ficially. It divides into four parts for terminal phalanges
of the four lesser toes.
Tibialis Posticus, beneath the two long flexors.
Origin, posterior surface of the interosseous membrane,
outer part of the posterior surface of the tibia below
the oblique line of the middle of the bone, whole inner
surface of the fibula, and from the aponeurosis over it.
Tendon along the inner border of the muscle, free at
the level of the lower tibiofibular articulation, passes
behind the inner malleolus, inserted into the tuberosity
of the scaphoid, with offsets to the three cuneiform,
to cuboid, to bases of the second, third, and fourth
metatarsals, and to the transverse tarsal ligament and
flexor longus hallucis tendon, and sends a thin process
back to the sustentaculum tali of the os calcis.
Flexor Longus Hallucis. Origin, lower two-thirds of
the posterior surface of the fibula, septum between it
and the peronei ; aponeurosis common to it and flexor
longus digitorum. Tendon at the posterior surface
of the muscle traverses groove on the back of the
astragalus and under surface of the sustentaculum,
gives slip to the flexor longus digitorum in the sole
of the foot, and proceeds to the base of the terminal
phalanx of the great toe.
Muscles of the Foot
The Dorsal Region (Instep). Extensor Brevis Digi-
torum Pedis. Arises from forepart and upper and outer
surface of the os calcis, in front of the groove for the
peroneus brevis tendon, and from the anterior ligament
of the ankle. The tendon has several vertical leaflets
from which muscular fibers arise, dividing into three
bellies which unite with the outer border of the long
extensors for the second, third, and fourth toes.
The Plantar Region (Sole). THE CENTRAL GROUP.
Flexor Brevis Digitorum and Flexor Accessorius Lum-
bricales. Four in number. Origin, at points of division
MUSCLES AND FASCIA OF LOWER EXTREMITY 171
of the flexor longus digitorum tendon, each attached
to two tendons, except the most internal one; they pass
to the inner side of the four outer toes; inserted into
the bases of the first phalanges.
THE INTERNAL GROUP. Abductor Hallucis, flexor
brevis hallucis, and adductor hallucis (oblique trans-
verse portions).
THE EXTERNAL GROUP. Abductor Minimi Digiti,
and flexor brevis minimi digiti.
Actions. Popliteus flexes the knee and rotates the
leg inward, pulls on the capsule of the joint, and keeps
the popliteal bursa open. The dorsum of the foot
and anterior surface of the leg is the extensor surface;
the opposite side is the flexor surface, so that raising
the foot toward the front of the leg is really extension,
and depressing it is flexion; it is customary to apply
reverse terms to these acts.
Gastrocnemius flexes the knee, extends the ankle,
combines with the soleus, and lifts the heel or raises
the body on toes.
Tibialis anticus and peroneus tertius flex the ankle;
the former rotates inward, adducts, raises the first
metatarsal bone.
Tibialis posticus, peroneus longus and brevis are
extensors of the ankle-joint. Tibialis posticus and
flexors of the toes rotate the foot in. The three peronei
and extensors of the toes rotate outward.
Peroneus longus strengthens the transverse arch, lifts
the outer border of the foot in walking, extends the
foot, depresses the first metatarsal, abducts the fore-
foot, rotates outward.
Flexors and extensors of the toes, interossei, and
lumbricales act as do the corresponding muscles of the
hand.
Flexor accessorius modifies the action of the flexor
longus digitorum, as those tendons cannot enter the
foot in a straight line.
The extensor brevis digitorum does the same for the
172 MUSCLE TISSUE
extensor coimiiunis, though here they are not so much
needed, and their function is not so evident.
Extensors of the foot slightly rotate inward ; flexors of
the foot slightly rotate outward; plantaris indirectly
pulls up the capsule of the ankle-joint and slightly aids
the gastrocnemius.
Flexors of the foot. Extensors of the foot.
Tibialis anticus. Tendo Achillis.
Extensor communis digitorum. Peroneus longus and brevis.
Extensor proprius hallucis. Tibialis posticus.
Peroneus tertius. Flexor longus digitorum and
hallucis.
Adduction. Abduction.
Tibialis posticus (strongly). Peroneus brevis.
Tendo Achillis (weakly) . Peroneus longus.
Perhaps tendons behind the
inner malleolus, perhaps
the tibialis anticus.
Rotation in. Rotation out.
Tibialis anticus (strongly). Peroneus longus.
Tendo Achillis. Extensor communis digitorum.
