ear to the throat and known as the Eustachian tube; stoppage of this
tube in chronic inflammation of the throat is one of the causes of
FIG. 26. Section of the Eye. i, Conjunctiva; 2, cornea; 3, 3, iris; 4, pupil; 5, lens;
6, retina; 7, optic nerve.
The sense of sight consists in the perception of light, color, form,
size, and distance ; it is resident in the eye.
The eye (Fig. 26) is situated in the orbit, the projecting upper
border of which, together with the quickly moving lids, give it pro-
tection. It is covered in front by a thin vascular membrane which
also lines the lids and is known as the conjunctiva. Light enters
through the transparent cornea which is set in front of the eye like
a watch-glass ; behind the cornea is hung a curtain of muscular fibers
variously colored and called the iris; the black pupil is really a hole
in the iris to let in the light which then passes through a crystalline
lens just behind the pupil and is brought to a focus on the retina; the
60 ANATOMY AND PHYSIOLOGY
retina is merely an expansion of the optic nerve which transmits the
luminous impressions to the brain. The dense white outer coat of
the eye, lying beneath the conjunctiva, is known as the sclerotic.
The eye is a camera, focusing being accomplished by changes in
the convexity of the lens effected by the contraction of the ciliary
muscle, the muscle of accommodation.
Color-blindness is the inability to distinguish certain colors, par-
ticularly reds and greens.
THE DIGESTIVE APPARATUS
INASMUCH as the nutritive constitutents of the blood are being
constantly used up in the repair of tissue and the production of heat
and force, it is necessary that some provision should be made for a
constant supply of new material. This is done by the food through
the digestive apparatus ; the function of the digestion is to prepare
the food for absorption and nutrition.
Foods are usually classified according to certain definite com-
pounds or alimentary principles which they contain ; these are four
in number: i. Albuminates, nitrogenous substances or proteids;
2. Fats or hydrocarbons; 3. Starches and sugars or carbohydrates;
4. Minerals, including water and salts.
The especial uses of these alimentary principles in nutrition are as
follows : The albuminates are essential for the repair of all the
nitrogenous constituents of the body, that is to say, they are muscle
and blood builders ; they regulate the absorption and use of oxygen ;
they sometimes form fat, and hence force and heat. The fats
produce force and heat, prevent the waste of the nitrogenous tissues,
and serve as a reserve of heat and force. The starches and sugars
also are readily convertible into heat and work, and, though they
have little part in the composition of the tissues of the body, they
contribute directly or indirectly to the deposit of fat. Water con-
stitutes nearly 60 per cent of the human body and is the most im-
portant constituent of foods ; without the other foods one may live
weeks, but without water it is a question of a very few days. Water
is the great solvent without which even the circulation of the blood
can not go on.
The various salts are also essential ; the alkaline carbonates formed
from the salts, of the vegetable acids maintain the necessary alka-
linity of the blood and body fluids ; without a due proportion of them
All these alimentary principles are necessary for life; some one or
ANATOMY AND PHYSIOLOGY
more of them are contained in all foods; if any one food contained
them all in proper proportion that substance would constitute a com-
plete diet ; milk contains them all and in a complete form for infants,
but for adults a mixed diet is necessary. Beef consists largely of
albuminates, pork of fats, bread of starch, candies of sugar.
FIG. 27. View of Thoracic and Abdominal Organs; anterior walls removed, but the
relative position of the ribs, navel, etc., indicated, a, Heart; b, great vessels; c, c, lungs;
d, d, diaphragm; e, liver; /, gall bladder; g, stomach; h, spleen; i, ascending colon;
), transverse colon; k, coils of small intestine; /, position of ileo-cecal valve at junction of
small and large intestines; m, urinary bladder.
The proper quantity of the various articles of food necessary per
day to maintain a man in good health while performing ordinary
labor constitutes a ration.
Great exertion calls for an increase of the albuminates and fats,
while great cold demands a special increase of the fats.
Now these alimentary principles, in the form in which they exist
in foods, are not ready for absorption; they must be reduced to
soluble forms : the albuminates to peptones, the sugars and starches
THE DIGESTIVE APPARATUS 63
to glucose, and the fats to an emulsion ; to accomplish this is the
purpose of the digestive apparatus.
