cular tissue allows of a local
regulation of the circulation
under nervous influences such
as occur in blushing or the
FIG. 3 f . The Heart. pallor of f ear.
The arteries freely communicate with each other by the anasto-
mosis of small branches, so that when an artery becomes blocked
by a clot, or is tied, the blood goes around the obstruction by means
of the communication between the small branches given off on either
side and the collateral circulation is established. It is by reason of
the freedom of this collateral circulation that both ends of a cut
artery spurt, and but for it gangrene might ensue when an artery
By the constant giving off of branches the arteries become smaller
and smaller until they finally terminate in the capillaries.
GHT ; LE
LE I VENTRICLE
DIAGRAM TO SHOW THE COURSE OF THE BLOOD IN
PASSING FROM A GIVEN POINT THROUGH THE TWO
SETS OF CAPILLARIES TO THE STARTING POINT.
THE BLOOD AND THE CIRCULATORY SYSTEM 75
The capillaries, so called because of their resemblance to minute
hairs, though they are much smaller than the finest hairs, differ from
the arteries in being of a uniform size throughout, and in having only
a single thin celular coat through which the ultimate interchange of
materials takes place between the blood and tissues.
The smallest veins start from the capillaries and constantly join
each other, growing larger and larger, until finally all the venous
blood in the body enters the right side of the heart through the
superior and inferior vena cava. The pulmonary veins, unlike other
veins, return arterial blood from the lungs to the left auricle.
Veins differ from arteries in the following particulars: Veins:
The contained blood is dark red ; it flows in a continuous
stream without spurting ; it flows toward the heart. The
veins have thin walls so that they collapse when cut
across ; bleeding occurs only from the far end of the cut
vein, because the valves (Fig. 37) with which all veins
(except those of the rectum) are supplied prevent a
backward flow of blood from the near end. Many veins
are superficial and may be seen under the skin.
Arteries: The contained blood is bright red; it flows in waves,
and spurts from the vessel when cut; it flows away from the heart.
Arteries have thick walls and stand open when divided, like a piece
of hose; bleeding occurs from both ends, owing to the absence of
valves and the freedom of the collateral circulation. The large
arteries are deeply placed near the bone and are usually on the inner
or protected side of a limb. The circulation of the blood in the
arteries is effected by the pumping action of the heart. In the veins
the action of the heart is only one factor, the other two being pres-
sure of the muscles in exercise and the aspirating power of the chest
in inspiration. When the muscles contract they press on the thin-
walled veins, and, as the blood is prevented from going backward
by the valves, it must go toward the heart..
When any obstruction exists in the course of a vein it is apt to
become enlarged or varicose; such enlargements we see in the leg,
constituting varicose veins, in the scrotum, called varicocele, and
about the anus, called hemorrhoids or piles.
All the arterial blood leaves the left ventricle of the heart by means
of a large artery, called the aorta (Fig. 38) ; this vessel arches back-
76 ANATOMY AND PHYSIOLOGY
ward over the root of the lung, to the left side of the spinal column,
down which it passes to the fourth lumbar vertebra, where it divides
into the common iliacs. From the arch of the aorta are given off
three large vessels, the innominate, the left common carotid, and the
left subclavian; the innominate soon divides into the right common
carotid and right subclavian, so that at the root of the neck the two
sets of arteries are symmetrical. The common carotids on each side
pass up alongside the trachea, or windpipe, where they can be felt,
to the upper border of the thyroid cartilage, or "Adam's apple,'*,
where they are divided into the internal and external carotids. The
internal carotids supply the interior of the cranium; they lie just
behind the tonsils on the inside of the throat. The external carotids
supply the exterior of the cranium and face, and the tongue; the
front edge of the sterno-mastoid muscle is the guide to this artery;
the external carotid, or better, the common carotid, may be com-
pressed against the vertebral column. The facial, a branch of the
external carotid, curves over the lower jaw about an inch in front of
its angle and can be compressed there ; the temporal, another branch,
passes up just in front of the ear and divides into an anterior and
posterior temporal branch. The superior and inferior coronary
branches of the facial unite with those from the opposite side to
form a complete arch in each lip.
