coughing, however,
is generally caused by an irritation or obstruction of the larynx or
trachea and the air is expelled through the mouth, while sneezing is
caused by irritation of the nasal passages and the air is driven out
through the nose. _Laughing_ and _crying_ also resemble one another in
that each is an inspiration followed by a series of short, spasmodic
expirations, during which the glottis is open and the vocal cords in
characteristic vibration. They differ, however, in rhythm and in the
facial expression that accompanies them.

CHAPTER X.

THE ABDOMEN AND THE ORGANS OF DIGESTION AND EXCRETION.

=The Abdominal Cavity.=--Below the diaphragm and separated from the
lowest cavity of the trunk, the pelvis, only by an invisible plane
drawn through the brim of the true pelvis, is the abdominal cavity,
which may be said in a general way to contain the organs of digestion
and the kidneys. It is protected behind by the vertebræ and anteriorly
by the lower ribs above and below by muscular walls, which make
possible the complete bending of the body. These muscles are for the
most part large and very strong and the greater number are inserted,
in part at least, into a median tendinous line, the _linea alba_,
which passes from the ensiform cartilage of the sternum above to the
symphysis pubis below.

=Muscles.=--The _external oblique muscles_ form the outermost layer of
the abdominal wall. They rise from the external surface of the eight
lower ribs on either side and are inserted in the anterior half of the
iliac crest as well as by aponeurosis in the linea alba, where each
joins its fellow from the opposite side, the fibers running downward
and inward like the fingers in the trouser’s pocket. Along the lower
border of the aponeurosis is a broad fold, _Poupart’s ligament_.
The _internal oblique_ rises on either side from the outer half of
Poupart’s ligament and the anterior part of the crest of the ilium
and is inserted into the crest of the os pubis, the cartilages of the
lower ribs, and the linea alba. Its fibers run at right angles to those
of the external oblique. These oblique muscles serve to compress the
viscera, to flex the body, and also assist in expiration.

The deepest of the abdominal muscles is the _transversalis_, which
rises from the outer third of Poupart’s ligament and the adjoining part
of the crest of the ilium, from the six lower costal cartilages, and
by a broad aponeurosis, the _lumbar fascia_, from the lumbar vertebræ.
It is inserted into the pubic crest and by aponeurosis into the linea
alba. There is one of these muscles on either side.

[Illustration: FIG. 51.--Muscles of the trunk from before (left side,
superficial; and right side, deep): 1, Pectoralis major; 2, deltoid;
3, portion of latissimus dorsi; 4, serratus magnus; 5, subclavius; 6,
the pectoralis, sternocostal portion; 7, serratus magnus; 12, rectus
abdominis; 13, internal oblique; 14, external oblique; 15, abdominal
aponeurosis and tendinous intersections of rectus abdominis; 16, over
symphysis pubis; 17, linea semilunaris; 18, gluteus medius; 19, tensor
vaginæ femoris; 20, rectus femoris; 21, sartorius; 22, femoral part of
iliopsoas; 23, pectineus; 24, adductor longus; 25, gracilis. (Dorland’s
Dictionary.)]

The _rectus abdominis_ is also really two muscles and extends from the
symphysis pubis to the cartilages of the fifth, sixth, and seventh
ribs. At first it passes back of the oblique and transversalis
muscles, but about a fourth of the way up it passes in front of the
transversalis and between two layers of the internal oblique, which
thereafter forms its sheath. Its chief duty is to flex the chest on the
pelvis, though it also compresses the abdominal viscera.

One other muscle, a small one, is found in front, the _pyramidalis_,
which rises from the pubic crest and is inserted into the linea alba
midway to the umbilicus.

At the back the open space over the kidneys, between the lower ribs
and the os innominatum, is closed in on either side by the _quadratus
lumborum_, which extends from the three or four lower lumbar vertebræ
and the adjacent iliac crest to the last rib and the upper four
lumbar vertebræ. It flexes the trunk laterally or forward according
as one muscle or both are used, and may aid in either expiration or
inspiration.

The _nerves_ of the abdominal muscles are chiefly the internal
intercostals.

=The Peritoneum.=--Lining the abdominal cavity is a serous membrane,
the peritoneum, which is reflected back over the viscera within in such
a way as to cover each one wholly or in part. Folds of peritoneum,
the _omenta_, connect the stomach with the other viscera, the most
important being the _great omentum_, which has one layer descending
from the anterior and another from the posterior wall of the stomach.
The _mesenteries_ are double layers of peritoneum which hold the
intestines to the vertebræ and posterior wall. Between their folds run
the blood-vessels.

[Illustration: FIG. 52.--Diagram showing the nine regions of the
abdominal cavity: 1, Right hypochondriac; 2, epigastric; 3, left
hypochondriac; 4, right lumbar; 5, umbilical; 6, left lumbar; 7, right
iliac; 8, hypogastric; 9, left iliac. (Ashton.)]

=Abdominal Regions.=--For convenience of description the abdominal
cavity has been divided into nine regions by means of two transverse
parallel lines, the one through the ninth costal cartilages and the
other just over the iliac crests, and two perpendicular parallel
lines through the cartilage of the eighth rib and the middle of
Poupart’s ligament on either side. These nine regions have been named
as follows: The right and left hypochondriac regions up under the ribs
with the epigastrium between, the right and left lumbar regions next
below with the umbilical between, and the right and left inguinal with
the hypogastric between. Others divide it into quadrants by one line
drawn across and another down through the umbilicus. The contents of
the abdomen in full are the stomach, intestines, liver, gall-bladder,
spleen, pancreas, kidneys, suprarenal capsules, and the great vessels,
that is, the organs of digestion and excretion. When distended the
bladder extends up into the abdominal cavity, as does the uterus also
when enlarged.

=Salivary Digestion.=--Although most of the digestive organs are
situated in the abdomen, the food enters the body through the mouth,
where its prehension is a voluntary act. Here digestion also begins and
from the first the process is a double one, mechanical and chemical,
mechanical digestion consisting largely of muscular movements by which
the food is ground up and carried through the digestive tract. Thorough
mastication or grinding of the food by the teeth is necessary, while
the tongue assists by moving the food about and by mixing it thoroughly
with the _saliva_, a viscid fluid composed of water and salts and
having a slightly alkaline reaction. The saliva is secreted by the
parotid, sublingual, and submaxillary glands, and serves to soften and
dissolve the food and by virtue of its unorganized ferment, _ptyalin_,
to convert starch into sugar. Upon proteins and fats it has practically
no digestive action. Moderate warmth and an alkaline medium favor its
action, while extremes of heat or cold or an acid medium hinder it.
There is little absorption in the mouth, though starch, nicotine, and
alcohol may be absorbed in small quantities.

=The Pharynx.=--When the food is ready for deglutition or
swallowing, it is thrust back into the pharynx, a somewhat conical,
musculo-membranous sac, situated, base upward, behind the nose and
mouth and behind, but somewhat above, the larynx. The pharynx is about
four and a half inches long and ends on a level with the cricoid
cartilage in the esophagus or gullet. It is attached to the vertebræ
at the back and opens in front into the mouth. The posterior nares,
the Eustachian tubes, and the larynx also open into it, the last being
protected by the _epiglottis_, which closes during deglutition to
prevent food from entering the air passages, just as the soft palate
is drawn back to prevent regurgitation of food into the nose. There
are three coats to the pharynx: 1. a mucous coat continuous with that
of the mouth and ciliated down to the floor of the nares; 2. a fibrous
coat, and 3. a muscular coat containing among others the constrictor
muscles which serve to carry the food down to the esophagus. Its
arteries are branches of the external carotid and its nerves come from
the spinal accessory and the sympathetic. Occasionally a _foreign
body_ gets lodged in the pharynx just out of reach of the finger and
threatens strangulation. _Retropharyngeal abscess_ on the posterior
wall occurs rarely.

[Illustration: FIG. 53.--Position of the thoracic and abdominal
organs, front view. (Morrow.)]

=The Esophagus.=--From the pharynx the food passes to the cardiac
orifice of the stomach, opposite the tenth dorsal vertebra, through
the esophagus, a muscular tube about nine inches long, which collapses
when empty, its lumen then appearing as a transverse slit. It, too,
has three coats: 1. an inner mucous coat; 2. an areolar coat, and 3.
a muscular coat, the muscles being arranged in two sets, an outer
longitudinal layer and an inner circular layer. By a series of rhythmic
contractions, especially of the circular fibers, the food is pushed
along, though sometimes with liquid food there is no peristaltic action
of the esophagus, the pharyngeal muscles alone sending it to the
stomach. At the lower end of the esophagus an especially strong band
of circular muscle fibers form a sort of sphincter, which prevents the
regurgitation of food. The whole act of swallowing is a reflex, not a
voluntary act and is due to irritation set up by the stimulus of the
foreign body, the food. _Stricture of the esophagus_ is common and
may be of three kinds: 1. spasmodic, occurring in nervous women; 2.
fibrous, due to scar tissue, or 3. malignant, due to cancer.

=The Stomach.=--The stomach is a pear-shaped dilatation of the
alimentary canal, lying under the liver and diaphragm in the epigastrium
and left hypochondrium and connecting the esophagus with the small
intestine. It lies largely behind the ribs, but the greater curvature
is only two fingers’ breadth above the umbilicus and can be manipulated
through the skin. The _cardiac end_, into which the esophagus enters,
is the larger and points upward to the left. The lesser and lower end,
known as the _pylorus_, is at the right and its opening into the small
intestine is guarded by the _pyloric sphincter_. The lesser curvature
is concave and on the upper surface; the greater, convex and on the
under surface. The great omentum is attached to the latter.

In _size_ the stomach varies more or less, that of a man generally
being larger than that of a woman, but it is usually about ten inches
long and four or five inches across. It has a capacity of about five
pints and serves as a storehouse for food.

The stomach has four _coats_: 1. a serous coat derived from the
peritoneum; 2. a muscular coat of three layers with longitudinal fibers
continuous with those of the esophagus, circular fibers, and oblique
fibers; 3. an areolar coat, and 4. a mucous coat, which, when the
stomach is empty, is thrown into longitudinal folds or _rugæ_, and
whose surface is covered with glands, the _gastric glands_, for the
secretion of the digestive fluids.

The _arteries_ come from the celiac axis and the _nerves_ from the
pneumogastric and the solar plexus.

_Ulcer_ and _cancer_ of the stomach are both rather common. In
the former there is apt to be _hyper_-acidity and in the latter
_hypo_-acidity, but the rule does not always hold. In cases of ulcer
there may be hemorrhage and even perforation. Such hemorrhage can be
distinguished from hemorrhage from the lungs by its slightly acid odor
and by the frothy character of hemorrhage from the lungs. There is much
irritation at the pylorus and where there is irritation there is liable
to be cancer.

=Gastric Digestion.=--In the stomach the food is churned and thoroughly
mixed with the gastric juices, and it is also subjected to a propulsive
movement that drives it on to the intestine. When it comes to the
stomach it is semi-solid and when it has become fluid or semi-fluid, in
which state it is known as _chyme_, it is ready to pass on. Before it
can do so, however, it must overcome the strong pyloric sphincter, and
this it does by the muscles about the sphincter pushing it constantly
on until the sphincter gives way. Probably most of the propulsive
movements take place within a few inches of the pylorus.

The _gastric juice_ is secreted by glands in the wall of the stomach
and poured out through little tubules which project from the surface.
It is a thin, almost colorless fluid with a sour taste and odor due
to the presence of free _hydrochloric acid_, an important element in
digestion. Probably when the stomach is empty and for some twenty
minutes after the appearance of food there is no hydrochloric acid
present and, the food being alkaline, salivary digestion continues.
Then, called forth by the presence of the food, the hydrochloric acid
appears and salivary digestion ceases in the acid medium. Little
digestion of starches or fats takes place, the chief action being
on proteins, which are converted into soluble peptones. For besides
hydrochloric acid the gastric juice contains two ferments: 1. _pepsin_,
which is particularly active in aiding the digestion of proteins, and
2. _rennin_, which especially affects milk. Neither hydrochloric acid
nor pepsin seems capable of digesting food alone, but each is essential
to the other. They are secreted by different types of cells, secretion
depending upon the nerve supply and upon the presence of food. Gastric
digestion is favored by minute subdivision of the food and by the
right proportion of hydrochloric acid, which should be 0.2 per cent.
Body temperature is also advantageous. Except that proteins are put in
solution and partly digested, little digestion goes on in the stomach,
and though the rugæ afford a large absorbing surface, little absorption
takes place, although more takes place than in the mouth and in time
most foods, except fats, can be absorbed. The time of digestion varies
with different foods and in different people, but probably three to
five hours are necessary. The food leaves the stomach as _chyme_, a
fluid of about the consistency of pea soup.

_Vomiting_ is more or less the reverse of swallowing and is generally
preceded by a feeling of _nausea_, which starts up _retching_, a more
or less involuntary effort of the stomach to throw off its contents.
To relieve the retching a long breath is taken, followed by a deep
expiration that opens the cardiac end of the stomach and allows the
abdominal muscles to force the food out. After much vomiting and
prolonged retching the pyloric end of the stomach may be affected and
bile will then appear in the vomitus. _Artificial vomiting_ may be
produced by irritation of the gastric nerve center in the brain or by
irritation of the stomach itself.

[Illustration: FIG. 54.--The intestinal canal: 1, Stomach; 2, duodenum;
3, jejunum; 4, ileum; 5, cecum; 6, vermiform appendix; 7, ascending
colon; 8, transverse colon; 9, descending colon; 10, sigmoid flexure;
11, rectum. (Leidy.)]

=Intestinal Canal.=--From the stomach the food passes into the
intestinal canal, a convoluted tube which extends from the stomach to
the anus and in which, more particularly in the upper portion, the
greater part of the digestion and absorption of food takes place. This
tube, which is about six times the height of its possessor, consists of
two parts, the small and the large intestines, the first four-fifths,
or about 25 feet, being small intestine. It occupies the central and
lower parts of the abdominal cavity and a small portion of the pelvic
cavity, and is attached to the spine by the mesentery, which, however,
allows great freedom of motion, so that there is little fixation to the
loops of the small intestines.

=The Small Intestine.=--The small intestine opens out of the stomach
and has three divisions: 1. the _duodenum_, which is only about ten to
twelve inches long; 2. the _jejunum_, so called because it is generally
empty after death, which is about two-fifths of the remainder and lies
chiefly in the umbilical region and the left iliac fossa, and 3. the
_ileum_ or _curved intestine_, the remaining three-fifths, which gets
its name from its numerous coils and which lies in the middle and the
right side of the abdomen. There is no direct division between the
jejunum and the ileum, but the first part of the former and the last
part of the latter are quite different in character. At its entrance
into the large intestine the ileum is guarded by the _ileo-cecal valve_.

[Illustration: FIG. 55.--1, Central lacteal; 2, capillary network; 3,
columnar cells.]

The same _coats_ continue in the small intestine as were found in the
stomach, but they are here much thinner and the inner coat is shaggy,
like velvet, with innumerable minute processes called _villi_, which
greatly increase the absorbing surface. In fact, the great length of
the intestine as well as the presence of the villi is aimed to provide
a large surface to absorb the food as it passes, an even greater
increase of surface being provided by the fact that the intestinal wall
is thrown into folds, the _valvulæ conniventes_. Each villus is covered
with a layer of columnar epithelial cells and has within connective
tissue, in which are found a fine capillary network and open lymph
spaces from which leads a single lacteal vessel.

Closely connected with the lymphatic vessels are the _solitary glands_,
small round bodies the size of a small pin’s head. _Peyer’s glands_
or _patches_ are patches of solitary glands opposite the mesenteric
attachment and are largest and most numerous in the ileum. In typhoid
fever they are involved and may become the seat of ulcers. There are
also the _glands of Lieberkühn_ which secrete the succus entericus.

The _arteries_ of the small intestine, which include the superior
mesenteric, are from the celiac axis and the _nerves_ are from the
superior mesenteric plexus of the sympathetic. The _veins_ empty
chiefly into the portal system.

The _movements_ of the intestine, like those of the esophagus, are
peristaltic, but the action is complicated by the fact that the tube is
not straight but in coils.

=Intestinal Digestion.=--The food, which enters the duodenum as chyme,
there comes in contact with the bile and the pancreatic juice, which
together but unmixed enter the duodenum from their respective ducts
by a common orifice. As in the stomach, the digestive juices are
called forth by the presence of food. The _bile_ is secreted in the
liver, from which it flows away through the hepatic duct, which joins
the cystic duct from the gall-bladder to form the common bile duct.
Through this it flows into the intestine during digestion, but between
whiles it passes up into the gall-bladder, where it is stored for
future use and whence it is expelled when needed. When pure it is a
thick, viscid liquid, varying from a bright red to a greenish-yellow in
color according to the pigments present, and of an alkaline reaction.
It consists chiefly of the bile pigments, _biliverdin_, which gives
the green color, and _bilirubin_, which gives the red color, and of
bile salts in solution, _cholesterin_, which probably forms the basis
of many gall stones, is also present. Bile is a disinfectant to the
bowel and a lubricant for the feces. How much digestive action it has
is a question, but it affords the necessary alkaline medium for the
pancreatic juice to act in.

The _pancreatic juice_ is secreted by the pancreas, from which it
enters the intestine through the pancreatic duct, and is probably the
most important fluid in the digestive process. It is clear, practically
colorless, slightly viscid or gelatinous, and quite strongly alkaline
in reaction, owing to the presence of sodium carbonate. It contains
three ferments, _amylopsin_ for the digestion of starch, _trypsin_ for
the digestion of proteins, and _steapsin_ for the digestion of fats.
By it, as by the saliva, starch is turned into sugar or maltose, in
which form it is absorbed, while proteins are converted into peptones,
as they are in the stomach. Since, however, fats are acted on nowhere
else, the chief function of the pancreatic juice may be considered
to be the digestion of fats. Having broken through their albuminous
envelope, it divides them into glycerine and fatty acids and then
emulsifies them with the assistance of the bile.

The food also comes in contact with the _succus entericus_, a juice
secreted by the glands of Lieberkühn in the small intestine, whose
chief action is the conversion of sugar into glucose.

=Absorption.=--As the food is absorbed from the intestine it is
liquid and entirely digested and is known as _chyle_. Practically all
absorption takes place from the small intestine, though there is a
little in the large intestine. It takes place in two ways: 1. through
the portal vessels and 2. through the _lacteals_, which are the
lymphatic vessels of the small intestine. Fats are absorbed practically
entirely by the lacteals. They enter the cells covering the villi,
travel thence to the lymph spaces, and so into the lacteal or main
lymph channel, whence they are carried to the thoracic duct and the
general circulation. From the blood they are absorbed as fat and stored
up as adipose or fatty tissue, which is found throughout the body in
connective tissue about the organs. Organic salts and water are for
the most part absorbed by the portal system, which they reach through
the capillaries of the villi and through which they go to the liver.
Starches, in the form of sugar, pass between the cells of the villi
into the lymph spaces, from which they are taken up by the capillaries.
On the way to the liver maltose becomes dextrose. Proteins, in the form
of peptones, pass through the layer of epithelial cells to the lymph
spaces and then to the capillaries, an active part being taken by the
cells. By the time they reach the liver the peptones have been changed
back into proteins. In fact, peptones seem to have some poisonous
effect upon the blood if they get into it as such.