Peroneus tertius.
The Interosseous Muscles. Interossei, as in the hand,
are seven in number, four dorsal and three plantar.
The dorsal project downward as low as the plantar,
and alternate with them. Only one muscle in the
first space, two in the others. The second phalanges
are their centre of insertion.
QUESTIONS
1. Name the three varieties of muscle tissue.
2. What does the sarcoplasm represent in muscle tissue?
3. Does the sarcoplasm possess the quality of contractility?
4. What do you understand by a skeletal muscle?
5 What forms the fibers in a muscle? The primary bundles?
Secondary?
6. What is the function of the epimysium? Perimysium? Endo-
mysium?
7. Where are voluntary striated muscles found in the body?
Involuntary non-striated?
MUSCLES AND FASCIA OF LOWER EXTREMITY 173
8. Where is involuntary striated muscle found?
9. What influences the consistency of a muscle?
10. What effect do irritating stimuli have upon muscles?
11. What stimulus causes muscle to contract in the living body?
12. Name some of the artificial and experimental stimuli for
muscles.
13. What is the function of a tendon? An aponeurosis?
14. What structure of bones receives the attachment of muscles?
15. Give the names applied to the parts of a muscle.
16. What do you understand by the origin of a muscle? Insertion?
17. Do most muscles act from either their origin or insertion?
18. How do muscles derive their names in the living body?
19. What variety of tissue forms tendons? Aponeuroses?
20. What are tendons attached to?
21. With which shaped muscles are aponeuroses usually found?
22. Where is fascia usually found?.
23. In the description of a muscle what must be included?
24. Name the muscles of mastication.
25. What muscles flex the forearm upon the arm?
26. Give action of the latissimus dorsi muscle.
27. What muscles fill up the intercostal spaces of the thorax?
28. Name the muscles which flex the fingers. Extend.
29. What muscles form the thenar eminence of the hand? Hypo-
thenar?
30. Name the musculomembranous structure which separates the
thorax and abdomen.
31. Give the origin and insertion of the following muscles: Biceps
(arm). Sartorius. Supinator longus or brachioradialis. Tibialis
anticus. Flexor longus hallucis. Rectus femoris. Palmaris longus.
32. Name the muscles which form in a general way the anterior
abdominal wall.
33. What muscle surrounds the eye and gives it function?
34. Name the muscles which adduct the thigh.
35. What muscle covers the shoulder-joint on its outer side?
36. Give a brief description of the scalp. Of the fascia of the palm
of the hand.
CHAPTER VIII
THE DESCRIPTION OF THE ANATOMY AND
PHYSIOLOGY OF THE CIRCULATORY
APPARATUS
THE circulatory apparatus consists of the heart,
covered by the pericardium, the arteries, veins, and
capillaries, and circulating fluid the blood.
THE PERICARDIUM
The pericardium is a serofibrous membrane which
invests the heart and the great vessels at their origin
for about two inches. The pericardium consists of a
fibrous and serous layer, between which is a small
amount of serous fluid, preventing friction, as at
each rhythmic contraction of the heart these layers
rub against each other. The serous layer (epicar-
dium) invests the heart muscle and is reflected to
the fibrous layer.
THE HEART
The heart is a hollow muscular organ situated in
the thorax between the right and left lobes of the
lungs, enclosed by the pericardial sac.
It lies obliquely, the base being directed upward,
backward, and toward the right, its position corre-
sponding to the surface of the chest wall extends
from the fifth to the eighth thoracic vertebra. The
apex looks downward, forward, and to the left, its
THE HEART 175
impulse against the chest wall being felt in the fifth
interspace on the left side, about 3| inches from the
middle of the sternum. The posterior or postero-
inferior surface is flat, formed chiefly by the wall of
the left ventricle, and rests on the diaphragm; its
anterior or anterosuperior surface is convex, formed
chiefly by the wall of the right ventricle, but also
partly by the left, and is overlapped by the lungs,
except in the central part. The borders of the heart
are right and left, the former is long and thin, the
left shorter and thicker. The length of the heart is
about 5 inches, the greatest breadth 3J inches; its
thickness about 2J inches. Its weight is approxi-
mately 10 to 12 ounces in the male, 8 to 10 ounces in
the female, and these increase with age.
Externally its surface presents a deep transverse
groove, auriculoventricular, which marks an upper
auricular and lower ventricular portion; this latter
part presents a longitudinal furrow on the front and
the back, the former being somewhat to the left, the
latter to the right, marking off the right and left
ventricles (interventricular groove).