The subclavian artery passes across the first rib just behind the
clavicle, then beneath the clavicle to the axilla, where its name
changes to axillary ; in the hollow behind the clavicle the subclavian
can be felt and compressed against the rib. The axillary artery,
where it passes beyond the armpit, is called bracial ; the brachial
extends from the lower margin of the axilla down the inner and
anterior aspect of the arm, and terminates about a half inch below
and in front of the bend of the elbow, where it divides into the radial
and ulnar. The course of the brachial artery is roughly indicated
by the inner seam of the coat sleeve, or by a line drawn from the
armpit along the inner border of the biceps muscle to the front of
the elbow ; it may be compressed against the humerus.
The radial artery passes down the radial side of the arm to the
wrist, where it winds around the outer side and then passes forward
to the palm between the thumb and index finger ; the ulnar artery in
like manner passes down the ulnar or inner side of the arm and
divides into two branches which anastomose with two similar
THE BLOOD AND THE CIRCULATORY SYSTEM 77
branches from the radial, forming the superficial and deep palmer
arches. Both the radial and ulnar are deeply buried under the
muscles until just above the wrist where they become superficial;
it is at this point that the beating of the radial is felt for in taking
the pulse. The position of the palmar arches is important, because,
owing to the fact that they receive branches from both the radial
and ulnar arteries, bleeding from them is profuse and requires for
its control pressure on both vessels. The superficial palmar arch
is on a line with the lower border of the extended thumb, while the
deep palmar arch is a half inch higher up.
The digital arteries, which supply the fingers, are branches of the
palmar arches and pass along both sides of each finger.
In the thorax the aorta gives off the intercostals, which run along
the inner surface of the upper and lower borders of each of the ribs;
in the abdomen it gives off important branches to all the abdominal
viscera, and divides into the common iliacs. The common iliac on
each side passes downward and outward to the margin of the pelvis
where it divides into the external and internal iliac. The internal
iliac goes to the interior of the pelvis and supplies it together with its
viscera and the generative organs. The external iliac passes down-
ward and outward to the fold of the groin, where it enters the thigh
and becomes the femoral. The 'femoral artery commences at the
center of the groin and passes down the front and inside of the thigh
to the back of the knee, where it is known as the popliteal ; its course
may be shown by stretching a string from the center of the groin to
the back of the knee; just below the groin it may be compressed
against the head of the femur.
The popliteal artery extends from the termination of the femoral
to just below the knee where it divides into the anterior and posterior
tibial ; it is so tightly held down under fascia and tendons that it is
hardly accessible for compression. The anterior tibial passes for-
ward between the tibia and fibula to the front of the leg and then
down deeply beneath the muscles to the front of the ankle, where it
becomes the dorsalis pedis which is distributed to the back of the
foot. The posterior tibial gives off a large branch, the peroneal, and
then passes down the back of the leg beneath the deep muscles to
the inner ankle, whence it passes to the sole of the foot and divides
into two branches, the internal and external plantar, which supply
the toes with digital arteries having the same distribution as those of
78 ANATOMY AND PHYSIOLOGY
the fingers. Behind the inner ankle the posterior tibial may be felt
The veins may be divided into three sets, the pulmonary, the
systemic, and the portal.
The pulmonary veins differ from all others in that they convey
arterial blood from the lungs to the left side of the heart; conversely,
the pulmonary artery conveys venous blood from the right ventricle
of the lungs.
The systemic veins (Fig. 38) are arranged in two sets, deep and
superficial; the deep veins accompany their corresponding arteries,
each of the large arteries of the leg, forearm, and arm having two
veins; the deep veins communicate with the superficial set. The
superficial veins lie just under the skin where they can, in many
localities, be plainly seen; those of the lower extremity are the
internal saphenous, which starts on the top and inner side of the foot,
runs up the inside of the leg and thigh and terminates in the femoral
just below the groin, and the external saphenous starting in like man-
ner on the outer side of the foot and emptying into the popliteal
behind the knee.