=The Large Intestine.=--The large intestine differs from the small
in size and in fixity of position, lying curved in horseshoe shape
above and around the small intestine. It is five or six feet long,
large in caliber, and is thrown into crosswise folds. It has the same
four _coats_ as the small intestine, but the mucous coat is pale and
smooth, without villi. Its _glands_ are the crypts of Lieberkühn and
the solitary glands. The _arteries_ are branches of the superior and
inferior mesenteric and the _nerves_ come from sympathetic plexuses.

The blind sac lying in the right iliac fossa, with which the large
intestine begins, is called the _cecum_, and into this the ileum
opens, the ileo-cecal valve preventing regurgitation. Just below the
ileo-cecal opening is the _vermiform appendix_, a narrow, worm-like
tube with a blind end, varying in length from one to nine inches, but
generally about four and one-half inches long, which, so far as is
known, is functionless as well as dangerous. People have been born
without an appendix and it has in rare instances grown again after
operation. Its base is located in the living by _McBurney’s point_, a
point two inches from the anterior superior spine of the ilium on a
line drawn from the spine to the umbilicus.

From the cecum the intestine ascends in what is known as the _ascending
colon_ along the abdominal wall at the right to the under surface of
the liver, where it turns in the _hepatic flexure_ abruptly across
the body to the left, passing below the liver, stomach, and spleen
in the _transverse colon_. In the _splenic flexure_ it turns down
the left abdominal wall, the _descending colon_ passing to the crest
of the ilium, where there is another curve, the _sigmoid flexure_,
leading to the _rectum_, which passes for six or eight inches down
along the vertebræ, a little to the left, to the _anus_, the external
opening. This opening is guarded by two _sphincter muscles_, about an
inch apart, the internal and external sphincters. The coils of the
small intestine lie below the transverse colon, covered mostly by the
omentum. The splenic flexure is behind the stomach and below the spleen
and is slightly higher than the hepatic flexure. The sigmoid flexure
can be felt in the left inguinal region in thin people.

The fact that the _rectum_ is somewhat to the left is of importance in
childbirth because if the rectum is packed, it may turn the child’s
head in the wrong direction.

No digestion goes on in the large intestine, the function being to
dry by absorbing water. The _movements_ are practically the same
as those of the small intestine except that they are much less
active. Fermentation makes the contents acid. By the time food
reaches the rectum it has been thoroughly digested and has given up
its nourishment. It is then expelled as waste matter or _feces_.
_Defecation_ combines the involuntary movements of peristalsis and
relaxation of the sphincters with the voluntary aid of the abdominal
muscles. The _ano-spinal reflex_, by which movements of the bowel are
regulated, is in the lumbar enlargement of the cord.

The _hemorrhoidal veins_ in the lower rectum are connected with both
the systemic and the portal veins and have no valves so that, as they
are subjected to much strain, they often become varicose and dilated.
This condition is called _hemorrhoids_ or _piles_. _Obstruction_ of
the intestine may be caused by the growth of a constricting band, by
_intussusception_ or telescoping of the intestine on itself, especially
at the ileo-cecal valve, or by _volvulus_ or twisting. _Foreign bodies_
are sometimes found in the appendix but they are not usually the cause
of appendicitis. _Cancer of the intestine_ is common and its mass
is apt to cause obstruction with all its attendant symptoms. It may
necessitate an artificial anus. _Hernia_ or _rupture_ may also occur
and the hernia may become strangulated.

=Food and Metabolism.=--Anything serves as food that replaces or
hinders the loss to which the component parts of the body are liable.
Proteins, carbohydrates, fats, some mineral matters, as salt and
perhaps iron, and water are needed. The energy once expended by plants
or animals in the formation of the materials which serve as food is set
free in the body by the breaking up of these complex substances into
their original elements, which are then recombined into the complex
materials needed for the body’s life and growth. This process of
building up complex materials from simple ones is known as _anabolism_
and that of breaking them down as _katabolism_, while the two combined
form the complete cycle of _metabolism_. Those foods have the best
value that give up their energy most readily. For their combustion,
heat, oxygen, and water are needed. Hunger indicates that the supply of
material for katabolism has been used up and that more is needed, just
as thirst indicates the need of the system for more fluids.

The proteins or nitrogenous foods include all animal foods except fats,
fish, crustaceans, eggs, milk and its products, certain vegetables,
especially the lentils, that is, peas and beans, and gelatine. The fats
include various fats and oils commonly eaten. The carbohydrates are
the starchy foods, as cereals, sugars, fruits, and most vegetables,
in fact, practically all except the lentils. Various beverages and
condiments have no great nutritive value but serve to stimulate the
appetite and to excite the secretion of the digestive juices. Coffee,
tea, and alcohol are stimulants.

The different classes of foods have different functions in the
nourishment of the body. The proteins are primarily tissue-builders
and also help somewhat in force production. The fats are essentially
heat-producers, though they too help in force production. The
carbohydrates are chiefly important as force-producers, though they
also produce heat and to a certain extent save protein oxidation. Fat
is formed by all three but only in small amount by proteins. So no one
food can form the whole diet but there must be variety. Carbohydrates
and fats are not sufficient for life, some protein is necessary.
Carbohydrates are more digestible than fats but have less potential
energy. Gelatine saves waste of nitrogen, though it does not increase
the supply. Water and salts are not nutritive but they aid the body
processes, the water helping to dilute and dissolve substances for
digestion.

The end-product of the consumption of protein is _urea_, which is
eliminated by the kidneys. Just where it is formed is unknown, but many
think in the liver. A trifling amount of urea is also eliminated in
the sweat and in the breath as well as in the feces. Proteins increase
nitrogenous metabolism and also the metabolism of other foods, but the
amount of nitrogen eliminated is just equal to that taken in. Probably
some comes from the tissues themselves and not from the food. The
oxidation of carbohydrates and fats is measured by the amount of carbon
excreted. At first as much is given off as is taken in, but after a
while the carbohydrate is stored up as glycogen in the liver and the
fats are stored as fat.

The amount of food needed varies with the person’s size and occupation,
less being needed for a child than for an adult and more for a
hard-working man than for one who is doing less work. In general, 100
to 130 grams of protein, 40 to 80 grams of fat, 450 to 550 grams of
carbohydrates, 30 grams of salts, and 28,000 grams of water is a fair
amount.

Foods are cooked to make them more digestible and to develop their
flavor, so that they will taste better. Cooking also kills germs and
parasites that might be harmful. Meats should be cooked rapidly on
the outside to coagulate the surface albumen and keep in the juices.
The heat, besides coagulating the albumen, turns the tough parts to
gelatine. In cereals the tough envelope of cellulose is broken up
and in vegetables the tough fibrous parts are softened and made more
digestible.

=The Liver.=--Below the diaphragm on the right and extending across
above the stomach, resting in a way upon the transverse colon and the
small intestine, is the liver, the largest gland in the body. It is
dark reddish-brown in color and is larger in proportion in the child
than in the adult. The upper surface is convex and lies in contact
with the diaphragm, while the lower surface is concave to fit over the
organs beneath. With a full breath it comes downward and forward, with
the edge against the abdominal wall, and can be easily felt. Numerous
strong ligaments, including the suspensory ligament from the diaphragm,
hold it in place, and it is more firmly fixed than any other of the
abdominal organs, probably on account of its large size. It is divided
by fissures into five _lobes_, of which the most important are the
right and left, the right one being the largest and containing the
gall-bladder in one of its fissures.

[Illustration: FIG. 56.--The liver, seen from below. 1, Inferior vena
cava; 2, gall-bladder. (Morrow.)]

The liver tissue contains a large number of _cells_ collected into
_lobules_, in the center of each of which is a blood-vessel, the
_intralobular vein_, from which a network of capillaries extends to
the edge of the lobule, there being a capillary on either side of each
row of cells. Between the cells also are the _intercellular biliary
passages_, roots of the bile ducts which exist in the connective tissue
between the lobules and which join to form two main ducts, one from
the right and the other from the left lobe. By the union of these two
ducts the _hepatic duct_ is formed, which, after a course of one or two
inches, joins the cystic duct from the gall-bladder to form the _ductus
communis_ or _common bile duct_.

The liver has a double _blood supply_, the _hepatic artery_ from the
celiac axis bringing nourishment to the connective tissue and the walls
of the blood-vessels, while the capillaries between the cells come from
the _portal vein_, which, being formed by the junction of the superior
and inferior mesenteric, the splenic and the gastric veins, contains
the proteins and carbohydrates absorbed during digestion. After its
passage through the liver this blood from the portal vein is collected
once more into the hepatic veins, which convey it to the inferior vena
cava. During its passage, however, various changes take place, for the
liver plays an important part in the metabolic processes of the body.

The liver has two principal _functions_, the secreting of bile and
the storing up of glycogen. The secretion of _bile_, which is a very
important aid to digestion, is probably a reflex act, the presence of
peptones in the portal blood after meals acting as a stimulant to the
liver cells. For food at once increases the secretion of bile, which
is poured from the cells into the small bile ducts and finally passes
into the hepatic duct and so to the gall-bladder, where it is stored
until needed. Although the flow from the liver is constant, the amount
secreted reaches its maximum when the food gets down into the small
intestine, that is, four or five hours after eating, there being a
lull before that. Apart from the process of secretion, the manufacture
of the bile pigments, _bilirubin_ and _biliverdin_, which are made from
the hemoglobin of the blood, seems to require some special action on
the part of the liver cells.

The _glycogen_, which is manufactured and stored in the liver cells,
is a clear hyaline substance, akin to starch and capable of being
converted into sugar by the starch ferment. Probably there is some
such ferment in the blood which converts the glycogen into sugar as
soon as it passes from the liver into the blood, though what it is,
is not known. Neither is it known just how glycogen is formed, but
it is manufactured chiefly after a mixed meal in which carbohydrates
predominate, proteins having little and fats no effect upon its
formation. It is undoubtedly formed from the sugar in the portal blood
and the process requires some work on the part of the liver cell
itself. Probably there is always some sugar in the circulating blood
which, as it is used up, must be made good. If there it not enough in
the diet, the liver supplies the deficiency from its store of glycogen.

Glycogen is found also in the muscles, in the placenta as food for the
fetus, in leucocytes, and to a slight extent in cartilage. In fact, it
is the form in which carbohydrate material is supplied to the tissues
as needed. Normally, much of the sugar is used up by the blood and
its cells in metabolism, giving rise to heat and energy. In muscles
glycogen is probably digested as lactic acid, as before action muscle
is neutral or slightly alkaline and after action acid.

When the liver is deranged and allows the glycogen to pass out into the
blood too freely, or when the glycogen is not held as such but turned
to sugar and passed out in large quantities, _sugar in the urine_ or
_diabetes mellitus_ results.

Besides its secreting function the liver has an _eliminative function_
and plays an important part in purifying the blood, removing from
it many poisonous and narcotic substances. It is thought by some,
though it has not been proved, that _urea_, the end-product of protein
metabolism, which is brought by the blood to the kidneys and there
excreted, is formed in the liver. At any rate, urea is formed not only
from the nitrogenous food eaten but from the metabolism of protein
substances in the tissues, being purely a waste product, from which
the nutritious substances have been absorbed. The amount thrown off is
an accurate gauge of the amount of protein metabolism going on. The
process of its manufacture is doubtless very complex.

_Ptosis_ or _dropping_ of the liver sometimes occurs and is due to the
stretching of the ligaments. _Rupture_ is common, generally as the
result of a fall from a height, on account of its size and friability.
The liver is also subject to many diseases. _Cirrhosis_ occurs in
people who drink a good deal and in its later stages is accompanied by
_ascites_, an accumulation of fluid in the abdominal cavity. When there
is a general accumulation of fluid throughout the body it is known as
_anasarca_. _Syphilis_ causes enlargement of the liver. _Abscesses_
occur, perhaps oftener in the tropics than farther north, and may break
into the lungs, stomach, or intestine.

=The Gall-bladder.=--The gall-bladder, which is simply a reservoir
for the bile, is a pear-shaped organ three inches long and one inch
broad. It lies in a fossa on the under side of the liver, with the
large end or fundus touching the abdominal wall just below the ninth
costal cartilage. Here it can be felt as a small mass in empyema of
the gall-bladder. Normally it holds a little over one ounce, but with
occlusion it may become stretched. Its duct is the _cystic duct_, which
joins the hepatic duct in the common bile duct, but bile only passes
up into the gall-bladder when the opening into the duodenum is closed,
that is, between meals.

If one of the bile ducts is stopped up by a stone or cancer or for
any other cause, the bile backs up in the liver, the pigments are
absorbed into the circulation, and _jaundice_ results. In this
condition operation is dangerous, as the time of coagulation of the
blood, normally five minutes or less, is much delayed. _Gall stones_,
formed largely of bile pigments and cholesterin, sometimes collect in
the gall-bladder, where they cause irritation and may give rise to
_empyema_ of the gall-bladder. The stones vary in size from a pea to a
hen’s egg and when small may be very numerous.

[Illustration: FIG. 57.--The pancreas, spleen, gall-bladder, etc.,
showing their relations. (After Sobotta.)]

=The Pancreas.=--Another accessory organ of digestion is the pancreas,
the _abdominal salivary gland_, as it is sometimes called on account
of its close resemblance to the parotid gland. This is a grayish-white
racemose gland, six and a half inches long by one and a half inches
wide and one inch thick, lying behind the stomach on a level with the
first and second lumbar vertebræ and shaped like a pistol with its
handle toward the right. In an emaciated person it can be felt. The
_pancreatic duct_ runs the whole length of the gland from left to right
and conveys the _pancreatic juice_ from various little glands in the
substance of the organ to the duodenum, into which it empties along
with the common bile duct by a common orifice. The _arteries_ are from
the celiac axis and superior mesenteric, the _veins_ belong to the
portal system, and the _nerves_ come from the solar plexus.

Surgically the pancreas is of no special importance, though _acute
pancreatitis_ does occasionally occur and is a very serious condition
and one hard to diagnose.

=The Spleen.=--The largest and most important of the ductless glands
is the spleen, an oblong, flattened organ lying deep in the left
hypochondriac region between the stomach and diaphragm above the
descending colon, and corresponding to the ninth, tenth, and eleventh
ribs. It is soft, brittle, and very vascular. Its _artery_ is a branch
of the celiac axis and the _vein_ belongs to the portal system. Its
_nerves_ are the pneumogastric and branches from the solar plexus. The
_function_ is not well understood but probably it is connected with or
related to the vascular system in some way. Perhaps it manufactures
blood corpuscles.

The spleen varies more in size than any other organ. Normally it cannot
be felt, but in typhoid it usually can. It is generally atrophied in
old age and hypertrophied in almost all acute infectious diseases,
especially in typhoid fever and malaria. In leukemia it is often
greatly enlarged. Sometimes in violent falls it is _ruptured_ and there
is considerable hemorrhage.

=The Suprarenal Capsules.=--The other ductless glands, the suprarenal
capsules, yellowish triangular bodies, are situated just above and
in front of the kidneys. Their function is important but not well
understood. Death, accompanied by great muscular weakness, follows
the removal of both, and when they are diseased, similar weakness is
observed and the skin becomes bronzed. Injection of the extract of
the suprarenals stimulates the muscular system. So probably they
secrete into the blood minute quantities of a substance or substances
beneficial to the body, especially to the muscular system.

[Illustration: FIG. 58.--Diagram of the relation of kidney to viscera,
spine, and surface points. (American Text-Book of Surgery.)]

=The Kidneys.=--The two kidneys lie on either side of the vertebræ at
the back of the abdominal cavity and behind the peritoneum, between the
last dorsal and the third lumbar vertebræ, their inner edge being about
one inch from the spinous processes. They are bean-shaped, four inches
long, two inches wide, and one inch thick, and are embedded in a mass
of fat and loose areolar tissue. They can be felt only when misplaced
or when enlarged, as by tuberculosis or malignant disease.

The whole kidney is enveloped in a fibrous _capsule_ which normally
may be peeled off but which in some diseases becomes adherent. On the
internal border is a _fissure_ or _hilum_, through which pass the
blood-vessels and the ureter. Upon entering, the ureter dilates into
a sac, the _pelvis of the kidney_, into which project the _Malpighian
pyramids_ of the _medullary substance_, a substance made up of the
straight uriniferous tubules and blood-vessels. Outside the medullary
substance and just under the capsule is the _cortex_, containing the
_Malpighian bodies_, blood-vessels, and the _convoluted tubules_ or
_loops of Henle_. Each Malpighian body contains within a capsule a
plexus of capillaries, the _glomerulus_, with an afferent arteriole and
an efferent vein. The _renal artery_ is a branch of the aorta and the
_nerves_ are from the solar plexus.

[Illustration: FIG. 59.--A longitudinal section of the kidney. (Leroy.)
_a_, Renal artery; _c_, cortex; _m_, medulla; _u_, ureter.]

[Illustration: FIG. 60.--A Malpighian body or corpuscle. (Leidy.)
_a_, Afferent artery; _e_, efferent vessel; _c_, capillaries; _k_,
commencement of uriniferous tubule; _h_, uriniferous tubule.]

_The Urine._--As the blood passes through the glomeruli, the urine is
filtered off as it were, probably by a process of transudation rather
than simple filtration. The cells lining the tubules also play an
important part in its formation, not by secreting new substances but
by taking up those brought by the blood and discharging them into the
convoluted tubules, from which the urine passes through the straight
tubules of the medulla to the pelvis, to be carried thence by the
ureter. The process of the formation of the urine, therefore, is not
purely a process of secretion but requires some action on the part of
the kidney, though no new substances are secreted in the kidney.

The passage of the urine down through the ureters is assisted by a kind
of peristaltic action in the walls of the ureters and it is expelled
from the body by the act of _micturition_, which is mostly voluntary,
though a certain amount of nervous mechanism controls it. The seat of
this nervous mechanism is in the lumbar enlargement of the spinal cord.
In some nervous conditions, especially where there is injury to the
spinal cord, there is _involuntary micturition_.

The urine is a watery solution containing many waste products,
especially urea. It is generally amber in color, varying in shade with
circumstances, with an aromatic, characteristic odor when fresh. It
is acid in reaction and has a specific gravity of about 1020, though
this too varies with circumstances. Besides water, which is its chief
constituent, it contains urea, uric acid, organic acids, urates,
inorganic salts, including sodium chloride and phosphates of calcium
and magnesium, a certain amount of ammonia, and certain pigments. Its
acidity is due to acid sodium phosphate in solution but varies with the
food, and in disease the urine may become alkaline when passed. After
standing a few hours in a warm place it decomposes and becomes alkaline.