When too much food is taken the excess is not digested but acts
as a foreign body and causes irritation of the stomach and bowels,
followed by pain and diarrhea, or the poisonous products of decom-
position are absorbed, causing fever auto-intoxication.
A deficiency of food causes the tissues of the body to be drawn
upon and emaciation is the result.
The apparatus for the digestion of the food consists of the
alimentary canal, and the salivary glands, liver, spleen, and pancreas.
The alimentary canal includes the mouth, pharynx, oesophagus,
stomach, small intestine, and large intestine; it is a muscular tube
lined with mucous membrane, about thirty feet long and extending
from the lips to the anus (Fig. 27).
In the mouth provision is made for the mastication of the food and
its admixture with saliva ; beyond this is the apparatus for swallow-
ing, the pharynx and oesophagus, which convey the food to the
stomach, where a partial reduction and solution of it take place ; in
the small intestine the digestion and solution are completed, and the
nutritive principles, composing the chyle, are separated, by its admix-
ture with the bile and pancreatic juice, from that portion which
passes into the large intestine, most of which is expelled from the
In looking into the mouth (Fig. 28), we see the teeth and tongue,
already described, and, stretching across the upper and back part,
a fleshy curtain known as the palate; hanging down from the center
of the palate is the uvula, and on either side behind the palate are
In the mouth the food is thoroughly broken up by the teeth and,
assisted by the tongue, mixed with the saliva, and formed into a
suitable lubricated mass for swallowing.- The only digestion which
takes place in the mouth is the slight conversion of the starch into
sugar ; nevertheless thorough mastication is of the greatest impor-
tance, as, the more completely the food is broken into small particles,
the more easily the digestive fluids of the stomach and intestines
get at the particles to dissolve them. If we wish to dissolve out the
soluble constituents of a crude drug, we first pulverize it in a mortar,
and the same principle obtains here.
After the food has been masticated it is pushed into the pharynx
64 ANATOMY AND PHYSIOLOGY
by the tongue and there passes beyond the control of the will through
the eight or nine inches of the oesophagus or gullet into the stomach.
The saliva comes from the salivary glands, which are three in
number on each side, the parotid, submaxillary, and sublinguaL The
parotid glands are situated just in front of and below the ear, and are
FIG. 28. Section of Head and Neck.
the seat of the inflammation known as mumps. The other salivary
glands are placed below the tongue and lower jaw.
The stomach (Fig. 29) is a muscular bag lined with mucous mem-
brane, pear shaped, with the large end to the left and lying on the
upper part of the abdomen, largely behind the ribs, and separated
from the thoracic cavity by the diaphragm. The heart is just above
it, with only the diaphragm between, so that it can easily be seen how
distention of the stomach may cause disturbances of the heart and
how pains in the stomach are so often referred to the heart.
The stomach opens into the oesophagus at one end and into the
small intestine at the other by small openings known as the cardiac
THE DIGESTIVE APPARATUS 65
and pyloric orifices, respectively. The small intestine is about twenty-
five feet long, and lies in the central and lower part of the abdomen,
extending from the stomach to the right groin, where it terminates
in a valvular opening into the large intestine.
The large intestine is about five feet long. It commences at the
termination of the small intestine in the right groin, this part of it
being known as the cecum and having attached to its lower and
FIG. 29. Stomach.
back part a tail-like appendage known as the vermiform appendix;
this appendix, about the size of a goose quill and two to five inches
long, is the part which is so frequently inflamed, constituting the
disease called appendicitis.
The cecum as it passes up the right side of the abdomen is known
as the ascending colon; under the liver it turns and crosses to the
left in front of the stomach, becoming the transverse colon; en the
left side of the abdomen it turns downward, the descending colon;
in the left groin it makes a curve like the letter S, the sigmoid flexure,
and ends in the rectum, which descends to the right and backward
to the anus.
The intestines are covered with a smooth, shining membrane
which lines the abdomen and is known as the peritoneum; inflam-
mation of this membrance is called peritonitis.
The omentum is a sort of apron made of a fold of the peritoneum,
containing much fat, which lies over the intestines and protects them.