The heart contains four chambers. They are divided
by a longitudinal partition or septum into a right and
left part, and these in turn are subdivided into an
auricle and a ventricle by a transverse partition,
which is perforated on each side by an opening, called
the auriculoventricular, connecting the auricle and
ventricle
The Cavities of the Heart. The inner surface of
the heart muscle (myocardium) is lined throughout
by a thin layer of membrane called the endocardium.
It is continuous with the lining membrane of the
great bloodvessels opening into the heart cavities,
and helps to form the, various valves by a process,,
whereby the membrane is thrown into folds. The
endocardium consists of a flattened layer of endothelial
cells resting on a membrane formed of subendothelial
176
THE CIRCULATORY APPARATUS
(fibro-elastic) tissue. On opening the heart the
following structures can be seen within its cavity:
The Right Auricle. This is larger than the left, its
wall being about one line in thickness and its capacity
two ounces. .Within the auricle the following parts
present themselves for examination:
FIG. 71
Front view of the thorax, showing relation of the heart and its valves,
lungs, etc., to the ribs and sternum. P, pulmonary orifice; Ao, aortic orifice;
M, left auriculoventricular orifice; Tr, right auriculoventricular orifice.
The orifice of the superior vena'cava, looking downward
and forward. The orifice of the inferior vena cava, at
the lowest part, near the septum, looking upward
THE HEART
111
and inward. Between the two caval openings a
projection, the tubercle of Lower. The opening of the
coronary sinus, between the inferior cava and the
auriculoventricular opening, and protected by the fold
of endocardium forming the coronary valve. Numer-
FIG. 72
Foramina
Thcbcsii
Tubercle
of Loi.
JlriMc ]inKfd through
right aurirttloiriitHcular opening.
The right auricle and ventricle laid open, the anterior walls of both being
removed. (Gray.)
ous small openings (foramina Thebesii) of the small
veins of the heart. The auriculoventricular opening,
between the auricle and ventricle. The Eustachian
valve, between the front of the inferior vena cava
12
178 THE CIRCULATORY APPARATUS
and the auriculoventricular orifice. It is semilunar
in form, the free concave margin sending one cornu
to join the front of the annulus ovalis and the other to
the auricular wall. The fossa ovalis, at the back of the
septum, in the situation of the fetal foramen ovale,
its prominent margin being known as the annulus
ovalis. The musculi pectinati, small elevated columns
which traverse the appendix and the adjacent part
of the sinus.
The Right Ventricle. This is pyramidal, and extends
nearly to the apex of the heart. It is bounded inter-
nally by the convex surface of the wall of the ven-
tricles, and prolonged above and internally into a
pouch, the infundibulum, or conus arteriosus, from
which springs the pulmonary artery. Its cavity has
a capacity of three ounces. On opening the ventricle
the following parts are presented for examination:
The auriculoventricular orifice, oval in form, and
placed near the right side of the heart. Around its
circumference is a fibrous ring, and it is guarded by
the tricuspid valve. The opening of the pulmonary
artery, circular in form, at the summit of the conus
arteriosus, near the septum; is guarded by the pul-
monary valves (semilunar) . The tricuspid valve consists
of three triangular flaps formed of fibrous tissue covered
by endocardium. They are continuous with one
another at their bases, and their free margins and
ventricular surfaces give attachment to the chordae
tendinese. Their central part is thick and strong, the
lateral margins thinner and flexible. The chorda
tendinece are attached as follows: several to the attached
margin of each flap, blending with the fibrous ring;
several to the strong central part; and the finest and
most numerous to the margins of each curtain. The
columncB carneoe are projecting bundles of muscular
substance found all over the ventricular wall excepting
the conus arteriosus. They afford attachment for
the papillary muscles. The three semilunar valves
THE HEART 179
guard the pulmonary orifice. They are semicircular,
their free margins being thick and tendinous, and
presenting at the middle a small fibrous nodule, the
corpus Arantii. On each side of this body, just behind
the free margin, the valve presents a small thinned-
out interval, and when the valves are closed
during diastole these valves are in contact, and so
also are the three nodules. These latter prevent
any leakage from the triangular space which would
otherwise be left. At the commencement of the
pulmonary artery are three pouches, the sinuses of
Valsaha, placed one behind each valve. They resemble
those of the aorta, but are smaller.