The quantity, which is normally three pints or fifteen hundred cubic
centimeters in twenty-four hours, varies with the amount of fluid
drunk, the amount of perspiration, etc. The amount secreted depends
chiefly, however, upon the flow of the blood through the kidneys; the
greater the flow of blood, the larger the amount of urine formed; and
the blood flow is determined by blood pressure and by vasomotor action.
Secretion also seems to be increased by the presence of urea, which
apparently serves as a stimulant to the kidney cells.

The excretion of waste materials takes place by three main channels,
the lungs, skin, and kidneys, and the materials are of four kinds,
_urea_, _carbon dioxide_, _salts_, and _water_. The lungs carry off
carbon dioxide and water chiefly, the skin these and inorganic salts,
while the kidneys eliminate practically all the urea as well as
inorganic salts and water. When the kidneys are not working the skin
carries off much urea. In fact, a close relationship exists between the
kidneys and the skin in the matter of excretion. Thus, with increased
perspiration in warm weather comes decreased urine, while in cold
weather the blood is sent in and the urine increased in amount.

To incite action of the kidneys drugs known as _diuretics_ may be used.
These act in two ways, by stimulating the kidney cells directly and by
acting on the general circulation or nervous system. Any emotional or
nervous excitement increases the flow of urine.

There are certain abnormal constituents of urine, of which the two most
important are _albumen_ and _sugar_. The former is found only when
there is some disturbance of the kidneys, ureters, or bladder, and its
presence usually denotes some change in the cells lining the urinary
tract. It may occur in congestion of the kidney as well as in disease.
Sugar is found only in _diabetes_, the amount varying with the severity
of the disease. In _jaundice_ certain bile pigments are present in the
urine, giving it a dark brown color and to the foam a greenish-yellow
color. Even normal urine has some sediment upon standing, consisting
of cells from the urinary tract and mucus. In very acid urine after
standing a heavy sediment, whitish or pinkish, _i.e._, brick dust, in
color, is thrown down. It does not necessarily denote disease, but
shows the urine is acid and concentrated. In _alkaline urine_ there is
a sediment due to phosphates.

_Rupture_ of the kidney occurs but is not so serious as rupture of
the liver or spleen because the kidney is situated outside of the
peritoneum. It necessitates the removal of the kidney, however, and
when for any reason one kidney is removed the other increases in size
and does double work to compensate for the loss. Removal of both
kidneys means death. Sometimes the kidney becomes loose and moves
about, a condition known as _floating kidney_. _Perinephritic abscess_
is abscess in the loose fatty tissue about the kidney.

[Illustration: FIG. 61.--The urinary organs viewed from behind.]

=The Ureters=, one for each kidney, are tubes the size of a goose
quill and about fourteen inches long, extending from the hilum of the
kidney to the base of the bladder. They have three _coats_, an internal
mucous, a muscular, and an external fibrous coat, this last being
continuous with the cortex of the kidney and the fibrous tissue of the
bladder. In the female the ureters may be felt through the wall of the
vagina as they come into the bladder. In tubercular disease of one
kidney the ureter becomes inflamed and enlarged and through the vagina
feels almost like a lead pencil, a sure diagnostic sign.

=The Bladder and Urethra.=--In their course to the bladder the ureters
pass from the abdominal into the pelvic cavity, but before describing
the pelvis itself it will be well to complete the account of the
urinary organs by considering the bladder and urethra. The _bladder_ is
the reservoir for the urine and has muscular walls lined with mucous
membrane. A peritoneal coat covers the upper surface and is reflected
to the walls of the abdomen and pelvis. It is situated back of the os
pubis, the front bone of the pelvis, with its base or fundus directed
downward and backward. Normally it is in the pelvis, but when much
distended it mounds up into the abdominal cavity, where it can be
felt in front as a tumor. It rests on the rectum in the male and on
the cervix in the female and is held in place by numerous ligaments.
When empty it may be Y-shaped, but it becomes oval when distended. Its
capacity is about one pint.

The lower abdominal wall and the anterior wall of the bladder may be
wanting congenitally. In paralysis of the sphincter at the neck of the
bladder distention results. _Stones_ may be found in the bladder.

From the neck of the bladder the urine passes out of the body through
the _urethra_. This in the male passes down through the penis and is
about ten inches long. Except when urine is passing it is a transverse
slit with the upper and under surfaces in contact, while at the end of
the penis the slit of the meatus urinarius is vertical. When the penis
is flaccid, the urethra describes a sharp curve before its entrance
into the bladder, but it becomes approximately straight when the penis
is raised at right angles to the body--an important point to remember
in catheterization.

In the female the urethra is straight and much shorter, being only
about one and a half inches long. The _meatus urinarius_ is in the
anterior vaginal wall about one inch behind the clitoris.

Sometimes the urethra is _ruptured_ in a fall. _Stricture_ of the
urethra occurs sometimes after gonorrhoea, owing to the formation of
scar tissue following ulcer.

CHAPTER XI.

THE PELVIS AND THE GENITAL ORGANS.

=The Pelvis.=--Before taking up the pelvic organs, the pelvis itself
should be described. The name pelvis has been given to the bony ring
which is interposed between the spine and the femurs on account of its
resemblance to a basin. At the back of this basin or pelvis are the
_sacrum_ and _coccyx_, already described in connection with the back,
and at the sides and meeting in the median line in front are the two
_ossa innominata_ or _nameless bones_, so called on account of their
peculiar and indescribable shape. At birth each os innominatum is made
up of three bones, the _ilium_, _ischium_, and _pubes_, but about the
age of puberty the three become welded into one. At their point of
junction is the cavity of the acetabulum for articulation with the head
of the femur or thigh bone.

[Illustration: FIG. 62.--Front view of the pelvis, with its ligaments.
(Dorland.) _a_, Anterior sacro-iliac ligament; _b_, iliofemoral
ligament; _c_, obturator membrane; _d_, symphysis pubis; _e_,
sacro-sciatic ligament.]

[Illustration: FIG. 63.--The right innominate bone. (After Toldt.)]

The upper, expanded portion of the os innominatum is the _ilium_,
whose upper border is known as the _crest_ and which has two _spinous
processes_ front and back, a superior and an inferior, the superior
spine being in each case the larger. These spines, especially the
anterior superior spines, and the crest give attachment to many
muscles, and to the outer surface of the bone the gluteal muscles are
attached. The anterior superior spine is also important in making
measurements to ascertain whether both legs are of equal length.

Below the ilium posteriorly is the _body of the ischium_, which has on
its lower edge a tuberosity, the prominent bone on which one sits. Near
the upper edge is the _spine_ of the _ischium_, between which and the
posterior inferior spine of the ilium is the greater _sacro-sciatic
notch_ for the passage of vessels and nerves, including the sciatic
nerves. From the tuberosity the ramus extends forward below the
_obturator foramen_, a large opening between the ischium and the pubes,
also for the passage of vessels and nerves, to meet the pubes, the last
and smallest of the three bones which go to make up the os innominatum.

The anterior surface of each _pubes_ presents a crest, ending
externally in a spine, and the two pubic bones join in front in the
_symphysis pubis_. The bone gets its name from the growth of pubic
hairs over this region at puberty.

[Illustration: FIG. 64.--Diameters of the pelvis: _d_, antero-posterior;
_o b_, oblique; _t r_, transverse. (de Nancrede.)]

Anteriorly the ossa innominata support the external organs of
generation, while within are the internal organs of generation. On the
inner surface of the ilium, slightly above the level of the acetabulum,
is the _ileo-pectineal line_, above which lie the _iliac fossæ_. A
plane drawn through the prominence of the sacrum, the ileo-pectineal
lines, and the upper margin of the symphysis pubis serves to divide
the upper or false pelvis from the lower or true pelvis. The _false
pelvis_, which is the larger, serves to support the intestines and
to take part of the weight from the abdominal walls, while the _true
pelvis_, being more surrounded by bone and so capable of affording
more protection, guards the internal organs of generation. The lower
circumference of the pelvis is known as the _outlet_. In the female the
bones are lighter, the sacrum less curved, and the diameters greater
than in the male.

On the whole, the pelvic bones are well covered in with muscles. The
anterior superior spine, however, is easily felt in front and the whole
crest can be felt back to the posterior superior spine. The tuberosity
of the ischium also can be felt, especially when the thigh is flexed,
for it is largely uncovered of muscles. The spine of the os pubis can
always be felt, on a level with the great trochanter, and the relation
of its position to that of a hernia shows whether the rupture is above
or below Poupart’s ligament, that is, whether it is inguinal or femoral.

Occasionally there is lack of development of the pubic bones for two
or three inches and the bladder is exposed. _Fracture_ of the pelvis
may occur, perhaps with injury to the viscera. The acetabulum may
be fractured or the sacrum broken, with injury to the sacral plexus
of nerves, causing paralysis of the lower extremities and of the
sphincters, with resultant involuntary passage of urine and feces, and
in childbirth the coccyx is often broken. In _rickets_ there may be
great deformity of the pelvis, causing trouble in childbirth later in
life. _Osteomalacia_ is a disease of adults, in which the bones are
soft and the weight pushes the promontory of the sacrum forward and
approximates the sides of the pelvis.

=The Male Generative Organs.=--The male generative organs consist of
the prostate gland, testes, and penis.

The _prostate gland_ is shaped like a small horse-chestnut and is
composed of numerous glands from which come a dozen or more excretory
ducts. It surrounds the neck of the bladder and the beginning of the
urethra and is next to the rectum, through which an examination may be
made to determine its size. For it often enlarges in elderly men, the
frequent passage of urine in small amounts being a symptom of enlarged
prostate.

The _procreating glands_, which secrete the spermatozoa or semen, are
two in number, the _testes_ or _testicles_, and are homologous to the
ovaries in the female. They are ovoid in form and are suspended by the
_spermatic cords_ in a sac, the _scrotum_, back of the penis. During
early fetal life they are in the back of the abdomen near the kidneys,
but before birth they descend along the inguinal canals into the
scrotum. The excretory duct of the testis is called the _vas deferens_.
It passes up by the spermatic cord through the inguinal canal into
the pelvis to the base of the bladder and at the base of the prostate
joins the duct of the vesicula seminalis to form the _ejaculatory
duct_. The two _vesiculæ seminales_ are small receptacles for the semen
lying in contact with the base of the bladder and secrete a fluid with
which they dilute the semen. The ejaculatory duct terminates near
the prostate in the urethra by a slit-like orifice on each side, the
spermatozoa being finally excreted through the urethra.

The _penis_ is the external organ of generation in the male and is
attached to the pubes and the anterior part of the ischium. It is
composed of erectile tissue and encloses the urethra, the _meatus
urinarius_ appearing at its end as a vertical slit. Toward the end the
skin of the penis is loose and is prolonged forward in what is known
as the _prepuce_ or _foreskin_. It is this that is clipped away in
circumcision.

=The Female Generative Organs.=--The female generative organs include
the ovaries, Fallopian tubes, uterus, vagina, and the external
genitalia or vulva.

The _ovaries_, which are homologous to the testes in the male, are
two flattened oval bodies, grayish pink in color, suspended from the
lateral or broad ligaments which fasten the uterus to the walls of the
pelvis. They are one and a quarter inches long, three-quarters of an
inch wide, and half an inch thick and are attached at the upper end to
one of the fimbriæ of the Fallopian tubes. They consist of numerous
_Graafian follicles_ embedded in a fibrous stroma, each follicle
containing an _ovum_ about ¹/₁₂₅ inch in diameter and just visible to
the naked eye. When a follicle ruptures and discharges an ovum, an
irregular yellow spot, the _corpus luteum_, appears at the point of
rupture. After ordinary menstruation it is known as the _false corpus
luteum_ and after conception as the _true_ one, this one being larger
and lasting longer.

[Illustration: FIG. 65.--View of the pelvis and its organs. (Savage.)
_B_, Bladder; _U_, uterus (drawn down by loop _e_); _F_, Fallopian
tubes; _O_, ovaries; _L_, round ligaments; _g_, ureter; _a_, ovarian
vessels, often prominent under their peritoneal covering; _R_, rectum;
_V_, vertebra.]

The _Fallopian tubes_ are the oviducts and convey the ova from the
ovaries to the uterus. They are four inches long and lie between the
layers of the broad ligaments, opening into the uterus by an orifice
the size of a bristle, while the end next to the ovary spreads
out trumpet-like and is edged with _fimbriæ_ as with a fringe, the
fimbriated extremity. There are three _coats_: a serous coat which is
continuous with the peritoneum, a muscular coat, and, within, a mucous
coat covered with cilia, continuous with the mucous membrane of the
uterus. One fimbria is attached to the ovary and as the ovum is given
off it finds its way into the tube and thence to the uterus.

[Illustration: FIG. 66.--Sagittal section of the female pelvis.
(Dickinson.)]

The _uterus_ is a pear-shaped organ, about three inches long, two
inches broad above, and one inch thick, situated in the pelvic cavity
between the rectum and the bladder. The wide part or _fundus_ is
above and the narrow neck or _cervix_ below, lying partly within the
vagina. The whole is held in place by ligaments. These include the
_broad ligaments_, which extend from the sides of the uterus to the
lateral walls of the pelvis, and the _round ligaments_, two muscular
cords, about four inches long, which pass out through the abdominal
ring into the inguinal canal and so to the mons veneris and labia, thus
corresponding to the spermatic cords in the male. The cavity of the
body of the uterus is small and flattened and opens into the cervix by
the _internal os uteri_, the _external os_ being at the opening of the
cervix into the vagina. There are three _coats_: a serous coat derived
from the peritoneum, a muscular coat of unstriped fibers which forms
the bulk of the whole organ, and a mucous coat covered with ciliated
epithelium.

The uterus is always enlarged during menstruation and is enormously
enlarged in pregnancy. It receives the fecundated ovum, retains and
supports it during the development of the fetus, and is the chief agent
of expulsion. In _tubal_ or _extra-uterine pregnancy_ the ovum becomes
attached in the tube instead of in the uterus, and develops there,
rupturing the tube and causing serious hemorrhage.

The passage from the cervix out of the body is the _vagina_, a
membranous canal, curved upward and backward to conform to the axis of
the pelvis, and attached above to the cervix. Ordinarily the sides are
in contact.

The _arteries_ of the internal organs of generation are the uterine
from the internal iliac and the ovarian from the aorta in the female,
the pudic branches of the internal iliac and the spermatic from the
aorta in the male. The _nerves_ are largely from the sympathetic system.

_Abscess formation_ occurs frequently in the tubes and _gonorrheal
infection_ may spread up the vagina and through the uterus to the
tubes, and even to the abdominal cavity itself. The tubes may also be
_tubercular_.

_Salpingectomy_ or removal of the tubes is the commonest operation
after that for appendicitis. _Cancer_ of the uterus may necessitate
_panhysterectomy_ or removal of the uterus and all its appendages.

[Illustration: FIG. 67.--Virginal vulva. (Modified from Tarnier.) 1,
labia majora; 2, fourchette; 3, labia minora; 4, glans clitoridis; 5,
meatus urinarius; 6, vestibule; 7, entrance to the vagina; 8, hymen;
9, orifice of Bartholin’s gland; 10, anterior commissure of labia
majora; 11, anus; 12, blind recess; 13, fossa navicularis; 14, body of
clitoris.]

The _external genitalia_ in the female, as in the male, are situated
over the pubic arch. They are known as the _vulva_ and include the
mons Veneris, the labia majora and minora, the vaginal orifice, the
clitoris, and the meatus urinarius.

The _mons Veneris_ is a rounded eminence composed of fatty tissue,
which surmounts the pubic bones and is covered with hair at puberty.
From it two prominent longitudinal folds of skin, covered with hair
on the outside, the _labia majora_, extend backward, forming the
lateral boundaries of the vulva. Within these labia again are two
thin cutaneous folds, the _labia minora_ or _nymphæ_, which run back
from the clitoris for about one and a half inches and enclose the
_vaginal orifice_. The _clitoris_ corresponds to the penis and is
just above the upper part of the labia minora. Between it and the
vagina is the _meatus urinarius_. The orifice of the vagina is partly
closed in the virgin by the _hymen_, a thin fold of mucous membrane,
which occasionally closes it completely, _imperforate hymen_. The
_fourchette_ is a small transverse fold of skin at the junction of the
labia minora posteriorly. Between the vagina and the rectum is the
_perineal body_, a somewhat triangular structure made up of many small
muscles. Its surface is known as the _perineum_. It is frequently torn
wholly or in part during childbirth and has to be sewed up.

CHAPTER XII.

THE UPPER EXTREMITIES.

The upper extremities include the shoulders, arms, forearms, wrists,
and hands and contain each thirty-two bones. The bones of the two
shoulders taken together are called the _shoulder girdle_ and consist
of the two clavicles or collar bones and the two scapulæ or shoulder
blades, which together make an almost complete girdle of the shoulders.

The =clavicle= is a long slender bone extending almost horizontally
from the sternum to the scapula and can be felt for its whole length
in the living. For the inner two-thirds it is convex anteriorly,
for the outer third concave. In woman it is generally less curved,
smoother, and more slender than in man, and as bone is rough when the
muscles attached are powerful, the right clavicle, being used more, is
generally rougher and thicker than the left. Among the muscles attached
are the large neck muscle, the _sterno-cleido-mastoid_, whose tendons
form the _presternal notch_, the _trapezius_, the _pectoralis major_,
and the _deltoid_.

Being slender and superficial the clavicle is most frequently _broken_
of any bone in the body, generally by indirect violence, as by falling
with the hand out, though old people in such a case are apt to get
_Colles’ fracture_ at the wrist. The bone generally gives way at the
juncture of the outer and middle thirds, with displacement of the
parts inward, so that the fracture is seldom compound. Since, however,
the main vessels of the upper arm, with their nerves, lie beneath the
clavicle, there is danger of their being punctured. Such serious injury
is guarded against by the presence of the _subclavius muscle_. The
clavicle is occasionally removed for _sarcoma_.

[Illustration: FIG. 68.--Bones of the upper extremity. (Toldt.)]

[Illustration: FIG. 69.--Left scapula, posterior surface (after Toldt).]