The mesentery is the name applied to other folds of the peritoneum
06 ANATOMY AND PHYSIOLOGY
which bind the intestines loosely to the abdominal walls behind
them. In the abdominal walls are certain weak places where blood-
vessels pass out of the cavity and the intestines have a tendency to
follow the vessels ; these places are the umbilicus or navel, the in-
guinal canal, along which the vessels pass to the testicle, and the
femoral canal, for those to the thigh. When the intestine does so
escape we have hernia, umbilical, inguinal, or femoral, respectively.
FIG 30. Pancreas in Section to Show Its Duct.
In the upper part of the abdomen, on the right side and extending
somewhat to the left, we have the liver (Fig. 27) ; it is the largest
gland in the body, weighing between four and four and a half pounds,
and in its natural state lies almost wholly behind the ribs. The
liver has two large lobes, between which and projecting just beyond
the ribs is the gall bladder, which empties by a narrow duct into the
small intestine just beyond the stomach.
-To the left of the stomach and also behind the ribs is another
gland, which has no duct, called the spleen; it is dark colored and
about the size and shape of the hand without the fingers.
Deeply placed behind the stomach and extending transversely
across the abdomen is a slender tongue-shaped gland, the pancreas
or siveetbread (Fig. 30). It is about six inches long by three-fourths
of an inch broad, cream colored, and has a duct which terminates in
the small intestine together with the common bile duct.
In the stomach the food which has already been masticated and
part of the starch converted into glucose by the action of the saliva
is brought into contact with the gastric juice; this juice is a sour
liquid, containing' pepsin and hydrochloric acid, secreted by the
countless small glands found in the mucous lining of the stomach.
This is the same pepsin and hydrochloric acid which are used outside
the body to digest milk and other albuminates. The contraction of
THE DIGESTIVE APPARATUS 67
the muscular walls of the stomach caused by the presence of food
thoroughly mixes it with the gastric juice, and continues this churn-
ing motion as long as the food remains.
Under this process albuminates are partially converted into pep-
tones, a form suitable for absorption, and part of these peptones are
immediately absorbed by the capillaries of the stomach. The solu-
tion of the albuminous intercellular materials aids in the liquefaction
of other food principles, which pass slowly out of the stomach into
the intestine in the form of a whitish fluid known as chyme. The
process of stomach digestion requires from one to four hours, de-
pending upon the character of the food, the thoroughness of mastica-
tion, and other factors. Thus fish and chicken are more quickly
digested than beef, and beef sooner than veal, baked and stewed
meats sooner than the same articles fried.
The mucous lining of the small intestine is thrown into numerous
folds known as valvulce conniventes, the purpose of which is to in-
crease the extent of surface and this is still further accomplished by
the innumerable villi or tiny projections which stud the surface of
the mucous membrane and give it a velvety appearance. There are
also millions of small glands or follicles which secrete the intestinal
juice, an important aid to digestion. Beside the intestinal glands
we have already seen that the liver and pancreas empty their secre-
tion into the small intestine at its upper part.
The functions of the liver are many ; the most important are the
production and storage of sugar, the production of urea, and the
secretion of bile. The bile helps to emulsify fats, stimulates the in-
testinal muscle to contraction, acting as a laxative, and is. a natural
antiseptic preventing putrefaction of the intestinal contents. It is a
familiar fact that when bile is absent from the intestine, as in some
forms of jaundice, constipation and very offensive stools are apt to
The pancreatic juice digests all three classes of food, albuminates
starches and sugar, and fats.
Unlike the gastric juice, it is alkaline and incapable of acting ex-
cept in the presence of an alkaline reaction.
To digest foods outside of the body we now use pancreatin and
soda almost to the exclusion of pepsin and acid.
Under the combined influence of all these intestinal juices the
chyme is soon converted into a milky liquid known as chyle, and this
68 ANATOMY AND PHYSIOLOGY
is absorbed by both the capillaries of the intestinal tract, whence it
passes to the liver through the portal veins, and by the lymphatics or
lacteals, another system of vessels which, arising in the villi, passes
through a number of lymphatic glands situated in the mesentery and
known as the mesenteric glands, to reach a large duct known as the
thoracic duct, which passes up the left side of the spinal column and
empties into the left subclavian vein, just before its junction with the
left internal jugular.