Those of the upper extremity are the radial on the outer side, the
ulnar on the inner side, and the median in the middle ; opposite the
bend of the elbow the median splits into two veins, the one, known as
the median cephalic, joining with the radial to form the cephalic, and
the other, the median basilic, uniting with the ulnar to form the
basilic; the basilic and cephalic both empty into the axillary. The
median cephalic is the vein ordinarily opened in bleeding. The great
superficial vein of the neck is the external jugular, which passes
down from the angle of the jaw to the middle of the clavicle ; it may
be brought into view by pressing with the finger just above the mid-
dle of the clavicle.
The portal system is composed of four large veins which collect
the venous blood from the viscera of digestion. The trunk formed
by their union (vera porta) enters the liver and breaks up into cap~
illaries from which another set of veins, the hepatic veins, arise,
which terminate in the vena cava. This circulation is for the pur-
pose of subjecting the products of digestion contained in these veins
to the special action of the liver before they go into the general
FIG. 38. The Circulation, Venous and Arterial.
THE RESPIRATORY APPARATUS
THE respiratory apparatus consists of the larynx, trachea, bronchi,
and lungs ; the thyroid gland, which lies upon the trachea, may be
conveniently considered in this connection (Fig. 39).
The larynx, or Adam's apple, is the organ of voice, and is situated
in the middle line of the neck, where it may be felt and seen mov-
ing up and down in the act of swallowing. It lies between the
trachea and the base of the tongue, and its upper opening is closed
during swallowing by a cartilaginous flap called the epiglottis; when
the tongue is drawn well forward, especially if the patient gags, the
epiglottis may be seen as a white cartilage curving forward over
the root of the tongue. When one chokes in swallowing because
the food is said to have " gone the v/rong way," it means that the
epiglottis has failed to close efficiently the opening into the larynx,
and food has gotten in, causing coughing for its expulsion.
The larynx is composed externally of cartilage ; internally two
white fibrous bands stretch from front to rear, and are known as the
vocal cords; it is the vibration of these vocal cords that produces
The trachea or windpipe is a cartilaginous and membranous tube
which extends downward 'about four and one-half inches from the
larynx to its division into the two bronchi, one of which goes to
each lung. The cartilages of the trachea and bronchi are arranged
in rings, and serve the purpose of keeping the windpipe open. The
right bronchus is larger and shorter than the left, and foreign bodies
which get into the windpipe usually lodge in this bronchus.
The bronchi divide and subdivide and give off branches like a
tree, at the same time gradually losing their cartilages and getting
thinner and thinner until the little bronchioli terminate in a sack the
walls of which are studded with air cells, a terminal bronchus and
its air cells resembling a bunch of grapes.
The termination of the bronchi together with the air cells con-
stitutes the lung tissue proper.
When the larynx becomes obstructed by disease so that air cannot
ANATOMY AND PHYSIOLOGY
get into the lungs and death is otherwise imminent, a tube is intro-
duced into the larynx between the vocal cords, intubation, or an open-
ing is made into the trachea and a tube inserted there, tracheotomy.
The lungs are the essential organs of respiration ; they are com-
monly known as " lights," and with the heart between them fill the
entire chest cavity (Fig. 35). Each is covered by a smooth, shining
serous membrane which
also lines the chest
cavity and is called the
pleura. Ordinarily the
lungs are everywhere in
contact with the chest
walls, but when an open-
ing is made in the chest,
as by a shot or stab
wound, or when inflam-
mation of the pleura
occurs and fluid is
poured out, a space is
formed between the
lung and the chest wall,
known as the pleural
cavity (Fig. 40).
The right lung has
three lobes, the left lung
two, and each is com-
posed of bronchi, air
cells, and the divisions
and subdivisions of the pulmonary arteries and veins.
In the ultimate air cells the venous blood of the pulmonary arteries
circulating in the capillaries is brought in contact with the air in the
cells, and the interchange takes place which results in the blood
receiving a supply of oxygen and becoming arterial, while the air
becomes charged with carbonic oxide, waste organic matter, and
In inflammation of the lungg, pneumonia, these air cells become
filled with liquor sanguinis containing some red blood cells, so that
air can no longer enter and that portion of the lung is temporarily
useless. In laryngitis and bronchitis mucus is poured out into the
FIG. 39. The Larynx, Trachea, Right and Left Bron-
chus, and the Lungs. The latter have been cut open to
show the method of division and subdivision of the
THE RESPIRATORY APPARATUS
bronchi and coughed up, but the air cells are free; hence those
affections are much less serious.