The =scapula= or =shoulder blade=, so called from its shape, is a
large, flat, triangular bone with a prominent ridge, the _spine_,
crossing its dorsum or posterior surface near its upper edge. It
extends from the second to the seventh rib, with its posterior margin
parallel to and about one inch from the dorsal vertebræ. The _head_,
in which is situated the _glenoid cavity_ for articulation with the
humerus or upper arm bone, is surrounded by a slight constriction,
the _neck_. Above it projects the _coracoid process_, so called from
its fancied resemblance to a crow’s beak. This can usually be felt
about one inch from the juncture of the outer and middle thirds of
the clavicle and from it arise the short head of the biceps and the
coraco-brachialis muscle. The _acromion process_ at the end of the
spine extends out beyond the glenoid cavity posteriorly and affords
attachment to the deltoid and trapezius muscles. It forms the summit
of the shoulder. Numerous other muscles are attached to the surface
of the scapula, the only parts which are truly subcutaneous being the
whole length of the spine and the acromion process, though the lower
angle and the coracoid process can generally be felt. The muscles bulge
so much that the spine in the living appears as a slight depression
extending back almost to the vertebræ. The large number of the muscles
on the shoulder and arm is due to the great flexibility and strength
required for the various uses to which the arms are put.

=Shoulder Muscles.=--The most important shoulder muscle is the
_deltoid_, a large triangular muscle, which surrounds and protects
the shoulder-joint and gives the shoulder its rounded form. It rises
from the outer third of the clavicle, from the acromion process, and
from the whole length of the spine of the scapula, and is inserted
by a tendon into a rough prominence on the middle of the outer side
of the humerus. It serves to raise the arm and to draw it somewhat
forward or back, according as the anterior or posterior fibers are
used. The _pectoralis major_ rises from the inner half of the clavicle,
the front of the sternum, and the cartilages of the true ribs and its
fibers converge to form a fan-shaped muscle, which is inserted by a
flat tendon into the edge of the bicipital groove on the humerus. It
draws the arm forward and inward and helps considerably in forced
inspiration. The _serratus magnus_ rises from the outer surface and
upper border of the eight upper ribs and from an aponeurosis covering
the upper intercostal spaces, and is inserted along the whole length of
the posterior border of the scapula. It carries the scapula forward and
is used in pushing.

The scapula is seldom _broken_ because it is quite movable and is
covered with large muscles and because it lies on the chest, which
serves as an elastic cushion. The acromion process is the part most
frequently broken and occasionally the neck is fractured. _Tumors_
occur and may necessitate the amputation of the whole upper extremity.

=The Humerus.=--The bone of the upper arm, the humerus, is the largest
bone in the upper extremity and articulates with the scapula above
and with the ulna and radius below. At its upper end are the _head_
and the _anatomical neck_, with the _greater tuberosity_ external to
and the _lesser tuberosity_ in front of them. The constriction of the
surgical neck is below the tuberosities, and extending from between
them downward and inward along the upper third of the bone is the
bicipital groove for the long head of the biceps. Though round above,
below the _shaft_ becomes flattened from before backward and curves
slightly forward, terminating in the internal and external _condyles_,
from the former of which the flexors and the round pronator arise and
from the latter the extensors and supinators. From the external condyle
also there projects in front the _radial head_ or _capitellum_ for
articulation with the radius. Internally to the capitellum in front and
in a corresponding position on the back of the bone are the trochlear
surfaces for articulation with the ulna, there being a depression in
front called the _coronoid fossa_ for the reception of the _coronoid
process_ of the ulna in flexion of the forearm, and another depression
behind, the _olecranon fossa_, to receive the tip of the olecranon
process during extension. On the lower half of the humerus at the back
is the spiral groove for the _musculo-spiral nerve_ and the _superior
profunda artery_, while the _ulnar nerve_ runs in a groove back of the
internal condyle.

The humerus is almost completely covered with muscles, the only
part that is subcutaneous being a small portion of the external and
internal condyles. The head can be felt under the muscles and the
greater tuberosity forms the point of the shoulder. When the arm is
at the side, the biceps appears at the front and inner side and the
brachialis anticus on either side below, while on the back of the arm,
with its largest swelling above, is the triceps.

[Illustration: FIG. 70.

FIG. 70.--Superficial muscles of shoulder and arm (from before): 1,
Pectoralis major; 2, deltoid; 3, biceps brachii; 4, brachialis anticus;
5, triceps; 6, pronator radii teres; 7, flexor carpi radialis; 8,
palmaris longus; 9, flexor carpi ulnaris; 10, supinator longus; 11,
extensor ossis metacarpi pollicis; 12, extensor brevis pollicis; 13,
flexor sublimis digitorum; 14, flexor longus pollicis; 15, flexor
profundus digitorum; 16, palmaris brevis; 17, abductor pollicis.
(Dorland’s Dictionary.)]

[Illustration: FIG. 71.

FIG. 71.--Superficial muscles of shoulder and arm (from behind): 1,
Trapezius; 2, deltoid; 3, rhomboideus major; 4, infraspinatus; 5,
teres minor; 6, teres major; 7, latissimus dorsi; 8, triceps; 9,
anconeus; 10, brachialis anticus; 11, supinator longus; 12, extensor
carpi radialis longior; 13, extensor carpi radialis brevior; 14,
extensor communis digitorum; 15, extensor carpi ulnaris; 16, flexor
carpi ulnaris; 17, extensor ossis metacarpi pollicis; 18, extensor
brevis pollicis; 19, tendon of extensor longus pollicis. (Dorland’s
Dictionary.)]

=Upper Arm Muscles.=--The _biceps_ is the most important arm muscle. It
rises by a short head from the coracoid process of the scapula and by
a long head from a tubercle on the upper margin of the glenoid cavity,
the tendon arching over the head of the humerus and descending in the
bicipital groove. It is inserted into the back of the tuberosity of
the radius and by a broad aponeurosis into the fascia of the forearm.
It flexes and supinates the forearm and renders the fascia tense. Its
inner border forms a guide in tying the _brachial artery_, as this
artery runs along its inner side.

The _brachialis anticus_ rises from the lower half of the outer and
inner surfaces of the humerus and is inserted into the coronoid process
of the ulna, thus covering and projecting the elbow-joint anteriorly.
It is a flexor of the forearm.

Another smaller muscle on the anterior arm, which also aids in flexion,
is the _coraco-brachialis_, which extends from the coracoid process of
the scapula to the middle of the inner surface of the humerus.

Extending the entire length of the posterior surface of the humerus
is the _triceps_, similar to the quadriceps extensor in the thigh and
direct antagonist to the biceps and brachialis anticus muscles. It
rises by a long head from below the glenoid fossa, by the external head
from the upper third of the posterior surface of the humerus, and by
the internal head from the middle and lower thirds of the posterior
surface. It is inserted in the olecranon process of the ulna and serves
to extend the forearm and arm.

The humerus is more often _fractured_ by muscular action than any
other bone. Usually the fracture occurs in the lower half of the
bone and sometimes the musculo-spiral nerve is involved. There is a
great tendency to non-union, probably due to interposition of soft
parts. Sometimes the break is across and down between the condyles,
_T-fracture_. Involvement of the elbow-joint is more serious than
fracture of the humerus alone. _Sarcoma_ of the humerus does occur and
may require the removal of the clavicle and scapula as well as of the
arm bone itself. In _amputation_ of the humerus in children a long skin
flap is left to allow for growth of the bone, as it is liable to grow
again.

=The Ulna.=--In the forearm there are two bones, the ulna and the
radius, of which the former is the longer. The ulna is on the inner
side of the forearm and its upper end forms the greater part of the
articulation with the humerus, as most of the articulation at the wrist
is formed by the radius and the inter-articular fibro-cartilage. The
head of the ulna is at the lower extremity of the bone and articulates
on the outer side with the radius and below with the triangular
fibro-cartilage. From its inner side projects the _styloid process_.
The olecranon process forms the upper extremity and presents anteriorly
an articular surface, the _greater sigmoid cavity_, for articulation
with the trochlea of the humerus, where it fits into the olecranon
fossa during extension. The same articulating surface also covers
the _coronoid process_, a smaller projection below and in front of
the olecranon, which fits into the coronoid fossa during flexion.
Continuous with the greater sigmoid cavity on the outer side is the
_lesser sigmoid cavity_ for articulation with the head of the radius.
Under the _triceps tendon_, which is inserted into the olecranon, is a
_bursa_ or sac of synovial membrane, such as occurs in parts where much
force is brought to bear.

=The Radius.=--The radius, or spoke of the wheel, is on the outer
side of the forearm and gets its name from the way it turns upon
the ulna in pronation. The _shaft_ is larger below than above and
is slightly curved longitudinally for greater strength. The upper
extremity or _head_ is small and has a slightly concave upper surface
for articulation with the radial head of the humerus. It articulates by
its sides with the lesser sigmoid cavity and is bound to the ulna by
the _orbicular ligament_, which runs over a smooth articular surface.
Below the head is the constriction of the _neck_ with the tuberosity
for the biceps tendon to the inner side below. The lower extremity is
large and forms the chief part of the wrist-joint, articulating with
the semilunar and scaphoid bones of the wrist. From the lower extremity
the strong conical _styloid process_ projects externally.

[Illustration: FIG. 72.--Bones of the right forearm in a position of
supination. (Toldt.)]

In the living the _olecranon process_ of the ulna is always felt at
the elbow and the posterior border of the ulna forms the prominent
ridge down the forearm, leading to the styloid process. The head of
the radius is felt just below the external condyle and often makes a
dimple in the muscles of the forearm. The rest of its upper half is
concealed with muscles, but the lower half is easily felt as there are
only tendons over it. The styloid process is felt externally. Normally
that of the radius is a little lower than that of the ulna, so that in
cases of fracture their relative position is of considerable importance
as showing the amount of deformity.

The two forearm bones are more frequently _broken_ together than
separately and generally by direct violence, the lower fragment being
usually drawn up by the action of the flexor and extensor muscles and
producing a swelling on the palmar surface of the forearm. Indirect
violence usually causes fracture of the radius only. In both cases, but
especially in fracture of both bones, there is a tendency for membrane
to get between the fragments, so the arm is put up in splints with the
hand midway between pronation and supination in order to separate the
bones as far as possible. Care must be taken not to have the bandage
too tight or gangrene of the fingers may result. In most fractures of
the arm it is put up bent, but in _fracture of the olecranon_ it is put
up fully extended, as the fragment is sure otherwise to be displaced by
the pull of the triceps. In fact, the olecranon is sometimes fractured
by the muscular force of the triceps, though usually its fracture,
which is frequent, is due to direct violence. The ulna is also often
fractured in the middle by direct violence or the styloid process may
be broken. Fracture of the neck or shaft of the radius is very common,
the most important arm fracture being that of the lower end of the
radius or _Colles’ fracture_. This and the corresponding fracture in
the leg, _Pott’s fracture_, are two of the commonest fractures. In
_dislocation of the wrist_ the normal relation of the two styloid
processes remains unchanged, but in Colles’ fracture the lower fragment
often projects on the back of the hand, making a typical deformity
called the _silver fork deformity_.

The bones of the wrist and hand had best be described before the
forearm muscles are taken up, as the muscles of the forearm are
distributed largely to the fingers.

=The Wrist.=--The wrist or _carpus_ is made up of eight bones arranged
in two rows of four each. In the first row are the _scaphoid_ and
_semilunar bones_, on the outer side, articulating with the radius, the
_cuneiform_ articulating with the fibro-cartilage of the wrist-joint,
and the _pisiform_. In the second row, in corresponding positions,
are the _trapezium_, _trapezoid_, _os magnum_, and _unciform_. The
eminence felt on the radial side of the wrist is the protuberance of
the scaphoid, while the pisiform is generally felt on the ulnar side.

[Illustration: FIG. 73.--Right carpal bones, dorsal surface. _T_,
trapezium; _T´_, trapezoid; _7_, os magnum; _U_, unciform; _S_,
scaphoid; _L_, semilunar; _C_, cuneiform; _P_, pisiform.]

=The Hand.=--The hand contains nineteen bones, five _metacarpal bones_,
one for each finger and the thumb, whose bases articulate with the
lower row of wrist bones, and fourteen _phalanges_, three for each
finger and two for the thumb, of which the first row articulate with
the metacarpal bones. They are all long bones and are slightly concave
anteriorly. When the hand is flexed it is the heads of the metacarpal
bones, not the bases of the phalanges, that are so prominent, the head
of the third metacarpal being most prominent.

The metacarpals are seldom _fractured_, though bad fractures
occasionally occur. In comminuted fracture nothing can be done but
remove the bone. If the periosteum is left the bone will grow again.
Two diseases sometimes affect the metacarpals and the phalanges,
_tuberculosis_ and _syphilis_. Both cause swelling of the bones.

=Muscles of the Forearm.=--The chief groups of muscles on the forearm
are the _flexors_ and _pronators_ on the anterior surface and the
_extensors_ and _supinators_ on the posterior surface. In general the
flexors and pronators take their origin from on or around the internal
condyle, while the extensors and supinators arise on or around the
external condyle. Where not otherwise stated it will be understood that
such is their origin. In a general way they may by grouped as follows:

ANTERIOR SURFACE.
{ flexor carpi radialis
Flexors of wrist { flexor carpi ulnaris
{ palmaris longus

Flexors of fingers { flexor sublimis digitorum
{ flexor profundus digitorum

Flexor of thumb flexor longus pollicis

Pronators of hand { pronator radii teres
{ pronator quadratus

POSTERIOR SURFACE.
Extensor of forearm anconeus

{ extensor carpi radialis longior
Extensors of wrist { extensor carpi radialis brevior
{ extensor carpi ulnaris

{ extensor ossis metacarpi pollicis
Extensors of thumb { extensor primi internodii pollicis
{ extensor secundi internodii pollicis

Extensor of fingers extensor communis digitorum

Extensor of index finger extensor indicis

Extensor of little finger extensor minimi digiti

Supinators of hand { supinator longus
{ supinator brevis

Of the _flexors of the wrist_ the _flexor carpi radialis_ is inserted
into the base of the index and usually of the third metacarpal bone,
the _flexor carpi ulnaris_ into the fifth metacarpal, the pisiform and
the unciform bones, while the _palmaris longus_ goes to the anterior
annular ligament of the wrist and the palmar fascia of the hand. The
_flexor sublimis digitorum_ is inserted by four tendons into the second
phalanges of the fingers, while the _flexor profundus digitorum_ arises
from the upper part of the ulna and is inserted into the last phalanges
of the fingers. The _flexor of the thumb_ arises from the middle of the
radius and is inserted into the last phalanx of the thumb. Which joint
is flexed by a muscle depends upon the origin and insertion of the
muscle, all those included between being affected. Thus, the _flexor
sublimis digitorum_, which has its origin in part at least from the
condyle and is inserted in the second phalanges of the fingers, flexes
the forearm, wrist, and all the finger-joints but the last, while the
_flexor profundus digitorum_, arising from the ulna, though it flexes
the wrist and fingers, has no power of flexing the forearm.

The _pronator radii teres_, besides arising from the supra-condylar
ridge, rises from the coronoid process of the ulna. It is inserted into
the middle of the outer surface of the radius and serves to pronate
the forearm. The other pronator, the _pronator quadratus_, is a small
quadrilateral muscle extending transversely across the radius and ulna
just above their carpal extremities. It rises from the anterior surface
of the ulna and is inserted into the anterior external border of the
radius.

On the back of the forearm the _anconeus_ serves to extend the forearm
only, being inserted into the upper part of the posterior surface of
the ulna. The _extensors of the wrist_ are inserted into the bases of
the various metacarpal bones and have some power to extend the forearm
as well as the wrist. The _extensors of the thumb_, as their names
imply, go one to the metacarpal bone and one to each of the phalanges,
the longest one extending the whole thumb, the others only a part. They
rise from the ulna and radius, not the condyle. The _extensor communis
digitorum_ goes to all the phalanges of all the fingers, the _extensor
minimi digiti_ to those of the little finger only, and the _extensor
indicis_ to those of the index finger, the last two arising short of
the condyle.

Of the _supinators_ the longer one is inserted into the styloid process
of the radius, while the shorter one, the _supinator brevis_, is
inserted into the upper part of the same bone, both thus serving to
turn the radius on the ulna.

Where the _tendons_ of the various muscles pass over the wrist, both
front and back, they are covered with a synovial sheath and are held
down by a broad ligament, which some of them perforate, the annular
ligament. The strong fibrous band of the _anterior annular ligament_
arches over the carpal bones in front. Beneath it pass the median nerve
and the tendons of the flexors of the fingers and thumb. The _posterior
annular ligament_ is of less importance.

The deep _palmar fascia_ forms a sheath for the muscles of the hand.
In carpenters there sometimes occurs _Dupuytren’s contraction_ of the
palmar fascia, which draws the fingers up. As operation is not always
successful, it is quite a serious matter.

The _muscles of the hand_ itself include various abductor, adductor,
and short flexor muscles of the thumb and little finger. There also
extend between the metacarpal bones the _lumbricales_, four small
muscles that aid the deep flexor muscles; likewise seven _interossei_,
of which four are dorsal and three palmar. The _dorsal interossei_
arise by two heads from the adjacent sides of the metacarpal bones and
are inserted into the bases of the first phalanges, thus abducting the
fingers; while the _palmar interossei_, arising from the palmar surface
of the second, fourth, and fifth metacarpals, are inserted into the
three corresponding first phalanges and adduct the fingers toward an
imaginary line drawn through the middle finger.

=Joints of the Upper Extremity.=--The joints of the upper extremity,
with the exception of the wrist-joint, are the most freely movable of
any in the body, probably because the hand has the finest work to do
and a greater number of motions are required. Even the wrist has much
greater freedom of motion than the corresponding joint in the lower
extremity.

The _shoulder-joint_ is rather a deep joint, to allow of the varied
motion required, and has a capsular ligament from the margin of the
glenoid fossa above to the neck of the humerus below. The _elbow_,
which is a hinge joint, has an anterior and a posterior ligament and
two lateral ligaments, as is practically the case in all such joints.
The _wrist_ has several ligaments which, taken together, are capsular
in nature.

=Blood Supply of the Upper Extremity.=--The blood supply of the upper
extremity comes through the _subclavian artery_, which, on the right,
springs from the innominate artery and on the left from the aortic
arch. It remains one trunk as far as the elbow, though different names
have been given to different parts. Thus, as it passes over the lower
border of the first rib, it becomes the _axillary_, and at the lower
border of the axilla, where it starts down the arm, the _brachial_. At
the elbow it divides into the _ulnar_ and _radial arteries_.

In its upper part the _brachial artery_ lies internal to the humerus
but below it is in front of the bone. The _radial_ runs in a line from
the middle of the elbow anteriorly to the inner side of the styloid
process of the radius and is much exposed to injury in the lower third
of its course, as when the hand is thrust through glass. On it at the
wrist the pulse is counted. It is much smaller than the ulnar and winds
around the outer side of the thumb to the palm, where, with the deep
branch from the ulnar, it forms the _deep palmar arch_. The _ulnar
artery_ passes obliquely inward to the middle of the forearm and thence
along its ulnar border to the palm of the hand, where it divides into
the deep branch and the _superficial palmar arch_ which supplies the
four _digital arteries_.