The Left Auricle. This is smaller and thicker walled
than the right, and consists, like the right, of a sinus
and an appendix. The latter overlaps the pulmonary
artery. Within it presents the following features
of interest:
The orifices of the pulmonary veins, opening two
into the right and two into the left side (sometimes
only three are seen); the auriculoventricular orifice;
and a few musculi pectin ati on the inner side of the
appendix.
The Left Ventricle. This is longer than the right, and
forms the apex of the heart. Its walls are three times
as thick as those of the right. Within it presents for
examination :
The auriculoventricular orifice, which is smaller than
the right and guarded by the mitral or bicuspid
valve; and the aortic opening, in front and to the
right of the preceding, guarded by the semilunar
valves. The mitral valve is attached, like the tricuspid,
on the right side. It consists of two curtains which
are larger and thicker than those of the tricuspid,
and of two smaller segments, one at each angle of
junction of the former. They are furnished with
chordae tendinese. The aortic semilunar valves are
similar to but larger and stronger than the pulmonary
180 THE CIRCULATORY APPARATUS
valves. Columnce carnece are found in the right
ventricle, and the musculi papillares are very large;
one is attached to the anterior wall, the other to the
posterior.
See Fig. 71 for relation of the valves and orifices of
the heart to the chest wall.
The muscle fibers of the heart are attached to car-
tilaginous rings which surround the auriculoventricular
and arterial orifices.
Nerves. (See pages 121, 383.)
THE CIRCULATION OF THE BLOOD
The heart is the pump which propels the blood,
aided by the elasticity of the arteries, veins, and
connecting capillaries throughout the body. Without
the rhythmical contraction of the heart muscle, life
cannot be maintained. The blood courses through
the cavities of the heart as follows. Allowing that
the heart has emptied its chambers, this blood is
returned to the heart as venous blood through the
superior and inferior vena cavse which open into the
right auricle, from which it passes to the right ven-
tricle through the auriculoventricular opening. The
blood now is forced into the pulmonary artery and
its branches to the pulmonary capillaries in the lungs,
where the blood, coming in contact with the air we
breathe, by a process of gaseous exchange, gives up
the carbon dioxide to the lungs, and absorbs oxygen,
becoming bluish red or scarlet in color. This new or
arterialized blood is carried back by the pulmonary
veins to the left auricle of the heart, flows through the
left auriculoventricular opening into the left ventricle
and thence through the aorta to the small arteries
coursing along until the capillaries are reached in
every part of the body, when by the same gaseous
exchange as we said occurred in the lungs, the blood
gives up its oxygen to the tissues and absorbs the
PLATE III
Pul m on ctry Capillaries
Diagram to Show the Course of the Circulation
of the Blood.
This diagram does not show that the liver also receives blood
through the hepatic artery.
THE CIRCULATION OF THE BLOOD 181
carbon dioxide from them, and is changed from a
scarlet to a bluish red color. The same venous return
of the blood occurs to the right auricle and the cycle
is repeated. It must be remembered that while the
venae cavse are filling the right auricle, the pulmonary
veins are at the same instant pouring their contents
into the left auricle.
The blood is moved through the heart and blood-
vessels by a continuous, rhythmic, and automatic
contraction and relaxation of the heart muscle due
to an inherent power possessed by the heart of con-
verting potential energy stored up during the period
of rest into kinetic energy, i. e.,- heat and mechanic
motion. The rhythmic contraction wave of the
heart is carried on by means of a thin and distinct
bundle of muscle fibers the bundle of His or atrioven-
tricular. It commences in the right auricle near the
orifice of the Eustachian valve and passes to the wall
between the ventricles to end in the papillary muscles
of the ventricles. Disease or injury to these fibers
causes an interference with the muscular contraction
which begins in the auricle and extends to the ventricles.
This leads to a condition which arises as a result of the
auricle continuing to contract, and forces the blood into
the ventricles, allowing the blood to be continuously
pumped, while the ventricle not responding permits the
blood to collect, due to its inability to contract. This
condition is called Adams-Stokes sign or heart-block and
is fatal. When any portion of the heart contracts it
is called the systole, and relaxation, the diastole. The
heart having two cavities on each side, when their
walls contract and relax in succession we speak of
an auricular systole and diastole, and a ventricular
systole and diastole.