Breathing or respiration consists in the alternate expansion and
contraction of the chest, by which air is drawn in and forced out ;
the drawing in is known as inspiration and the forcing out as expira-
tion. The number of these movements in health is about eighteen
to the minute. In ordi-
nary quiet respiration
the principal muscle
concerned is the dia-
phragm, which in its re-
laxed state is arched up-
ward into the cavity of
the chest'; in its con-
traction the muscle is
flattened out, largely in-
creasing the capacity of
the chest, so that the air
rushes in through the
larynx to fill the vacu-
um; inspiration com-
pleted, the diaphragm
relaxes, the chest walls
collapse, and expiration
occurs. When respira-
tion becomes more ac-
tive the intercostal
muscles, which raise the
ribs, come into play,
and when still more
effort is required all the
muscles attached to the
chest come into action, and even the nostrils are dilated to allow the
entrance of more air.
Ordinary outdoor air contains about twenty-one parts of oxygen,
seventy-nine parts of nitrogen, and four hundredth parts of carbonic
acid, or four parts in ten thousand.
The oxygen is the element of the air which is necessary to sustain
life; it serves the same purpose as it does in a fire; maintains the
FIG. 40. Chest showing Pleurae.
84 ANATOMY AND PHYSIOLOGY
combustion by which heat and force are produced. If you shut off
the supply of air (oxygen) to a furnace the fire goes out; if you shut
off the supply to the lungs life goes out. The nitrogen has no other
value than to dilute the oxygen.
When air is breathed it loses a portion of its oxygen, is raised in
temperature, and has added to it in the lungs carbonic acid, organic
matter, and the vapor of water; the amount of contained carbonic
acid is increased a hundred times, to about four per cent.
As the air in a confined space is breathed over and over again,
headache and drowsiness are experienced, and even death may result.
A notable instance of this character occurred in India in the year
1756, when one hundred and fifty-six British prisoners were confined
in a dungeon eighteen feet square; the next morning one hundred
and twenty-three of them were dead.
The causes of these results were formerly supposed to be de-
ficiency of oxygen, increase of carbonic acid, and organic matter.
Now we believe that the real causes are increased temperature and
humidity, and stagnation of the confined air ; just how these factors
act, we do not know, but experience has demonstrated that when
the air is kept in motion, and the temperature reduced, the unpleasant
symptoms do not occur.
The inflow of fresh air to take the place of that which has been
breathed is known as ventilation.
The heat which is produced in the body by the burning or oxida-
tion of carbon, the resulting carbonic acid escaping through the
lungs, would raise the temperature of the body too high were it not
that provision is made for its regulation. The evaporation of water
is the principal cooling agency, the evaporation taking place from
the lungs and skin; this is going on all the time, though the vapor
from the lungs is only visible in cold weather. So with the skin,
the water is only visible in hot weather, when so much escapes that
the unevaporated portion becomes visible as sweat or perspiration;
the harder we work, the more heat is produced, and the more
evaporation of water is required to reduce the body temperature.
If the skin stops action the body temperature rapidly rises, and we
have the condition of heat stroke, in which the hot, dry skin is a
THE EXCRETORY APPARATUS
WE have already seen that in all life processes waste products and
poisons are produced, which, if not gotten rid of, are finally fatal
even to the life which produced them. The yeast fungus growing in
sugar solution produces a poison, alcohol, which when it reaches a
certain proportion destroys the life of the yeast; so with the human
body, it produces very deadly poisons which must be thrown off if
the body would live, and the apparatus by which these poisons are
eliminated is known as the excretory apparatus. The- skin, lungs,
large intestine, and urinary apparatus all take part in excretion.
The excretory functions of the skin, lungs, and rectum have been
fully described elsewhere. It remains to give a description of the
urinary apparatus, whose practically sole function is excretion. It
consists of the kidneys which secrete the urine and the ureters which
convey it to the bladder, where it accumulates until it is convenient
to discharge it through the urethra.