From the _axillary artery_ branches go to the chest wall and shoulder,
the most important being the two _circumflex arteries_ to the deltoid.
The brachial has only two branches of any importance, the _superior_
and _inferior profunda_, both on the upper arm, of course.

In case of _hemorrhage_ compression can frequently be applied with the
fingers where the subclavian crosses the rib or in the axilla, where
the artery can be pressed up against the humerus.

=Nerves.=--The nerve supply of the shoulder comes chiefly from the
anterior and posterior _thoracic_, the _suprascapular_, and the
_circumflex_, these last going to the deltoid. The biceps is supplied
by the _musculo-cutaneous_, the triceps by the _musculo-spiral_, and
the brachialis anticus by both. Most of the flexor and pronator muscles
are supplied by the _median_, while the _posterior interosseous_ and
the _musculo-spiral nerves_ go to the extensors and supinators. The
_ulnar nerve_ supplies the hand largely.

CHAPTER XIII.

THE LOWER EXTREMITIES.

The lower extremities resemble the upper very closely in the
arrangement of the bones, muscles, arteries, and nerves, though
modifications occur, due to the difference in function of the lower
limbs. There is one long bone in the upper part or thigh, the femur,
and two in the lower part or leg, the tibia and fibula, while over the
knee-joint is the patella or knee-cap. The ankle has seven bones and
the foot nineteen like the hand.

=The Femur.=--The femur is the longest bone in the body, being about
one-fourth the height of the person. It inclines toward its fellow at
the knee in order to bring the knee-joints near the center of gravity
in walking, the amount of inclination varying with the width of the
hips and the height of the person. On account of the greater width of
hip the tendency to knock-knee is greater in women than in men.

The _shaft_ of the femur is enlarged at the extremities and is
slightly curved forward, the concavity being strengthened at the back
by a longitudinal ridge, the _linea aspera_, along part of which the
gluteus maximus muscle is attached. The _head_, which is covered with
cartilage, except for an oval depression for the attachment of the
ligamentum teres, one of the ligaments of the hip-joint, and which
articulates with the hollow of the acetabulum in the os innominatum,
projects considerably upward, inward, and forward from the shaft,
the _neck_ varying much in length and angle. It is generally more
horizontal in women than in men and in rickets the great weight on
the softened bone tends to press the head down, causing the deformity
known as “_coxa vera_”, in which the neck is almost horizontal.
Extending upward, outward, and backward from the shaft at the base
of the neck, about three-quarters of an inch lower than the head and
about on a level with the acetabulum and the spine of the os pubis,
is the _greater trochanter_. This large, irregular prominence and the
smaller one of the _lesser trochanter_, which is at the lower part of
the base of the neck posteriorly, are for the attachment of muscles
and to assist in rotating the bone. The lower extremity of the femur
is larger than the upper and is flat from before backward. Between its
two large eminences, the external and internal _condyles_, is a smooth
depression in front, the _trochlear surface_, for articulation with the
patella. The external condyle is more prominent in front, the internal
inferiorly, the latter being the longer of the two by about half an
inch. The _epiphysis_ at the lower end of the femur is the only one in
which ossification has begun at birth. Therefore, if ossification is
found there, the child is known to have arrived at full term.

[Illustration: FIG. 74.--Bones of the lower extremity. (Toldt.)]

So many large muscles are attached to the femur that the shaft cannot
be detected in the living unless the person is very thin and poorly
developed. The outer surface of the greater trochanter, however, and
the condyles can be felt.

A string stretched from the anterior superior spine of the ilium to the
tuberosity of the ischium passes in the middle just over the upper edge
of the greater trochanter. The line thus drawn is known as _Nélaton’s
line_ and is of considerable importance in many conditions of the
hip. Thus, if the hip is dislocated, the trochanter will be thrown
above _Nélaton’s line_, and in osteomalacia the pelvis sinks and the
trochanter is again above the line.

=Thigh Muscles.=--Of the thigh muscles only a few need be mentioned.
One large muscle is the _psoas magnus_, which has its origin on the
front of the last dorsal and all the lumbar vertebræ, passes down
across the brim of the pelvis and under Poupart’s ligament, gradually
diminishing in size, and terminates in a tendon that is inserted into
the lesser trochanter. It serves to flex the thigh on the pelvis and to
rotate it outward. The _psoas parvus_ rises from the last dorsal and
the first lumbar vertebræ and does not go out of the pelvis.

The _sartorius_ or _tailor muscle_ is flat and ribbon-like and is the
longest muscle in the body. It rises from the anterior superior spine
of the ilium and is inserted into the upper inner surface of the shaft
of the tibia. By it the legs are crossed. It also forms the outer side
of an important landmark, _Scarpa’s triangle_, whose base is formed by
Poupart’s ligament and the inner side by the _adductor magnus muscle_,
which passes from the ramus of the os pubis and the tuberosity of the
ischium to the linea aspera. The _femoral artery_ bisects the triangle
and runs into its apex.

The bulk of the anterior portion of the thigh is formed by the
_quadriceps extensor_, which is really made up of four muscles, the
_rectus femoris_, whose origin is on the anterior inferior iliac spine
and above the acetabulum; the _vastus externus_, which comes from
the greater trochanter and the upper linea aspera; and the _vastus
internus_ and _crureus_, which rise from the neck of the femur and
the linea aspera. It is inserted into the tubercle of the tibia by
the _ligamentum patellæ_, in which the patella lies. Its action is to
extend the leg.

At the back and forming the _buttocks_ are the three glutei muscles,
the _gluteus maximus_, _medius_, and _minimus_. All these rise from the
outer side of the ilium and have their insertion on or about the great
trochanter. They serve to hold the trunk erect and to extend, abduct,
and rotate the thigh.

[Illustration: FIG. 75.]

[Illustration: FIG. 76.]

[Illustration: FIG. 77.

FIG. 75.--Superficial muscles of hip and thigh (from behind): 1,
Gluteus medius; 2, gluteus maximus; 3, vastus externus; 4, biceps
flexor cruris; 5, semitendinosus; 6, semimembranosus; 7, gracilis; 8,
sartorius; 9, adductor magnus; 10, 11, gastrocnemius; 12, origin of
plantaris. (Dorland’s Dictionary.)

FIG. 76.--Muscles of the inner side of thigh and interior of pelvis:
1, Iliacus; 2, psoas magnus; 3, obturator internus; 4, pyriformis; 5,
erector spinæ; 6, gluteus maximus; 7, sartorius; 8, adductor longus; 9,
gracilis; 10, adductor magnus; 11, semimembranosus; 12, semitendinosus;
13, rectus femoris; 14, vastus internus. (Dorland’s Dictionary.)

FIG. 77.--Superficial muscles of front of thigh: 1, Insertion of
external oblique into iliac crest; 2, aponeurosis of external oblique;
3, external abdominal ring; 4, gluteus medius; 5, tensor vaginæ
formoris; 6, sartorius; 7, iliopsoas; 8, pectineus; 9, adductor longus;
10, gracilis; 11, adductor magnus; 12, vastus externus; 13, rectus
femoris; 14, vastus internus; 15, biceps flexor cruris. (Dorland’s
Dictionary.)]

Lower down and forming the back of the thigh are the biceps and the
semitendinosus and semimembranosus muscles. The _biceps_ rises by two
heads from the tuberosity of the ischium and the linea aspera and is
inserted into the head of the fibula. It is on the outer side of the
thigh and its tendon, which embraces the external lateral ligament of
the knee-joint, forms the _outer hamstring_. On the inner side are the
_semitendinosus_ and the _semimembranosus muscles_. These rise from
the tuberosity of the ischium and are inserted, the one into the upper
inner surface of the shaft of the tibia and the other into the internal
tuberosity of the tibia. Their tendons form the _inner hamstring_.
Like the biceps they serve to extend the thigh and flex the leg on the
thigh, but where the biceps rotates the leg out they, being attached to
the inner side of the leg bones, rotate it in.

=The patella=, or _small pan_, is a flat, somewhat triangular bone
developed in the quadriceps extensor tendon. Four _muscles_ are
attached to it as well as the ligamentum patellæ, which holds it to the
tibia and gives increased leverage by making the quadriceps extensor
work at a greater angle. It articulates with the condyles and serves
to protect the joint. One bursa, the _prepatella bursa_, separates it
from the skin and another, surrounded by adipose tissue, from the head
of the tibia. The external surface can be seen and felt on the front of
the knee and the bone can be moved from side to side when the leg is
straight.

=Joints of the Lower Extremity.=--The _hip-joint_ is a ball-and-socket
joint but is not so freely movable as the shoulder-joint, the head of
the femur being held in the acetabulum by many strong ligaments, of
which the most important is the _capsular_ ligament.

The _knee-joint_ is largely a hinge joint, but in some positions it has
some rotation. It is formed by the condyles of the femur, the head of
the tibia, and the patella, and has fourteen ligaments, including the
_ligamentum patellæ_ and the _crucial ligaments_. Its synovial sac is
the largest found in any joint. Two _semilunar cartilages_, placed on
the head of the tibia, serve to deepen the socket for the condyles,
changing somewhat in shape and thickness as the joint moves. The
interval between the thigh and the leg bones can be felt at the knee.
When the leg is extended the juncture of the bones is slightly above
the patella, while in flexion a knife passed below the apex of the
patella will pass into the joint.

_Congenital dislocation_ of the hip occurs. _Separation of the
epiphysis of the femur_ may occur and sometimes the neck, rarely
the lower part of the shaft, is _fractured_. Either condyle may
be fractured off or there may be a T-fracture, in which case the
popliteal artery may be injured. In _dislocation_ the head may be
behind or in front of the acetabulum. _Impacted hip_, where the neck
of the femur has, in a fall, been driven into the head, is common
in old people. Sometimes, especially in young children, the bone is
infected, _osteomyelitis_. _Sarcoma_ occurs. Most tubercular disease of
the hip originates at the upper extremity of the femur, _tuberculosis_
generally starting in the head and then attacking the capsule and
the soft parts of the joint. If neglected, shortening of the leg may
result, in which case the bone has to be broken and set at an angle in
order to enable the child to walk.

[Illustration: FIG. 78.]

[Illustration: FIG. 79.

FIG. 78.--Right knee-joint, posterior view. (Leidy.)

FIG. 79.--Right knee-joint, showing internal ligaments: 2, anterior
crucial ligament; 3, posterior crucial ligament; 4, transverse
ligament; 6, 7, semilunar fibro-cartilages. (Leidy.)]

Occasionally a bit of cartilage gets broken off in the knee-joint and
wedged between the bones, so that the joint cannot be straightened.
This is _dislocation of the semilunar cartilage_ and necessitates an
operation for removal of the piece. The cartilage will eventually
be replaced by fibrous tissue and in a few months the leg will be
all right. _Dislocation of the knee_ is rare, though it may occur
in any direction. Often the bursæ of the joint are irritated, as by
kneeling to scrub floors, and _bursitis_ or _housemaid’s knee_ results.
_Fracture of the patella_ may be caused by muscular traction or by
direct violence, and is generally repaired by making an incision
and sewing the parts of the bone together. _Tumor albus_ or _white
swelling_ is _tuberculosis of the knee_ and is fairly common in
children. _Specific knee_ means _syphilis of the knee_ and generally
occurs in both knees.

=The Tibia.=--The tibia or _shin bone_ is next longest to the femur
and is on the inner side of the leg, corresponding to the ulna in the
arm. The _shaft_ is prismoid and is more slender for the lower quarter,
where fracture is consequently most frequent. The anterior border forms
the _crest_ or shin and can be felt for its upper two-thirds. The
lower extremity, which is smaller than the upper, articulates with the
astragalus bone of the ankle and with the fibula. Its _head_ or upper
extremity is expanded into two lateral _tuberositis_ for articulation
with the femur and for muscular attachment, both of which can easily
be felt just below the bend of the knee. Their upper surfaces are
smooth and concave, with a vertical bifid spine in the middle and a
prominent tubercle for the attachment of the semilunar cartilages on
either side. On the anterior surface of the head, below, is a rough
eminence or tubercle, which also can be felt. The lower part of this
is for the attachment of the ligamentum patellæ, while the upper part,
which is smoother, is for the bursa that is placed under the tendon to
prevent friction. On the back of the outer tuberosity is a facet for
the head of the fibula. At the lower end there projects downward on the
inner side, overhanging the arch of the foot, the _internal malleolus_,
the prominent part of the ankle. It is on a higher level and somewhat
farther forward than the _external malleolus_.

=The Fibula.=--The fibula is the most slender of all the bones in
proportion to its length and is on the outer side of the leg. Its
_head_ is small and placed toward the back of the tibia below the
knee-joint, from which it is excluded. The head articulates with the
external tuberosity and has extending upward from it the styloid
process. To it is attached the _biceps tendon_ or _outer hamstring_.
At the lower extremity of the shaft is the _external malleolus_, which
articulates with the astragalus and forms the outer ankle. The only
parts of the fibula that can be felt, besides the malleolus, which is
very prominent, are the head and the lower external surface of the
shaft.

In _fracture of the leg_ both bones are usually broken, though either
may be broken separately. _Pott’s fracture_ is fracture of the lower
fibula, and may be caused by stamping hard when stepping on to the
sidewalk. In rickets the tibia becomes bowed outward and forward,
causing _bow leg_, a condition which in very young children may be
rectified by manipulation. Later on braces are needed and after five
years the bones have to be broken and set straight.

=The Ankle.=--The ankle or _tarsus_ has but seven bones where the
wrist has eight. They are the _os calcis_ or _heel bone_, which is
the largest and strongest and forms the tuberosity of the heel; the
_astragalus_, which is next largest and helps to form the ankle-joint;
the _cuboid_; the _navicular_ (_boat-like_) or _scaphoid_; and the
internal, middle, and external _cuneiform bones_. The astragalus is
above and partially in front of the os calcis, to which is attached
the _tendo Achillis_. The _cuboid_ is on the outer side of the foot,
in front of the os calcis and behind the metatarsals. It is noticeable
in _congenital club-foot_, in which condition the tarsal bones may be
distorted in shape and misplaced. The _navicular_ or _scaphoid_ is
on the inner side of the foot, between the astragalus and the three
cuneiform bones.

=The Foot.=--There are five _metatarsal bones_ in the foot,
corresponding to the five metacarpals in the hand, and the toes have
the same number of _phalanges_ as the fingers, though they are shorter
and stronger. The big toe corresponds to the thumb.

[Illustration: FIG. 80.--Bones of the right foot, dorsal surface:
1, Astragalus; 2, talus; 3, os calcis, 4, navicular; 5, internal
cuneiform; 6, middle cuneiform; 7, external cuneiform; 8, cuboid; 9,
metatarsus; 10-14, phalanges. (Leidy.)]

_Fracture_ of the os calcis and the astragalus are most commonly caused
by a fall from a height, while the metatarsals and phalanges are
generally broken by something heavy falling upon them. Because of their
delicate structure, their distance from the heart, and the differences
of temperature to which they are subjected, the tarsal bones are
especially liable to become _tubercular_, amputation of the feet even
becoming necessary at times. In diabetes there may be a perforating
ulcer on the sole of the foot and the bone may become diseased.

[Illustration: FIG. 81.]

[Illustration: FIG. 82.]

[Illustration: FIG. 83.

FIG. 81.--Superficial muscles of the leg from inner side: 1,
Vastus internus; 2, sartorius; 3, gracilis; 4, semitendinosus; 5,
semimembranosus; 6, inner head of gastrocnemius; 7, soleus; 8, tendon
of plantaris; 9, tendon of tibialis posticus; 10, flexor longus
digitorum; 11, flexor longus hallucis; 12, tibialis anticus; 13,
abductor hallucis. (Dorland’s Dictionary.)

FIG. 82.--Muscles of leg and foot (from before): 1, Tendon of rectus
femoris; 2, vastus internus; 3, vastus externus; 4, sartorius; 5,
iliotibial band; 6, inner head of gastrocnemius; 7, inner part of
soleus; 8, tibialis anticus; 9, extensor proprius hallucis; 10,
extensor longus digitorum; 11, peroneus longus; 12, peroneus brevis;
13, peroneus tertius; 14, origin of extensor brevis digitorum.
(Dorland’s Dictionary.)

FIG. 83.--Superficial muscles of leg (from behind): 1, Vastus externus;
2, biceps flexor cruris; 3, semitendinosus; 4, semimembranosus; 5,
gracilis; 6, sartorius; 7, outer, and 8, inner, head of gastrocnemius;
9, plantaris; 10, soleus; 11, peroneus longus; 12, peroneus brevis; 13,
flexor longus digitorum; 14, tibialis posticus; 15, lower fibers of
flexor longus hallucis. (Dorland’s Dictionary.)]

=Muscles of the Leg.=--The greater part of the calf of the leg is
formed by the _gastrocnemius_, a large bulging muscle, which rises from
the condyles of the femur and is inserted along with the _soleus_,
whose origin is on the back of the upper fibula, and the _plantaris_,
which comes from the linea aspera, into the os calcis by a common
tendon, the _tendo Achillis_, the largest and strongest tendon in
the body. Its action is to extend the foot and to rotate it slightly
inward. Other extensors of the foot, which also evert it, are the
_peroneus longus_ and the _peroneus brevis_ at the upper and outer part
of the leg, the former rising from the outer tuberosity of the tibia
and the upper fibula and being inserted into the first metatarsal and
the internal cuneiform, the latter arising from the lower fibula and
being inserted into the fifth metatarsal. The foot is flexed, adducted,
and rotated inward by means of the _tibialis anticus_, which rises from
the outer tuberosity and the upper two-thirds of the outer surface of
the tibia and is inserted into the internal cuneiform bone.

In the foot, and corresponding to the palmar fascia in the hand, is
the _plantar fascia_, the densest of all fibrous membranes. There are
also various annular ligaments, and the _foot muscles_ are arranged
similarly to those in the hand.

=The Blood Supply of the Lower Extremity.=--The blood supply of the
lower extremity comes from the _external iliac artery_, a branch of the
_common iliac_, which passes obliquely downward and outward along the
border of the psoas muscle to Poupart’s ligament, where it enters the
thigh and becomes the _femoral artery_. Its only important branches are
the _deep epigastric_, which goes up along the internal abdominal ring,
and the _deep circumflex iliac_. As the _femoral artery_ it passes
down the inner side of the thigh to the internal condyle of the femur,
being very superficial at Scarpa’s triangle, where it can be compressed
with the thumb to stop hemorrhage below. If a tourniquet is applied,
it should be applied a little lower down. The first and most important
branch of the femoral is the _profunda femoris_.