The spleen has no direct part in digestion, but it does serve in-
directly by acting as a reservoir for the storage, in the intervals of
digestion, of the additional amount of blood needed during digestion.
Other important functions of the spleen are the production of leuco-
cytes, the destruction of erythrocytes, and the production of uric
Passing on down the small intestine, the intestinal contents become
more and more solid by the absorption of the liquid chyle, and this
process is continued in the large intestine until finally the indigestible
residue is cast out of the body as feces.
Some digestion and absorption do take place in the large in-
testine, as we know from what occurs when we use nutrient enemata,
but the action is not a powerful one, and it is safer to give the
When digestion is incomplete from any cause, putrefactive changes
may occur in the undigested portion of food and the poisons result-
ing therefrom may be absorbed, giving rise to fever, headache", and
other symptoms of auto-intoxication.
THE BLOOD AND THE CIRCULATORY SYSTEM
THE circulatory system includes the lymphatic system and the
The lymphatic system, or absorbent system (Fig. 31), includes the
lymphatic and lacteal vessels, and the lymphatic glands.
FIG. 31. Lymphatic System of Trunk, Genitals, and Upper Arm.
ANATOMY AND PHYSIOLOGY
The lymphatic vessels are found in all parts of the body, wherever
there are blood-vessels; they contain lymph, a colorless fluid like
water, except those of the intestine, which during digestion contain a
milky fluid, which gives to these particular lymphatics the name of
FIG. 32. Thoracic Duct.
lacteals. All over the body also are found lymphatic glands, varying
in size from a pin head to a small almond; all the lymph passes
through these glands before it reaches the blood by way of the
thoracic (Fig. 32) and lymphatic ducts. The lymphatic system has
an important function in connection with the elaboration of the blood,
THE BLOOD AND THE CIRCULATORY SYSTEM 71-
more and more blood cells appearing in the lymph as it passes
through successive chains of glands.
The glands also serve a very useful purpose in resisting the in-
vasion of the body by disease germs.
In the case of an infected ringer wound, for instance, one some-
times sees fine red lines running up the arm and the patient complains
of a kernel in the arm-pit ; the red lines are inflamed lymphatics and
the kernel is an inflamed gland ; again, in the case of a sore on the
penis the glands in the groin swell, constituting a bubo.
Certain groups of lymphatic glands are impor-
tant owing to their connection with special diseases.
A characteristic of syphilis is an enlargement of
the inguinal, epitrochlear, and post-cervical glands,
found respectively in the groin, just above and
behind the inner elbow, and at the junction of the
neck with the back of the head. FIG. 33. a, b, c,
The inguinal glands also become inflamed in other edge, e in^rouieaux!
i j- T-,I , , ., f r ,, crenated; e,f, white
venereal diseases, ihe glands in the front of the ceils,
neck become enlarged, cheesy, and sometimes suppurating in the
condition commonly called scrofula, really a tuberculous invasion
through the mouth.
The functions of the blood and blood-vascular system are to re-
ceive from the lungs and alimentary tract and to carry to all parts
of the body the materials necessary for its nutrition and proper
temperature and moisture, and to carry away to the excretory organs
the waste matters which if retained would prove poisonous. It has
also important functions in the protection of the body from the
invasion of the bacteria of disease.
The total quantity of blood is usually estimated at one-twelfth of
the weight of the body, or an average of about a gallon and a half.
The blood is red in color, bright red in the arteries, dark red in the
veins. It is composed of cells or corpuscles floating in a liquid, the
The cells are of two sorts, the red cells or erythrocytes and the
white cells or leucocytes (Fig. 33). The red cells are much the more
numerous, there being about five hundred times as many as there are
of the white. They are very small, about one-three-thousandth of an
inch in diameter, and, though red in mass, the individual cells are
72 ANATOMY AND PHYSIOLOGY
seen under the microscope to be light yellow in color. They are
round, flattened discs, like a copper cent, except that they are con-
cave on each side, and are largely composed of hemoglobin, a sub-
stance which has a great oxygen-carrying capacity.
The leucocytes are not flat like a cent, but spherical like a ball, a
little larger than the red cells, composed of protoplasm, and capable
of changing their own form and of making their way through the
unbroken walls of the blood-vessels.