The kidneys (Fig. 32), one on each side, are situated in the loins,
at the back of the abdomen, behind the peritoneum, on either side
of the spinal column, and just below the last rib. They are about
four inches long by two and a half inches wide, by one and an eighth
inches thick, and weigh about five ounces each. They are covered
by a fibrous capsule which may be stripped off, and consist of two
portions, a cortex and a medullary portion. The cortex is the
secreting part, while the medulla is largely an aggregation of urinary
tubules on their way to the pelvis of the kidney.
Each urinary tubule, after many twists and loops, terminates in a
little sack, in which is a bunch or tuft of tortuous capillaries; the
veins emerging from these capillaries are smaller than the arteries
that empty into them, so that the blood in passing through is sub-
jected to some degree of pressure, and under the pressure water
and salts escape from the vessels. Farther on down the tubule the
secreting epithelium with which the tubule is lined takes from the
ANATOMY AND PHYSIOLOGY
blood the urea and other waste products necessary to purify it and
complete the urine.
On the inner side of each kidney is a deep depression containing
a funnel-shaped sac, the pelvis, which receives the terminations of
the urinary tubules, and is itself the starting point of the ureters.
The ureters are two musculo-membranous tubes, about the size of
a goose quill, and sixteen inches long, extending from the pelvis of
the kidneys to the urinary bladder (Fig. 41).
When a stone formed in the pelvis of the kidney finds its way
into one of these ureters, in its passage to the bladder, it naturally
has a hard time in getting
through such a small canal,
and the result is the excruciat-
ing pain experienced in such
a condition which is known
as renal colic.
The bladder is a muscular
bag which serves as a reser-
voir for the urine and in a
moderately distended condi-
tion holds about a pint. When
empty or containing only a
small amount of urine it lies
wholly within the pelvis, and
behind the pubis ; when full
it rises into the abdomen and
can be felt and percussed
above the pubis. To deter-
mine whether the bladder is
full we tap on the finger
placed just above the pubis ; if we get a hollow sound we know that
it cannot be distended (Fig. 42).
As the bladder rises into the abdomen it leaves exposed in front
a small area not covered by the peritoneum and through which it can
be aspirated without opening the peritoneum. Likewise there is a
similar area behind, where the bladder rests on the rectum and
through which it can be reached. The neck of the bladder is em-
braced by the prostate gland which in old men becomes enlarged
and makes a bar to the passage of urine.
FIG. 41. Section of the Kidney. A, Cortex;
B, medulla; C, pelvis; D, ureter.
THE EXCRETORY APPARATUS
The urethra is eight or nine inches long and extends from the
neck of the bladder to the meatus: when the penis is held up that
portion of the urethra under the pubis describes a curve with the
concavity upward, hence the curved shape of catheters and sounds.
Urine is a watery solution of urea, uric acid, coloring matter, and
salts, mostly urates, phosphates, carbonates, and chlorides. The
FIG. 42. Section of Bladder and Urethra.
average man passes about fifteen hundred cubic centimeters or three
pints of urine a day, and this urine contains about fifty grammes or
one and one-half ounces of solids. Normal urine is yellowish in
color, acid in reaction, and has a specific gravity of from 1015 to
The urea is the most important constituent, a little more than
an ounce being excreted daily.
Healthy urine when passed is ordinarily clear, but it may quickly
become cloudy and a sediment form without indicating disease. If
such cloudiness disappears when the urine is heated it is due to
88 ANATOMY AND PHYSIOLOGY
urates; if the cloudiness disappears on the addition of a few drops
of acid it is due to phosphates.
Among abnormal constituents of the urine, indicating disease, are
albumin, sugar, bile, blood, and pus.
Just above the kidney on each side is a small triangular ductless
gland known as the suprarenal gland. It has nothing to do with the
excretion of urine but is considered here for convenience. That
these little glands add something important to the blood is shown
by the fact that their removal in animals is quickly followed by
death, and that their diseased condition in man is the cause of a
fatal malady known as Addis on' s disease. Their function appears
to be to sustain muscular tone, especially in the blood-vessels, and a
substance known as adrenalin has been isolated from them which
has a very powerful effect in that direction.
EMERGENCIES, CONTUSIONS, AND WOUNDS