About two-thirds of the way to the knee the artery takes the name
_popliteal_. It lies superficially in the popliteal space back of the
knee, but above and below it is covered with muscles. Its branches
supply the knee-joint and nearby muscles and are unimportant. At the
lower border of the _popliteus muscle_, a small muscle at the knee, it
divides into the _anterior and posterior tibial arteries_. The course
of the former of these may be marked by a line from the inner side of
the head of the fibula to midway between the malleoli at the front of
the ankle, where it terminates in the _dorsalis pedis artery_ for the
back of the foot. By this last the pulse is sometimes taken and its
pulsation is a guide in determining how high up to amputate in gangrene
of the foot. The posterior tibial extends obliquely down the back of
the leg to the heel, where it divides into the _internal and external
plantar arteries_ which go to the sole of the foot. Its most important
branch is the _peroneal_.

Besides the _deep veins_ accompanying the arteries there are the
_superficial veins_, the _internal_ or _long saphenous_ on the inner
side of the leg and thigh and the _external_ or _short saphenous_ on
the middle of the leg posteriorly and emptying into the popliteal vein.
Varicosity often occurs in these veins.

=Nerves.=--The nerves of the muscles about the hip are branches of the
_lumbar nerve_. The _anterior crural_ supplies the anterior part of
the thigh, the _gluteal_ the muscles of the same name, and the _great
sciatic_ the large muscles of the back of the thigh. Below the knee
the _anterior tibial_ goes to the tibialis anticus and the _internal
popliteal_ to the muscles of the calf, while the peroneus muscles are
supplied by the _musculo-cutaneous_.

INDEX.

Abdomen, 132
muscles, 132, _et seq._
nerves, 134
regions, 134, 135
contents, 135, 136
Abdominal aorta, 107, 109
Abducens nerve, 83
Abscess, 34, 51, 52, 100, 137, 152, 159, 168
Absorbent vessels or lymphatics, 34
Absorption of food, 33
in intestines, 144
in mouth, 136
in stomach, 140
Accommodation of eye, 72
Acetabulum, 162, 187
Acromion process, 173
Adam’s apple, 121
Adductor magnus muscle, 190
Adenoids, 62
Adipose tissue, 16
Air, changes by breathing, 129, 130
complemental, 129
residual, 129
supplemental, 129
tidal, 129
Air cells, 27
Albumin in urine, 158
Albuminoids, 12
Alimentary canal, 136, _et seq._
Alveoli of lungs, 126
Amœba, 12
Ampullæ of mamma or breast, 100
Amputation, 177
Amylopsin, 144
Anabolism, 147
Anasarca, 152
Anatomy, 11
Anconeus muscle, 182, 183
Anemia, 120
Aneurism, 109
Ankle, 195
Annular ligaments, 184, 198
Ano-spinal reflex, 146
Antrum of Highmore, 54, 57
Anus, 141, 146
Aorta, 99, 107, 109
Aortic valve, 104
Aponeuroses, 23
Apoplexy, 79, 118
Appendages of the skin, 40
Appendix, vermiform, 145
Aqueous humor, 70
Arachnoid, 76
Areola, 100
Areolar tissue, 15
Arteries, 27, 28, 29, 107
nerves, 29
of back, 94, 95
of brain, 77
of breast, 100
of chest, 99
of heart, 107
of intestine, 143, 145
of kidney, 156
of lower extremity, 198, 199
of organs of generation, 168
of pancreas, 153
of spleen, 153
of stomach, 139
of upper extremity, 185, 186
structure, 27
Artery, axillary, 99, 100, 108, 185
basilar, 77, 108
brachial, 108, 177, 185
carotid, common, 107, 108
internal and external, 108, 137
celiac axis, 109, 143, 150, 153
cerebral, 77
circumflex, 186
coronary, 107
communicating, 78
digital, 186
dorsalis pedis, 199
epigastric, deep, 198
facial, 28
femoral, 190, 198
gastric, 109
hepatic, 109, 150
iliac, common, 107, 109
internal and external, 95, 109, 198
circumflex, 198
innominate, 107
intercostal, 95, 97, 100, 108
lumbar, 95, 109
mammary, internal, 99, 100, 108
mediastinal, 99
mesenteric, 109, 143, 145, 153
ophthalmic, 70
peroneal, 199
phrenic, 99, 109
plantar, internal and external, 199
popliteal, 198
profunda, superior and inferior, 175, 186
femoris, 198
pudic, 168
pulmonary, 106, 110
radial, 108, 185
renal, 109
spermatic or ovarian, 109, 168
splenic, 109, 153
subclavian, 94, 99, 107, 108, 185
suprarenal, 109
suprascapular, 94
thyroid axis, 108
tibial, 198
transversalis colli, 94
ulnar, 108, 185
umbilical, 107
uterine, 168
vertebral, 77
Arytenoid cartilages, 122
Ascending aorta, 107
colon, 145
Ascites, 34, 152
Asphyxia, 128
Astigmatism, 73
Astragalus, 195
Atlas, 91
Auditory meatus, 52
canal, external, 63
internal, 64
center, 81
nerve, 64, 65, 84
Auricles of heart, 103
Axilla, 32
Axillary artery, 99, 100, 108, 185
Axis, 91
Axis-cylinder process, 36, 37

Back, 88, _et seq._
muscles, 93, 94
arteries, 94, 95
nerves, 95
Basilar artery, 77, 108
Basilic vein, 109
Biceps of arm, 175, 176
of leg, 190, 191
Bicipital groove, 175
Bicuspid or mitral valve, 104
teeth, 60
Bile, 36, 143, 150
Bilirubin, 12, 143, 151
Biliverdin, 143, 151
Bladder, 160
Blind spot, 70
Blood, 27, 116, _et seq._
amount, 116
arterial and venous, 29
circulation of, 29, 105, _et seq._
coagulation, 117, 118
coloring matter, 119
composition, 116, 117
corpuscles, 116, 118, _et seq._
fibrin, 117
functions of, 116
plaques, 120
plasma, 33, 116, 117
pressure, 114, 115
serum, 117
vessels, 27, _et seq._
Bone, 17
astragalus, 195
atlas, 91
axis, 91
canaliculi, 17
cancellous or spongy, 17
carpal, 180, 181
chemical composition, 18
clavicle, 171
coccyx, 90, 161
compact, 17, 18
cuboid, 195
cuneiform, 181, 195
endosteum of, 18
ethmoid, 48, 53
femur, 187
fibula, 194, 195
formation of, 18
frontal, 49
Haversian canals of, 17
humerus, 175
hyoid, 60
ilium, 161, 162
incus, 63
innominate, 161, 162
ischium, 161, 163
lachrymal, 48, 54
lacunæ of, 17
lamellæ of, 17
malar, 48, 54
malleus, 63
marrow of, 18
maxillary, inferior, 48, 55
superior, 48, 54
metacarpal, 181
metatarsal, 195
nasal, 48, 55
navicular, 195
occipital, 48, 50
os calcis, 195
os innominatum, 161, 162
os magnum, 181
palate, 48, 54
parietal, 48, 49
patella, 19, 192
pelvis, 161
periosteum of, 18
phalanges, of foot, 195
of hand, 181
pisiform, 181
pubes, 161, 163
radius, 178, 179
ribs, 97, 98
sacrum, 90, 161
scaphoid, 181, 195
scapula, 173
semilunar, 181
sphenoid, 48, 52
stapes, 63
sternum, 97
structure of, 17
tarsal, 195
temporal, 48, 51
tibia, 194
trapezium, 181
trapezoid, 181
turbinated, 53
inferior, 48, 53, 54
ulna, 177, 178
unciform, 181
vertebræ, 88
vomer, 48, 55
Bones, classification of, 19
flat, 20
function of, 19, 20
long, 19
of back, 88
of chest, 97, 98
of cranium, 48, _et seq._
of face, 53, _et seq._
of lower extremity, 187, _et seq._
of upper extremity, 171, _et seq._
pelvic, 161, _et seq._
sesamoid, 19
short, 20
Wormian, 19, 49
Bow leg, 195
Brachial artery, 108, 177, 185
plexus, 84, 85
Brachialis anticus, 175, 177
Brain, 75, _et seq._
areas, 81, 82
arteries, 77
function, 80, _et seq._
parts, 75
Broad ligaments of uterus, 165, 166, 168
Bronchi, 123, 125
Buffy coat, 117
Bursæ, synovial, 20, 178
Bursitis, 194
Buttocks, 190

Canal, alimentary, 136, _et seq._
auditory, 63, 64
central, of cord, 81
Haversian, 17
semicircular, 64, 66
Canaliculi of bone, 17
Cancellous tissue of bone, 17
Cancer, 35, 58, 62, 100, 122, 139, 146, 169
Canine teeth, 60
Canthus of eye, 67, 68
Capillaries, 28, 29
Capitellum, 175
Capsular ligament of hip, 193
Carbohydrates, 12, 26, 147, 148, 151
Cardiac cycle, 104
muscle, 22, 25
nerve, 78
plexus, 87
Caries, 98
Carotids, common, 107, 108
internal and external, 108, 137
Carpal bones, 180, 181
Carpus or wrist, 180, 181
Cartilage, 16
Cartilages, arytenoid, 122
costal, 98
cricoid, 121
thyroid, 121
triangular, 57
Casein, 11
Cauda equina, 79, 91
Cecum, 145
Celiac axis, 109, 150, 153
Cells, 12, 13
Central canal of cord, 81
Cephalocele, 53
Cerebellum, 51, 78
Cerebral arteries, 77
veins, 78
Cerebro-spinal fluid, 34, 76, 79
meningitis, 79
nervous system, 75, _et seq._
Cerebrum or brain proper, 51, 75
Cervical nerves, 84
plexus, 84
vertebræ, 90, 91
Cervix of uterus, 168
Chemical composition of the body, 11
of bone, 18
Chest or thorax, 96
arteries, 99
bones, 97, 98
muscles, 98, 99
nerves, 99
Cholesterin, 143
Chordæ tendineæ, 104
Choroid, 68
Chromatic aberration, 73
Chyle, 32, 33, 144
Chyme, 139, 140
Cilia, 15, 27
Ciliary muscles, 69, 72
processes, 69, 72
Circle of Willis, 78, 108
Circulation of the blood, fetal, 106, 107
portal, 109, 110
pulmonary, 110
systemic, 105, 106, 107, _et seq._, 112, 113
Circumflex artery, 186
Circumflex nerve, 85, 186
Circumvallate papillæ, 61
Cirrhosis of liver, 152
Clavicle, 171
Cleft palate, 55
Clitoris, 170
Clotting of blood, 23, 117, 118
of lymph, 33
of muscle, 23
Club-foot, 195
Coccygeal nerve, 84
vertebræ, 90
Coccyx, 90, 161
Cochlea, 64, 65
Colles’ fracture, 171, 180
Color blindness, 73
perception, 73
Coloring matters, 12
of bile, 143, 151
of blood, 119
Colon, ascending, 145
descending, 145
transverse, 145
Columnæ carneæ, 104
Commissures of cord, 80
Common bile duct, 150
Communicating arteries, 78
Compact tissue of bone, 17, 18
Condyles, humerus, 175
femur, 189
Conjunctiva, 67
Conjugate focus, 71
Convolutions of brain, 76
Connective tissue, 15, _et seq._
areolar, 15
bony, 17
cartilaginous, 16
elastic, 15
fatty or adipose, 16
fibrous, 15
Coraco-brachialis, 177
Coracoid process of scapula, 173
Cordiform tendon, 98
Cornea, 27, 68, 70
Cornicula laryngis, 122
Coronary artery, 107
sinus, 105
valve, 105
Coronal suture, 48
Coronoid fossa, 175
process, 178
Corpus luteum, 166
Corpuscles of blood, 116, 118, _et seq._
tactile, 37, 39, 46
Corti, organ of, 65
Costal cartilages, 98
Coughing, 131
“Coxa vera,” 189
Cranial nerves, 77, 78, 83, 84
Craniotabes, 53
Cranium, bones of, 48, _et seq._
Cribriform plate of ethmoid bone, 53
Cricoid cartilage, 121
Crista galli, 53
Cross eye, 72
Crossed pyramidal tract, 82
Crucial ligaments, 193
Crural nerves, 85, 199
Crureus, 190
Crying, 131
Crypts of Lieberkühn, 143, 144, 145
Crystalline lens, 69, 70
Cuboid bone, 195
Cuneiform bones, ankle, 195
wrist, 181
cartilages, 122
Cutaneous nerves, 46, 85
Cystic duct, 143, 152

Deltoid, 174
Dendrites, 36
Derma, 39
Descending aorta, 107
colon, 145
Diabetes mellitus, 151, 196
Diaphragm, 98, 99, 128
Diaphysis, 18
Diastole, 104, 106
Differentiation of tissues, 13
Digestion, in mouth, 136
in small intestine, 143, 144
in stomach, 139, 140
of fats, 144
of proteids, 140, 144
of starch, 136, 144
Digital arteries, 186
Diphtheria, 35
Diploë, 20, 48
Direct cerebellar tract, 82
pyramidal tract, 80, 82
Dislocation, 180, 193, 194
Diuretics, 158
Dorsal or thoracic nerves, 84, 85
vertebræ, 90, 91
Dorsalis pedis artery, 199
Duct, common bile, 150
cystic, 143, 152
ejaculatory, 165
hepatic, 143, 150
lachrymal, 68
of Rivinus, 62
pancreatic, 153
right lymphatic, 31, 32
Stensen’s, 62
Wharton’s, 62
Ductless glands, 36
Ductus arteriosus, 106, 107
communis choledochus or common bile duct, 150
Duodenum, 142
Dupuytren’s contraction, 184
Dura mater, 15, 76, 79
Ear, 63, _et seq._
external, 63
function of, 65
internal, 64
function of, 65
middle, 63
function of, 65
Edema, 33, 34, 122
Eighth nerve, 64, 84
Ejaculatory duct, 165
Elbow, 32
joint, 185
Elastic tissue, 15
Eleventh nerve, 84
Emmetropic eye, 72
Emphysema, 97
Empyema of gall-bladder, 152, 153
of lungs, 126
End bulbs, 37
Endocardium, 103
Endolymph, 64, 65
Endosteum, 18
Endothelium, 14, 40
Ensiform cartilage, 97
Epidermis, 27, 39
Epigastric artery, 198
Epigastrium, 135
Epiglottis, 60, 121, 136
Epiphysis, 18, 189, 193
Epithelium, 14, 27
ciliated, 15, 27
columnar, 14
glandular, 14
pavement, 14
simple, 14
stratified, 14
Erythrocytes, 118, 119
Esophagus, 138
Ethmoid bone, 53
Eustachian tubes, 52, 63
valve, 106, 107
Excreting glands, 35
Extensor carpi radialis longior, 182, 183
brevior, 182, 183
ulnaris, 182, 183
communis digitorum, 182, 184
indicis, 182, 184
minimi digiti, 182, 184
ossis metacarpi pollicis, 182, 183
primi internodii pollicis, 182, 183
secundi internodii pollicis, 182, 183
Eye, 66, _et seq._
accommodation, 72
coats of, 68
color of, 69
formation of image in, 70, _et seq._
humors of, 70
muscles of, 67
nerves of, 67, 68
teeth, 60
Eyeball, 66
Eyebrows, 66
Eyelashes, 67
Eyelids, 66, 67

Face, bones of, 53, _et seq._
Facial artery, 28
nerve, 83, 84
Fallopian tubes, 166, 167
Far-sightedness, 72, 73
Fat or adipose tissue, 16
Fats, 12, 147, 148
absorption, 144
digestion, 143, 144
False pelvis, 163
ribs, 97
Fascia, lumbar, 133
Fascia, palmar, 184
plantar, 198
Fasciæ, 15, 21
Fasciculi, 21
Fauces, pillars of, 59
Feces, 146
Female generative organs, 163, 165, _et seq._
Femoral artery, 190, 198
Femur, 187
Fenestra ovalis, 63, 65
rotunda, 65
Ferments, 12, 136, 144
Fetal circulation, 106, 107
Fetus, 111
Fever, 45
Fibrin, 11, 23, 33, 117
ferment, 117
Fibrinogen, 117
Fibrous tissue, 15
Fibula, 194, 195
Fifth nerve, 83
Filum terminale, 78, 91
Fimbriæ, 167
First nerve, 83
Fissure of Rolando, 75, 82
of Sylvius, 75
Flexor carpi radialis, 182, 183
ulnaris, 182, 183
longus pollicis, 182, 183
profundus digitorum, 182, 183
sublimis digitorum, 182, 183
Floating ribs, 97
Follicles, Graafian, 166
Fontanelles, 19, 49
Food, 147
amount, 148
classes of, 147
cooking, 148
function, 147, 148
Foot, bones of, 195, 196
muscles of, 198
Foramen, intervertebral, 90
magnum, 50
nutrient, 19
obturator, 163
of Majendie, 79
optic, 66, 70
ovale, 106
Foreign bodies, 118, 122, 137, 146
Fossa, coronoid, 175
glenoid, 51
iliac, 163
nasal, 55, 57
olecranon, 175
Fourchette, 170
Fourth nerve, 68, 83
Fovea centralis, 70
Fractures, 98, 164, 171, 174, 175, 177, 180, 181, 193, 194, 195, 196
Frenum of tongue, 60
Frontal bone, 48, 49

Gall-bladder 143, 152, 153
stones, 143
Ganglia, 87, 110
Gangrene, 180, 199
Gastric artery, 109
glands, 35
juice, 139
vein, 110, 150
Gastrocnemius, 196
Generative organs, female, 163, 165, _et seq._
male, 163, 164, 165
Genito-crural nerve, 85
Gladiolus 97
Glands, 32, 35, 36
ductless, 36
excreting, 35
functions, 36
gastric, 35
lachrymal, 68
lymphatic, 32, 34, 35
mammary, 99, 100
Meibomian, 67
of Lieberkühn, 143, 144, 145
parotid, 51, 62
Peyer’s, 142
procreating, 165
prostate, 164, 165
racemose, 35
salivary, 35, 61, 136
sebaceous, 35, 40, 41
secreting, 35
solitary, 142, 145
sublingual, 56, 62
submaxillary, 56, 62
sweat, 35, 42
thymus, 124
thyroid, 124
Glenoid cavity, 173
fossa, 51
Globulin, 11
Glosso-pharyngeal nerve, 61, 84
Glottis, 122, 129
Gluteal nerves, 199
Glutei muscles, 190
Glycogen, 26, 36, 150, 151
Goiter, 124
Gonorrhea, 160, 168
Graafian follicles, 166
Gray matter of brain and cord, 36, 75, 76, 78, 80, 81
Green-stick fracture, 19
Groin, glands of, 32, 35
Gustatory cells, 61