The liquor sanguinis consists of serum and the elements of fibrin;
when bleeding occurs the fibrin at once forms and the blood coagu-
lates or clots; but for this property of the blood hemorrhages would
Serum, which is liquor sanguinis less fibrin, contains the principal
nourishing ingredients of blood albumin, fats, sugar, salts, and
In a general way the blood current may be likened to a river and
the cells to boats floating upon it ; the red cells are the freight boats
loaded with oxygen which they receive in the lungs and carry to all
parts of the body ; the white cells are the war ships, always on the
alert for an attack by disease germs ; when such an attack occurs the
leucocytes hurry to the invaded point and a battle ensues in which
there are killed and wounded on both sides ; the dead white cells,
when in large number, constitute pus or matter. The blood serum
itself not only carries nourishment to all parts of the body, but, com-
ing back, acts as a sewer, bringing away the waste products, both
liquid and gaseous.
In order to maintain a constant circulation of the blood, a com-
plete system exists, consisting of a constantly acting pump, the heart,
the arteries which carry the pure Hood to all parts of the body, the
capillaries from which the blood delivers its nutritive materials to
the tissues and takes on a load of waste products, and the veins which
return the impure blood to the right side of the heart ; this is the
systemic circulation and requires about a half a minute for the en-
tire trip; then there is a subsidiary system known as the pulmonary
circulation, whose arteries take the impure blood from the right side
of the heart to the lungs, in the capillaries of which it is purified,
losing carbonic acid and waste matters, taking on a load of oxygen,
and then passing through the pulmonary veins to the left side of the
heart for another trip through the systemic circulation (Fig. 34).
THE BLOOD AND THE CIRCULATORY SYSTEM 73
The heart is a conical hollow muscle, situated between the lungs
and behind the sternum and enclosed in a fibrous sack, the pericar-
dium (Fig. 35). It is about the size of a closed fist, its average
weight being three-fourths of a pound. The apex is found between
the fifth and sixth ribs, just inside of the nipple line. It is divided
FIG. 35. The Thoracic Organs, a, Right lung divided into three lobes, and b, left
lung into two lobes, their anterior margins thrown back to expose the deeper parts;
c, trachea, with its cartilaginous rings; d, right bronchial tube; e, ripht auricle, receiving
from above, /, the superior vena cava, which is formed by the junction of g, g, the right
and left innominate veins, and each of these by the confluence of h, h, i, i, the ju.eular
and subclavian of its own side; /, the right ventricle, giving issue to k, the pulmonary
artery, which divides into two branches, that for the right lung passing behind the other
great vessels; /, I, I, I, pulmonary veins, bringing oxygenated blood to m, the left auricle;
n, the left ventricle, from which the blood is carried to the organs and tissues by o, the
aorta; p, p, q, q, carotid and subclavian arteries, given off from the arch of the aorta.
by a vertical partition into two lateral halves which have no com-
munication with each other. Each of these lateral halves is further
subdivided by a horizontal constriction into two communicating
cavities, an auricle and a ventricle; the whole heart is lined by a
smooth membrane, the endocardium, and all its openings are pro-
tected by valves (Fig. 36).
The right is the venous side of the heart ; its auricle receives the
venous blood from the entire body through the superior and inferior
vena cava; when it is full it contracts and passes the blood into the
right ventricle, which in its turn contracts and sends the blood to
the lungs, whence it is returned arterialized to the left auricle, and
ANATOMY AND PHYSIOLOGY
from there to the left ventricle which forces it through the arteries to
all parts of the body. This contraction or beating of the heart takes
place about seventy-two times to the minute. The valve between
the auricle and ventricle on the left side is known as the mitral, that
on the right side as the tricuspid, while the valves which prevent
regurgitation from the aorta and pulmonary arteries are known as
the aortic and pulmonary, respectively.
The arteries are elastic,
muscular tubes, which stand
open when cut across, and
are without valves except at
their exit from the heart.
The elastic tissue in their
walls allows them to expand
when blood is forced in from
the heart, and by subsequent
contraction to maintain a uni-
form pressure between heart-
beats. It is this expansion,
caused by the heart forcing
more blood into the already
full arteries, which consti-
tutes the pulse. The mus-