The contraction systole of the heart muscle starts
as a wave in the great veins and then passes to the
base of the heart in both auricles, and extends rapidly
over the ventricles to the apex; during this period
182 THE CIRCULATORY APPARATUS
the auricles and ventricles empty their cavities of
blood into the pulmonary and arterial systems from
the right and left sides of the heart respectively.
Following this contraction wave is a pause or relaxa-
tion of the muscle the diastole during which time
the blood rapidly flows into the auricles and ven-
tricles, and at the end of the relaxation or diastole
there is a period of rest, during which time the auricles
and ventricles, or, in fact, the whole heart, is quietly
filling with more blood, when the phenomenon is
resumed.
The Part Played by the Heart Muscle and Valves
during the Course of the Blood through the Chambers
of the Heart. We will start by allowing that the
contraction or systole of the ventricle has occurred.
Instantly the column of blood forced into the aorta
and pulmonary artery, by filling the sinuses of Val-
salva, forces the margins of the semilunar valves
together and prevents the return of the blood to the
ventricles from the aorta and pulmonary artery;
while the ventricle contraction or systole was emptying
its chambers, the auricles were filling from the vense
cavse and pulmonary veins, and this blood was rapidly
passed into the ventricles during the relaxation or
diastole, while a new supply has taken its place in
the auricles, the ventricles becoming distended with
more blood (during the period of rest) force upward
the tricuspid and mitral valves, gradually closing the
auriculoventricular openings. Suddenly the auricles
contract or begin their systole, and more blood is
forced into the ventricles, the valves close; immedi-
ately the ventricular systole or contraction takes
place, the, blood not being able to pass back into the
auricles owing to the closure of the auriculoventricular
openings, is forced into the aorta and pulmonary
artery, when the semilunar valves are flattened against
the walls by the pressure from the blood in the ven-
tricles. Now the ventricular systole is completed, the
THE CIRCULATION OF THE BLOOD 183
semilunar valves are instantly closed to prevent a
return of blood to the ventricles from the aorta and
pulmonary artery; the period of rest occurs, following
the emptying of the ventricles, and the cycle is repeated.
The Cardiac Cycle or Revolution. This has been
shown above to consist of (1) an auricular contraction,
(2) ventricular contraction, (3) the period of repose,
during which time the auricles and ventricles are at
rest. There are 72 cycles per minute made by the
heart of a healthy adult, and the average duration of
each cycle is about eight-tenths of a second, divided
as follows:
Auricular systole T V Auricular diastole 7%
Ventricular systole -*$ Ventricular diastole T 5 <y
Common pause f l d
The Heart-beats. In a healthy adult the pulsations
or cardiac cycles are 72 per minute; in the fetus, 140 per
minute; during the first year of life it decreases to
128 per minute; during the third year to 95 per minute;
from the eighth to the fourteenth year, 84 per minute.
It is more rapid in the female, averaging 8 to 10
more beats per minute. The pulse of a person lying
down is a few beats less than when sitting or stand-
ing. Exercise and digestion temporarily increase the
number of beats.
The Heart Sounds. On placing the ear or the
stethoscope to the chest wall overlying the heart, or
in the fifth intercostal space, 3J inches from the
middle of the sternum, two sounds resembling the
pronouncing of the syllables lubb-dupp, lubb-dupp,
will be heard. They accompany each pulsation of
the heart and are called the first and second sounds;
the former is dull and long, and occurs with the
cardiac systole or contraction; the latter is short and
clear and occurs at the commencement of diastole or
relaxation of the heart muscle. The cause of the
first sound is supposed to be due to the contraction of
184 THE CIRCULATORY APPARATUS
the muscular walls of the ventricles, the gradual
closure and vibrations of the mitral and tricuspid
valves, and the sudden pressure of the apex against
the chest wall. The second sound is supposed to be
due to the sudden closure and vibrations of the semi-
lunar valves in the aorta and pulmonary artery,
following the ventricular systole or contraction; also
the sound is added to by the whirling of the column
of blood against those closed valves at the beginning
of diastole or relaxation of the ventricles.
The Fetal Circulation. The fetus is nourished by
the blood from the placenta (afterbirth). The blood
is conveyed from the placenta to the fetus by the
umbilical vein. This vein enters the umbilicus and
passes upward along the upper free margin of the
suspensory ligament of the liver to the under surface
of the liver. The blood after nourishing the organ
by two or three branches, finally reaches the inferior
vena cava by way of the hepatic veins, and the ductus
venosus, which runs from the transverse fissure of
the liver to open into the hepatic veins just before
they open into the inferior vena cava. The superior