Hair, 27, 40
follicle, 40
Hamstring, inner, 191
outer, 191
Hard palate, 55, 59
Haversian canals, 17
Hearing, sense of, 65
Heart, 101, _et seq._
beat, 102, 104, 111, 112
nerves, 110, 111
position, 102
sounds, 111
structure, 103, 104
Heat center, 45
production, 44
prostration, 45
stroke, 45
Hemoglobin, 119, 130
Hemorrhage, 139, 186
Hemorrhoidal veins, 146
Hemorrhoids, 146
Henle’s loops, 156
Hepatic artery, 109, 150
duct, 143, 150
flexure, 145, 146
veins, 110
Hernia, 146, 164
Hiccough, 99, 131
Highmore, antrum of, 54, 57
Hilum of kidney, 155
Hip-joint, 192
Housemaid’s knee, 194
Humerus, 175
Humors of eye, 70
Humpback or Pott’s disease, 91
Hydrocarbons, 12
Hydrocephalus, 34
Hydrochloric acid, 139, 140
Hydrothorax, 34
Hymen, 170
Hyoid bone, 60
Hypermetropia or far-sightedness, 72, 73
Hypochondriac regions, 135
Hypogastric plexus, 87
region, 135
Hypoglossal nerve, 84

Idiocy, 53
Ileo-cecal valve, 142, 145
Ileo-pectineal line, 163
Ileum, 142
Iliac artery, common, 107, 109
deep circumflex, 198
external and internal, 95, 109, 198
fosssæ, 163
Ilio-hypogastric nerve, 85
Ilio-inguinal nerve, 85
Ilium, 161, 162
Impacted hip, 193
Incisor teeth, 60
Incus, 63
Infundibula of lung, 125, 127
Inguinal regions, 135
Innominate artery, 107
bone, 161, 162
veins, 109
Inorganic compounds in body, 12
Intercostal arteries, 95, 97, 100, 108
muscles, 98, 128
nerves, 85, 97, 99, 134
Intercellular substance, 14, 17
Interossei muscles, 184
Interosseous nerves, 85, 186
Internal secretion, 36
Intervertebral foramen, 90
Intestines, 141, _et seq._
large, 141, 145
function, 146
glands, 145
nerves, 145
structure, 145, 146
small, 141, 142, _et seq._
blood-vessels, 143
function, 143, 144
glands, 142, 143
nerves, 143
structure, 142
Intima, 27
Intralobular vein, 150
Intussusception, 146
Involuntary muscle, 21
Iris, 68, 69, 72
Ischium, 161, 163
Island of Reil, 75

Jaundice, 35, 152, 153, 158
Jejunum, 142
Joints, 15, 20
classes of, 20, 21
ankle, 195
elbow, 21, 185
hip, 21, 192
knee, 193
motion of, 20, 21
shoulder, 21, 185
wrist, 185
Jugular veins, 109
Juice, gastric, 139
pancreatic, 143, 144, 153

Katabolism, 147
Kidneys, 155, _et seq._
floating, 159
function, 156, _et seq._
position, 155
structure, 155, 156
Knee-jerk, 83
Knee-joint, 193

Labia majora, 169
minora or nymphæ, 170
Labyrinth, membranous, 64, 65
osseous, 64
Lachrymal bones, 48, 54
canal, 54, 57
duct, 68
gland, 68
sac, 54, 68
Lacteals, 32, 144
Lacunæ of bone, 17
Lambdoidal suture, 48
Lamellæ of bone, 17
Laminæ of vertebræ, 89
Large intestine, 141, 145
Laryngitis, 122
Laryngotomy, 122
Larynx, 121
Latissimus dorsi, 93
Laughing, 131
Lens, crystalline, 69, 70
Leucocytes, 33, 34, 119, 120
Levator scapulæ, 93
Levatores of ribs, 129
Lieberkühn, glands of, 143, 144, 145
Ligaments, 15, 20, 21
annular, 184, 198
broad, of uterus, 165, 166, 168
capsular, of hip, 21, 193
crucial, of knee, 193
orbicular, 178
Poupart’s, 132
round, of uterus, 168
suspensory, of liver, 149
thyro-arytenoid, 122
Ligamentum nuchæ, 50, 91, 93
patellæ, 190, 192, 193, 194
teres, 187
Line, Nélaton’s, 189
Linea alba, 132
aspera, 187
Liver, 36, 149, _et seq._
blood supply, 150
diseases of, 152
function, 150, _et seq._
position, 149
structure, 149, 150
Loops of Henle, 156
Lower extremities, 187, _et seq._
Lumbar artery, 95, 109
fascia, 133
nerves, 84, 85
plexus, 84
regions, 135
vertebræ, 90
Lumbricales, 184
Lungs, 125, _et seq._
function, 127, _et seq._
nerves, 127
position, 126
structure, 126, 127
Lupus, 58
Lymph, 30, 32
capillaries, 30
character, 32, 33
flow of, 33
function, 34
spaces, 30
transudation of, 33
Lymphatic glands, 32, 34, 35
system, 27, 29, _et seq._
vessels, 30, 31
valves of, 31, 32, 33

Macula lutea, 70
Malar or cheek bone, 48, 54
Malaria, 154
Male organs of generation, 163, 164, 165
Malleolus of fibula, 194, 195
of tibia, 194
Malleus, 63
Malpighian bodies, 156
pyramids, 156
Mammary artery, internal, 99, 100, 108
glands, 99, 100
Manubrium, 97
Marrow of bone, 18
Masseter, 51, 54
Mastoid abscess, 51, 52
cells, 51, 64
portion of temporal bone, 51
Maxillary bone, inferior, 48, 55
superior, 48, 54
McBurney’s point, 145
Meatus, auditory, 52, 65
nasal, 57
urinarius, 160, 165, 170
Median, cephalic vein, 109
nerve, 85, 186
vein, 109
Mediastinal artery, 99
Mediastinum, 32, 126
Medulla or marrow, 18
Medulla oblongata, 78, 79, 82
Medullary artery, 19
canal, 19
sheath, 37
Meibomian duct, 74
glands, 67
Membrana tympani or drum, 63
Membranous labyrinth, 64, 65
Mesenteric arteries, 109, 143, 145, 153
veins, 110, 150
Mesenteries, 32, 134
Metabolism, 45, 147, 151, 152
Metacarpal bones, 181
Metatarsal bones, 195
Micturition, 157
Milk teeth, 60
Mitral valve, 104
Molar teeth, 60
Monometer, 114
Mons Veneris, 169
Motor areas, 81, 82
center, 81, 82
oculi nerve, 68, 83
tract, 82
Mouth, 59, _et seq._
Mucous membrane, 40
Mucus, 40
Mumps, 62
Muscle, 21, _et seq._
action, 23, 24
cardiac, 22, 25
characteristics, 22, 23, 24, 25
classes of, 21
fatigue of, 26, 27
function of, 24
smooth, 21, 25
sounds, 25
striated, 21, 23, 25
work, 25, 26
Muscles of abdomen, 132, _et seq._
of arm, 175, 176, 177
of back, 93, 94
of chest, 98, 99, 128
of foot, 198
of forearm, 182
of hand, 184
of head, 50, 51, 54, 55, 58, 67, 69
of leg, 196, _et seq._
of neck, 51, 92, 93, 129
of shoulder, 174
of thigh, 189, _et seq._
Musculo-cutaneous nerve, 85, 186, 199
Musculo-spiral nerve, 85, 175, 186
Musical sounds, 65
Myopia or near-sightedness, 72, 73
Myosin, 11, 23
Myosinogen, 23

Nails, 27, 40
Nares, 57
Nasal bones, 55
duct, 68
fossæ, 55, 57
meatus, 57
Nasal septum, 55
Navicular or scaphoid bone, 195
Near-sightedness, 72, 73
Neck, glands of, 32
muscles of, 51, 92
Nélaton’s line, 189
Nerve, 37
action of, 37, 38, 83
cell or gray matter, 36
fiber or white matter, 36
function, 37
ganglia, 87, 110
motor, 82
plexus, 29, 84, _et seq._
sensory, 82, 83
terminations, 37
Nerves, 24, 36
abducens, 83
auditory, 64, 65, 84
cardiac, 78
cervical, 84
circumflex, 85, 186
coccygeal, 84
cranial, 77, 78, 83, 84
crural, anterior, 85, 199
cutaneous, 46, 85
dorsal or thoracic, 84, 85
eighth, 64, 84
eleventh, 84
facial, 83
fifth, 83
first, 83
fourth, 68, 83
genito-crural, 85
glosso-pharyngeal, 61, 84
gluteal, 199
hypoglossal, 84
ilio-hypogastric, 61, 85
ilio-inguinal, 85
intercostal, 85, 97, 99, 134
interosseous, 85, 186
lumbar, 84, 85
median, 85, 186
motor oculi, 68, 83
musculo-cutaneous, 85, 186, 199
musculo-spiral, 85, 175, 186
ninth, 84
obturator, 85
olfactory, 53, 58, 83
optic, 70, 71, 76, 83
patheticus, 83
phrenic, 85, 99, 130
plantar, 85
pneumogastric, 84, 110, 111, 127, 130, 153
popliteal, 85, 199
post-tibial, 85
radial, 85
sacral, 84
sciatic, 85, 163, 199
second, 70, 83
seventh, 83
sixth, 68, 83
spinal, 84, 95
accessory, 84, 95, 137
suprascapular, 186
sympathetic, 87, 110, 127, 137, 143, 145, 168
tenth, 84
third, 68, 72, 83
thoracic, 186
cutaneous, 100
tibial, 86, 87, 199
trifacial, 61, 83
twelfth, 84
ulnar, 85, 175, 186
vagus, 84, 110, 111, 127, 130, 153
vasoconstrictors, 115
dilators, 115
motor, 29, 78, 115
Nervous system, 38, 75, _et seq._
tissue, 13, 36
Neurilemma, 37
Ninth nerve, 84
Nipple, 100
Nose, 57, 58
bleed, 59
Nucleolus, 12
Nucleus, 12
Nutrient foramen, 19
Nymphæ, 170

Oblique muscles of abdomen, 132
of eye, 68
Obturator foramen, 163
nerve, 85
Occipital bone, 48, 50
Occipito-frontalis muscle, 51
Odontoid process of axis, 91
Olecranon fossa, 175
process, 178
Olfactory bulbs, 53, 58, 76
cells, 58
grooves, 53
nerves, 53, 58, 83
tract, 58, 76
Omenta, 134, 146
Ophthalmic artery, 70
Optic axis, 70
commissure, 76
foramen, 66, 70
nerve, 70, 71, 76, 83
tract, 76
Orbicular ligament, 178
Orbicularis palpebrarum, 67
Orbit of eye, 54, 66
Organ of Corti, 65
Organic compounds in body, 11, 12
Os calcis, 195
innominatum, 161, 162
magnum, 181
uteri, 168
Osseous labyrinth, 64
Ossicles of ear, 63, 65
Osteoblasts, 18
Osteomalacia, 164, 189
Osteomyelitis, 193
Oval window, 63, 64, 65
Ovaries, 165
Ovum, 12, 166, 168
Oxyhemoglobin, 130

Paget’s disease, 53
Pain, sensation of, 47, 81
Palate, bones of, 48, 54
cleft, 55
hard, 55, 59
soft, 59, 60, 136
Palmar, arch, 186
fascia, 184
Palmaris longus, 182, 183
Pancreas, 153
Pancreatic duct, 143, 153
juice, 143, 144, 153
Pancreatitis, 153
Panhysterectomy, 169
Papillæ of skin, 37, 39
of tongue, 61
Paralysis, 79
Parietal bone, 48, 49
Parotid gland, 51, 62
Patella or knee-cap, 19, 192
Patheticus nerve, 83
Pectoral muscles, 99, 128
Pectoralis major, 174
Pedicles of vertebræ, 89
Pelvis, 132, 161, _et seq._
false, 163
of kidney, 156
true, 163, 164
Penis, 160, 165
Pepsin, 140
Peptones, 12, 140, 150
Pericardium, 34, 101, 102
Perichondrium, 16
Perineal body, 170
Perineum, 170
Perilymph, 64, 65
Periosteum, 15, 18, 19, 76
Peripheral resistance, 112, 114
Peristaltic movements, 138, 143, 146
Peritoneum, 134
Permanent teeth, 60
Peroneal artery, 199
Peroneus brevis, 197
longus, 197
Petrous portion of temporal bone, 51, 52
Peyer’s patches or glands, 142
Phalanges of foot, 195
of hand, 181
Pharynx, 59, 136, 137
Physiology, 11
Phrenic artery, 99, 109
nerve, 85, 99, 130
Pia mater, 76
Pigeon breast, 97
Pillars of the fauces, 59, 60
Pink eye, 74
Pinna, 63
Pisiform bone, 181
Pituitary body, 36
Placenta, 106, 107
Plantar artery, 199
fascia, 198
nerve, 86
Plantaris, 197
Plasma of blood, 33, 116, 117
Platysma myoides, 92
Pleuræ, 34, 125
Plexus, 29
brachial, 84, 85
cardiac, 87
cervical, 84
hypogastric, 87
lumbar, 84
sacral, 84, 85
solar, 87, 153
Pneumogastric nerve, 84, 110, 127, 153
Polypi, 58
Pons Varolii, 78
Popliteal artery, 198
nerves, 86, 199
space, 32, 198
Popliteus muscle, 198
Portal circulation, 110
vein, 110, 150
Pott’s disease, 91
fracture, 180, 195
Poupart’s ligament, 132
Prepatella bursa, 192
Prepuce, 165
Presbyopia, 73
Presternal notch, 171
Procreating glands, 165
Profunda artery, 175, 186
femoris artery, 198
Promontory of the sacrum, 90
Pronator quadratus, 182, 183
radii teres, 182, 183
Prostate gland, 164, 165
Proteins, 11, 26, 33, 140, 144, 147, 148
Protoplasm, 12, 13
Psoas magnus, 189, 190
parvus, 190
Ptosis of liver, 152
of upper lid, 74
Ptyalin, 61, 136
Pubes, 161, 163
Pudic artery, 168
Pulmonary artery, 106, 110
circulation, 110
valves, 104
veins, 105, 110
Pulse, 112, 113, 114, 115
Pulse, causes, 112
dicrotic, 113
rate, 111, 113, 114
Pupil of eye, 69, 72
Pus corpuscles, 120
Pylorus, 138
Pyramidalis muscle, 134
Pyramids, Malpighian, 156

Quadratus lumborum, 134
Quadriceps extensor, 190

Radial artery, 108, 185
nerve, 85
Racemose glands, 35
Radius, 178, 179
Râles, 129
Receptaculum chyli, 32
Recti muscles of eye, 67, 72
Rectum, 145, 146
Rectus abdominis, 133, 134
capitis anticus major, 93
femoris, 190
Red corpuscles, 118, 119
Reflex action, 83
Regions, abdominal, 134, 135
Renal artery, 109
Rennin, 140
Respiration, 121, 127, _et seq._
center of, 78, 130
effect on air, 129, 130
effect on blood, 130, 131
forced, 128, 129
kinds of, 128
rate, 128
sounds, 129
variations in, 131
Retching, 140
Retina, 68, 69, 70
Rheumatism, 25
Rhomboideus muscles, 93
Rickets, 19, 49, 53, 97, 164, 195
Ribs, 97, 98
Right lymphatic duct, 31, 32
Rigor mortis, 22, 23
Rivinus, ducts of, 62
Rodent ulcer, 74
Rods and cones, 69, 70
Rolando, fissure of, 75, 82
Rosary, 97
Round ligament of uterus, 168
Round window, 64, 65
Rupture, 146, 164
of kidney, 158
of liver, 152
of spleen, 154
of urethra, 160

Sacral nerves, 84
plexus, 84, 85
vertebræ, 90
Sacro-sciatic notch, 163
Sacrum, 90, 161
Sagittal suture, 48
Saliva, 61, 136
Salivary glands, 35, 61, 136
Salpingectomy, 169
Saphenous veins, 109, 199
Sarcolemma, 21
Sarcoma, 173, 177, 193
Sartorius muscles, 23, 190
Scalenus muscles, 93, 128
Scaphoid bone, ankle, 195
wrist, 181
Scapula, 173
Scarlet fever, 35
Scarpa’s triangle, 190, 198
Schwann, white substance of, 37
Sciatic nerve, 85, 163, 199
Sclera or sclerotic coat, 68
Scrotum, 165
Sebaceous glands, 35, 40, 41
Sebum, 41
Second nerve, 70, 83
Secreting glands, 35
Segmentation, growth by, 12
Semen, 165
Semicircular canals, 64, 66
Semilunar bones, 181
cartilages, 193, 194
valves, 28, 32, 104
Semimembranosus muscle, 191
Semitendinosus muscle, 191
Sense, organs of, 57, _et seq._
of hearing, 65
of sight, 70, _et seq._
of smell, 55, 57, 58, 61
of taste, 55, 61
of touch, 45, _et seq._
Sensory nerves, 82, 83
tract, 82
Septum of nose, 55
deviation of, 58
Serous membrane, 40
Serratus magnus, 174
Serum albumin, 11
of blood, 117
Sesamoid bones, 19
Seventh nerve, 83
Shin, 194
Shoulder girdle, 171
joint, 185
Sighing, 131
Sight, sense of, 70, _et seq._
Sigmoid cavities, 178
flexure, 145, 146
Silent areas in brain, 82
Silver fork deformity, 180
Sinuses, 28, 49, 51, 52, 78, 105
Sixth nerve, 68, 83
Skin, 39, _et seq._
Skull, bones of, 48, _et seq._
Small intestine, 141, 142, _et seq._
Smell, sense of, 55, 57, 58, 61
Smooth muscle, 21, 25
Sneezing, 131
Sobbing, 131
Soft palate, 59, 60, 136
Solar plexus, 87, 153
Soleus, 196
Solitary glands, 142, 145
Sounds, 65, 66
Special senses, 57, _et seq._
Speech, 122
center, 82
Spermatic or ovarian artery, 109, 168
cords, 165
Spermatozoa, 165
Sphenoid bone, 48, 52
Sphincter of anus, 146
of pupil, 72
of pylorus, 138
Spina bifida, 91
Spinal accessory nerve, 84, 95, 137
canal, 91
column, 88
cord, 79, _et seq._
foramen, 89
nerves, 84, 95
Spine, 87
Spinous process of vertebræ, 89
Spleen, 153, 154
Splenic artery, 109, 153
flexure, 145, 146
vein, 110, 150
Sprain, 21
Squamous portion of temporal bone, 51
Stapes, 63
Starches, 12, 136, 144
Steapsin, 144
Stensen’s duct, 62
Sterno-cleido-mastoid muscle, 51, 92, 171
Sternum, 97
Stimuli, 24
Stomach, 138
arteries, 139
digestion in, 139, 140
glands, 139
position, 138
structure, 139
Stomach teeth, 60
Strabismus, 72
Striated or striped muscle, 21, 23, 25
Stricture of esophagus, 138
of urethra, 160
Sty, 74
Styloid process of fibula, 195
of radius, 178, 179
of temporal bone, 52
of ulna, 178, 179
Subarachnoid space, 76, 79
Subclavian arteries, 94, 99, 107, 108, 185
veins, 109
Subclavius muscle, 173
Subdural space, 76
Sublingual gland, 56, 62
Submaxillary gland, 56, 62
Succus entericus, 143, 144
Sugar in urine, 151, 158
Superciliary ridges, 49
Supinator brevis, 182, 184
longus, 182, 184
Supraorbital foramen or notch, 49
vessels and nerve, 49
Suprarenal artery, 109
capsules, 36, 154
Suprascapular artery, 94
nerve, 186
Suspensory ligament of lens, 70, 72
of liver, 149
Sutures, 48, 53
coronal, 48
lambdoidal, 48
sagittal, 48
Sweat, composition, 42
functions, 42
glands, 35, 42
nervous control of, 42
quantity, 43
Sylvius, fissure of, 75
Sympathetic nerve, 87, 110, 127, 137, 143, 145, 168
system, 75, 87
Symphysis pubis, 163
Synovial fluid, 20, 34
membrane, 20
Syphilis, 35, 58, 122, 152, 182, 194
Systemic circulation, 105, 106, 107, _et seq._, 112, 113
Systole, 104, 106, 112

T-fracture, 177, 193
Tablets of skull, 20, 48
Tactile corpuscles, 37, 39, 46
Tarsus or ankle, 195
Taste buds, 61
nerves of, 61
sense of, 55, 61
Tears, 68
Teeth, 27, 60
Temperature of body, 43
regulation of, 43
sensation of, 47
variations in, 44
Temporal bone, 48, 51
muscle, 50, 51, 55
Temporary or milk teeth, 60
Tendo Achillis, 195, 197
Tendons, 15, 23
Tenth nerve, 84
Testes or testicles, 165
Third nerve, 68, 72, 83
Thoracic aorta, 99, 107, 109
duct, 31
nerves, 186
Thoracic cutaneous nerve, 100
Thorax, 96
Thymus gland, 36, 124
Thyro-arytenoid ligaments, 122
Thyroid axis, 108
cartilage, 121
gland, 36, 124
Tibia or shin bone, 194
Tibial artery, 198
nerve, 76, 87, 199
Tibialis anticus, 197
Tissues, areolar, 15
bony, 13, 17
cartilaginous, 13
connective, 13, 15
differentiation of, 13
elastic, 15
epithelial, 13
fibrous, 15
muscular, 13
nervous, 13, 36
Tongue, 46, 59, 60
tie, 62
Tonsillitis, 35, 62
Tonsils, 59, 62
Torticollis, 92
Touch, corpuscles, 37, 39, 46
sense of, 45, _et seq._
Trachea, 123
Tracheotomy, 123
Transudation of lymph, 33
Transversalis muscle, 133
colli artery, 94
Transverse colon, 145
processes of vertebræ, 89
Trapezium, 181
Trapezius, 93, 171
Trapezoid bone, 181
Triangular cartilage, 57
Triceps, 176, 177
Tricuspid valve, 104
Trifacial nerve, 61, 83
Trochanters, 189
Trochlear surface of femur, 189
of humerus, 175
True pelvis, 163, 164
ribs, 97
Trypsin, 144
Tuberculosis, 35, 122, 155, 159, 168, 182, 193, 194, 196
Tuberosities of humerus, 175
of tibia, 194
Tuberosity of ischium, 163
of radius, 178
Tubuli lactiferi, 100
Tumor albus, 194
Tumors, 100, 175
Tunica vaginalis oculi, 67
Turbinated bones, 48, 53, 54
Twelfth nerve, 84
Tympanum, 51, 63
Typhoid fever, 142, 154

Ulcer, 139
Ulna, 177, 178, 185
Ulnar artery, 108
nerve, 85, 175, 186
Umbilical artery, 107
region, 135
vein, 106
Unciform bone, 181
Unstriated or unstriped muscle, 21, 22, 25
Upper extremities, 171, _et seq._
Urea, 148, 152, 158
Ureters, 155, 156, 159
Urethra, 159, 160, 165
Urinary apparatus, 155, _et seq._
Urine, 156, _et seq._
Uterine artery, 168
Uterus, 167, 168
Uvula, 59

Vagina, 168
Vagus or pneumogastric nerves, 84, 110, 111, 130
Valves, 103
aortic, 104
bicuspid or mitral, 104
coronary, 105
Eustachian, 106, 107
ileo-cecal, 142, 145
of lymphatic vessels, 31, 32, 33
of veins, 28
pulmonary, 104
semilunar, 28, 32, 104
tricuspid, 104
Valvulæ conniventes, 142
Varicose veins, 109, 113, 199
Vas deferens, 165
Vasa nervorum, 37
vasorum, 29
Vasoconstrictor nerves, 115
dilator nerves, 115
motor nerves, 29, 78, 115
Vascular system, 107, et seq.
Vastus externus, 190
internus, 190
Veins, 27, 28, 29, 109
basilic, 109
deep, 28
gastric, 110, 150
hemorrhoidal, 146
hepatic, 110, 150
iliac, common, 109
inferior vena cava, 105, 109, 150
innominate, 109
intralobular, 150
jugular, 109
median, 109
cephalic, 109
mesenteric, 110, 150
portal, 110, 150
pulmonary, 105, 110
saphenous, 109, 199
splenic, 110, 150
subclavian, 109
superficial, 28
superior vena cava, 105, 109
umbilical, 106
valves, 28
varicosity, 109, 113, 199
Vena cava, inferior, 105, 109, 150
superior, 105, 109
Venæ comites, 27, 113
Ventricles of brain, 75, 79
of heart, 103
Vermiform appendix, 145
Vertebra prominens, 91
Vertebræ, 88, _et seq._
Vertebral arteries, 77
Vesiculæ seminales, 165
Vestibule of labyrinth, 64, 65
Vicarious function of glands, 35
Villi, 142
Viscera, abdominal, 135, _et seq._
Visual center, 81
Vital capacity, 129
Vitreous humor, 70
Vocal cords, 122
Volvulus, 146
Voluntary muscle, 21, 23
Vomer, 48, 55
Vomiting, 140
Vulva, 169

Wharton’s duct, 62
White corpuscles or leucocytes, 27, 33, 34, 119, 120
White substance of Schwann, 37
matter of brain and cord, 75, 76, 78, 80, 81
Willis, circle of, 78, 108
Wisdom teeth, 60
Wormian bones, 19, 49
Wrist, 180
joint, 185
Wry neck or torticollis, 92

Yawning, 131

Zygomatic process of temporal bone, 51, 54

SAUNDERS’ BOOKS FOR NURSES

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=Primary Studies for Nurses.= By CHARLOTTE
A. AIKENS, formerly Director of Sibley Memorial
Hospital, Washington, D. C. 12mo of 435 pages,
illustrated.
Cloth, $1.75 net.

Aikens’ Training-School Methods and the Head Nurse

This work not only tells how to teach, but also what should be taught
the nurse and _how much_. The _Medical Record_ says: “This book is
original, breezy and healthy.”

=Hospital Training-School Methods and the Head
Nurse.= By CHARLOTTE A. AIKENS, formerly
Director of Sibley Memorial Hospital, Washington,
D. C. 12mo of 267 pages.
Cloth, $1.50 net.

Aikens’ Clinical Studies for Nurses

ILLUSTRATED

This new work is written on the same lines as the author’s successful
work for primary students, taking up the studies the nurse must pursue
during the second and third years.

=Clinical Studies for Nurses.= By CHARLOTTE
A. AIKENS, formerly Director of Sibley Memorial
Hospital, Washington, D. C. 12mo of 512 pages,
illustrated.
Cloth, $2.00 net.

Fowler’s Operating Room NEW (2d) EDITION

Dr. Fowler’s work contains all information of a surgical nature that a
nurse must know in order to attain the highest efficiency. _Canadian
Journal of Medicine and Surgery_ says: “We find compactly and clearly
stated just those thousand and one things which when required are so
hard to locate.”

=The Operating Room and the Patient.=
By RUSSELL S. FOWLER, M. D., Professor of
Surgery, Brooklyn Postgraduate Medical School.
Octavo of 284 pages, with original illustrations.
Cloth, $2.00 net.

Fiske’s Anatomy and Physiology JUST READY

Miss Fiske weaves the physiology in with the anatomy, and in such a way
that both anatomy and function are readily understood and retained by
the reader.

=Anatomy and Physiology for Nurses.=
By ANNETTE FISKE. A. M., Graduate of the
Waltham Training School for Nurses, Massachusetts.
12mo of 250 pages, illustrated.

Beck’s Reference Handbook NEW (2d) EDITION

This book contains all the information that a nurse requires to carry
out any directions given by the physician. The _Montreal Medical
Journal_ says it is “cleverly systematized and shows close observation
of the sickroom and hospital regime.”

=A Reference Handbook for Nurses.=
By AMANDA K. BECK, Graduate of the Illinois
Training School for Nurses, Chicago, Ill. 32mo
volume of 200 pages. Bound in flexible leather,
$1.25 net.

Boyd’s State Registration for Nurses

This book tells the nurse just what she must know in order to obtain
a certificate in any State. It presents comparative summaries of the
laws, requirements, fees, exceptions and restrictions, violations and
their penalties. The work will also form a serviceable basis for the
drafting of laws.

=State Registration for Nurses.= By LOUIE
CROFT BOYD, R. N., Graduate Colorado Training
School for Nurses.
Price, 50 cents net.

DeLee’s Obstetrics for Nurses THIRD EDITION

Dr. DeLee’s book really considers two subjects--obstetrics for nurses
and actual obstetric nursing. _Trained Nurse and Hospital Review_ says
the “book abounds with practical suggestions, and they are given with
such clearness that they cannot fail to leave their impress.”

=Obstetrics for Nurses.= By JOSEPH B.
DELEE, M. D., Professor of Obstetrics at the
Northwestern University Medical School, Chicago.
12mo volume of 512 pages, fully illustrated.
Cloth, $2.50 net.

Davis’ Obstetric & Gynecologic Nursing

THE NEW (3d) EDITION

_The Trained Nurse and Hospital Review_ says: “This is one of the most
practical and useful books ever presented to the nursing profession.”
The text is illustrated.

=Obstetric and Gynecologic Nursing.=
By EDWARD P. DAVIS, M. D., Professor of
Obstetrics in the Jefferson Medical College,
Philadelphia. 12mo volume of 436 pages,
illustrated. Buckram, $1.75 net.

Macfarlane’s Gynecology for Nurses

ILLUSTRATED

_Dr. A. M. Seabrook_, Woman’s Hospital of Philadelphia, says: “It is a
most admirable little book, covering in a concise but attractive way
the subject from the nurse’s standpoint. You certainly keep up to date
in all these matters, and are to be complimented upon your progress and
enterprise.”

=A Reference Handbook of Gynecology for Nurses.=
By CATHARINE MACFARLANE, M. D., Gynecologist to
the Woman’s Hospital of Philadelphia. 32mo of 150
pages, with 70 illustrations.
Flexible leather, $1.25 net.

McKenzie’s Exercise in Education and Medicine

=Exercise in Education and Medicine.=
By R. TAIT MCKENZIE, B. A., M. D., Professor of
Physical Education, and Director of the Department,
University of Pennsylvania. Octavo of 406 pages,
with 346 illustrations.
Cloth, $3.50 net.

Manhattan Hospital Eye, Ear, Nose, and Throat Nursing

ILLUSTRATED

This is a practical book, prepared by surgeons who, from their
experience in the operating amphitheatre and at the bedside, have
realized the shortcomings of present nursing books in regard to eye,
ear, nose, and throat nursing.

=Nursing in Diseases of the Eye, Ear, Nose and
Throat.= By the Committee on Nurses of the Manhattan
Eye, Ear, and Throat Hospital: J. EDWARD GILES, M.
D., Surgeon in Eye Department; ARTHUR B. DUEL, M.
D., (chairman), Surgeon in Ear Department; HARMON
SMITH, M. D., Surgeon in Throat Department. Assisted
by JOHN R. SHANNON, M. D., Assistant Surgeon in
Eye Department; and JOHN R. PAGE, M. D., Assistant
Surgeon in Ear Department. With chapters by HERBERT
B. WILCOX, M. D., Attending Physician to the
Hospital; and Miss EUGENIA D. AYERS, Superintendent
of Nurses. 12mo of 260 pages, illustrated. Cloth,
$1.50 net.

Friedenwald and Ruhrah’s Dietetics for Nurses NEW (2d) EDITION

This work has been prepared to meet the needs of the nurse, both in
training school and after graduation. _American Journal of Nursing_
says it “is exactly the book for which nurses and others have long and
vainly sought.”

=Dietetics for Nurses.= By JULIUS
FRIEDENWALD, M. D., Professor of Diseases
of the Stomach, and JOHN RUHRAH, M. D.,
Professor of Diseases of Children, College of
Physicians and Surgeons, Baltimore. 12mo volume
of 395 pages.
Cloth, $1.50 net

Friedenwald & Ruhrah on Diet THIRD EDITION

=Diet in Health and Disease.= By JULIUS
FRIEDENWALD, M. D., and JOHN RUHRAH,
M. D. Octavo volume of 764 pages.
Cloth, $4.00 net.

Galbraith’s Personal Hygiene and Physical Training for Women

JUST ISSUED

=Personal Hygiene and Physical Training for Women.=
By ANNA M. GALBRAITH, M. D., Fellow New York Academy
of Medicine. 12mo of 371 pages, illustrated.
Cloth, $2.00 net.

Galbraith’s Four Epochs of Woman’s Life THE NEW (2d) EDITION

=The Four Epochs of Woman’s Life.= By ANNA
M. GALBRAITH, M. D. With an Introductory Note
by JOHN H. MUSSER, M. D., University of
Pennsylvania. 12mo of 247 pages.
Cloth, $1.50 net.

McCombs’ Diseases of Children for Nurses

JUST ISSUED--NEW (2d) EDITION

Dr. McCombs’ experience in lecturing to nurses has enabled him to
emphasize _just those points that nurses most need to know. National
Hospital Record_ says: “We have needed a good book on children’s
diseases and this volume admirably fills the want.” The nurse’s side
has been written by head nurses, very valuable being the work of Miss
Jennie Manly.

=Diseases of Children for Nurses.=
By ROBERT S. MCCOMBS, M. D., Instructor of
Nurses at the Children’s Hospital of Philadelphia.
12mo of 470 pages, illustrated.
Cloth, $2.00 net

Wilson’s Obstetric Nursing

In Dr. Wilson’s work the entire subject is covered from the beginning
of pregnancy, its course, signs, labor, its actual accomplishment, the
puerperium and care of the infant. _American Journal of Obstetrics_
says: “Every page emphasizes the nurse’s relation to the case.”

=A Reference Handbook of Obstetric Nursing.=
By W. REYNOLDS WILSON, M. D., Visiting
Physician to the Philadelphia Lying-in Charity. 32mo
of 355 pages, illustrated.
Flexible leather, $1.25 net.

American Pocket Dictionary NEW (6th) EDITION

The _Trained Nurse and Hospital Review_ says: “We have had many
occasions to refer to this dictionary, and in every instance we have
found the desired information.”

=American Pocket Medical Dictionary.= Edited by
W. A. NEWMAN DORLAND, A. M., M. D., Loyola
University, Chicago.
Flexible leather, gold edges, $1.00 net;
with patent thumb index, $1.25 net.

Lewis’ Anatomy and Physiology SECOND EDITION

_Nurses Journal of Pacific Coast_ says “it is not in any sense
rudimentary, but comprehensive in its treatment of the subjects.” The
low price makes this book particularly attractive.

=Anatomy and Physiology for Nurses.=
By LEROY LEWIS, M. D., Lecturer on Anatomy and
Physiology for Nurses, Lewis Hospital, Bay City,
Mich. 12mo of 375 pages, 150 illustrations.
Cloth, $1.75 net.

Dorland’s Illustrated Dictionary NEW (5th) EDITION

=The American Illustrated Medical Dictionary.=
Edited by W. A. N. DORLAND, M. D. Large
octavo of 876 pages, 293 illustrations, 119 in
colors. Flexible leather, $4.50 net; thumb indexed,
$5.00 net.

Paul’s Materia Medica

=A Text-Book of Materia Medica for Nurses.=
By GEORGE P. PAUL, M. D., Samaritan Hospital,
Troy, N. Y. 12mo of 240 pages.
Cloth, $1.50 net.

Paul’s Fever Nursing

=Nursing in the Acute Infectious Fevers.=
By GEORGE P. PAUL, M. D.
Cloth, $1.00 net.

Hoxie’s Medicine for Nurses

=Practice of Medicine for Nurses.=
By GEORGE HOWARD HOXIE, M. D., University
of Kansas. With a chapter on Technic of Nursing
by PEARL L. LAPTAD. 12mo of 284 pages,
illustrated.
Cloth, $1.50 net.

Grafstrom’s Mechano-therapy SECOND EDITION

=Mechano-therapy (Massage and Medical
Gymnastics).= By AXEL V. GRAFSTROM,
B. Sc., M. D., 12mo, 200 pages.
Cloth, $1.25 net.

Nancrede’s Anatomy NEW (7th) EDITION

=Essentials of Anatomy.= CHARLES B. G.
DENANCREDE, M. D., University of Michigan.
12mo, 400 pages, 180 illustrations.
Cloth, $1.00 net.

Morrow’s Immediate Care of Injured

=Immediate Care of the Injured.= By ALBERT
S. MORROW, M. D., New York City Home for
Aged and Infirm. Octavo of 340 pages, with 238
illustrations. Cloth, $2.50 net.

=A Text-Book on Practical Fever Nursing.=
By EDWARD C. REGISTER, M. D., North Carolina
Medical College. Octavo of 350 pages, illustrated.
Cloth, $2.50 net.

Pyle’s Personal Hygiene NEW (4th) EDITION

=A Manual of Personal Hygiene.= Edited by
WALTER L. PYLE, M. D. Wills Eye Hospital,
Philadelphia. 12mo, 472 pages, illus.
$1.50 net.

Morris’ Materia Medica NEW (7th) EDITION

=Essentials of Materia Medica, Therapeutics,
and Prescription Writing.= By HENRY MORRIS,
M. D. Revised by W. A. BASTEDO, M. D.,
Columbia University, N. Y. 12mo of 300 pages,
illustrated. Cloth, $1.00 net.

Griffith’s Care of the Baby JUST ISSUED NEW (5th) EDITION

=The Care of the Baby.= By J. P. CROZER
GRIFFITH, M. D., University of Pennsylvania.
12mo of 455 pages, illustrated.
Cloth, $1.50 net.

*** End of this LibraryBlog Digital Book "Structure and Functions of The Body - A Hand-Book of Anatomy and Physiology for Nurses and others desiring a Practical knowledge of the Subject" ***

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