weight of the body from the leg. It articulates with
THE BONES OF THE LOWER EXTREMITY 103
four bones the tibia above and internally; the fibula
externally; os calcis below, and scaphoid in front. It
belongs to the irregular group of bones.
FIG. 51
^ktetarsal foxes.
Jj/f. cu/iifform
Hid. cutuef&rtn
/>/. crmifforffi ...
Wavicalar baste.
Astragalus
Tufarosity of fifth
7/wtatatyal fiwtc
Cuboid bone
.. Os Catcis
Bones of the right foot.
104 OSTEOLOGY
The Metatarsal Bones. The metatarsal bones are
five in number; they articulate with the tarsal bones
behind and the corresponding phalanges (1 to 5) in
front. They present for examination a shaft, a proximal
extremity, or a base ; a distal extremity or head.
The first bone is the shortest and thickest, the
second the largest, and the fifth the thinnest. Each
bone has a nutrient canal on its plantar surface.
The Phalanges of the Foot (Bones of the Toes). The
phalanges have the same arrangement and shape as
those of the fingers, except that they are longer and
larger. They are fourteen in number for each foot,
allowing three (1st, 2d, and 3d) for the second, third,
fourth and fifth toes; the big toe has two (1st and 2d).
The first or proximal phalanges articulate with the
corresponding metatarsal bone above and the second
phalanges below. The second phalanges articulate
with the corresponding first phalanges above and third
below. The last or distal phalanges articulate with
the corresponding second phalanges above.
QUESTIONS
1. How many bones enter into the formation of the body skeleton?
2. Name in a general way the bones which are included under
the axial skeleton. Appendicular skeleton.
3. How many auditory ossicles are there?
4. Give the classification of bones?
5. Name the long bones. Short bones. Flat bones. Irregular
bones.
6. Give an example of an articular eminence. Articular depres-
sion.
7 Name two varieties of non-articular eminences. Non-articular
depressions.
8. Give the constituents of dried bone.
9. Do the mineral salts predominate in the bones of children or
adults?
10. Why are the bones of children more elastic than those of
adults?
11. What is the periosteum of a bone?
12. Give the two classes of bone based on their composition?
13. Wha do you understand by the medulla of a bone? Give
contents.
QUESTIONS 105
14. Name the two varieties of marrow and what makes the
difference in color?
15. Give the function of bone-marrow.
16. How are bones nourished during life?
17. Name the number of bones forming the cranium. The face.
18. Name the unpaired bones of the cranium. The paired bones.
19. Name the unpaired bones of the face. The paired.
20. Give the bones bounding the orbital cavity.
21. What bones and cartilage form the septum of the nasal cavity?
22. How many fontanelles are there in the skull of an infant?
23. Until what age do they remain membranous before ossifica-
tion generally occurs?
24. How many separate vertebra are there?
25. Give the subdivisions of vertebra, as regards their location?
26. Name the movable vertebra. Immovable.
27. Mention the general characteristics of a typical vertebra.
28. Give the contents of the spinal canal.
29. Name the structures that pass through the upper opening
of the thorax. The lower opening.
30. What structure separates the thoracic cavity from the abdomi-
nal cavity?
31. What openings are found in the diaphragm and what passes
through each one?
32. Differentiate the female from the male thorax.
33. How many pairs of ribs are there?
34. Give the classification of ribs as to arrangement.
35. What do you understand by the true or vertebrosternal ribs?
The false or asternal ribs? Vertebrochondral ribs? Floating or
vertebral ribs?
36. W T hat are the functions of the costal cartilages?^
37. What bones form the shoulder girdle?
38. Name the bones of arm. Forearm. W T rist. Palm. Fingers.
39. Name the bones which form the pelvis.
40. Differentiate the true from the false pelvis.
41. Name the thigh bone. Bones of leg. Instep.
42. How many metacarpal bones are there? Phalanges?
43. What bones does the humerus articulate? The femur? The
Tibia? The ulna? The radius?
CHAPTER VI
ARTICULATIONS OR JOINTS
The General Structure of Joints. The bones of
the human body are held in movable, immovable, or
mixed relations with each other, depending upon the
degree of action required in the various movements,
functions, and positions assumed by the body. The
parts entering into the formation of these relations
taking place between bones, comprise a joint or artic-
ulation they are: bones, ligaments, cartilage, and a
synovial membrane.
Bones. The articular portions of bones are enlarged
to form a joint of suitable size, so that muscles passing
over the joint can act at a greater angle. The layer
of bone beneath the cartilage entering into a joint is
a compact articular lamella.
Cartilage. There are three varieties of cartilage-
hyaline, fibrocartilage, and yellow elastic (see page
51 for description of cartilage). The fibrocartilage
and hyalin are utilized in the structure of a joint;
the former where slight movement and great strength
are required as between vertebrae and the pubic bones
of the pelvis; the latter where freedom of movement
is essential, and a greater surface for general con-
venience of mutual connection is demanded, as in the
shoulder- and hip-joints, etc.
Ligaments. The ligaments connecting the immov-
able joints, such as the bones of the skull, consist of
a thin layer of fibrous membrane called sutural liga-
ments, and have a layer of cartilage interposed as
the bones of the base of the skull.
THE GENERAL STRUCTURE OF JOINTS 107
The ligaments are mainly white fibrous tissue of
various forms, serving to connect the articular surfaces
of bones; and the fibers, usually arranged in parallel
rows, or closely interlaced with one another, present
a white, shining, silvery surface, when seen in the
recent state. Some ligaments contain yellow elastic
tissue, which is present in the ligamentum subflava
connecting the adjacent arches of the vertebrae in man.
The Synovial Membrane. This is a thin, delicate
serous membrane arranged like a short white tube,
attached by its open ends to the margins of the artic-
ular cartilages and covering the inner surfaces of the
various ligaments, so that along with the cartilage it
completely encloses the joint cavity. It secretes a
viscid, thick fluid like the white of an egg hence its
term synovia which acts as a lubricant to the joint.
The membrane is composed of a layer of endothelial
cells resting upon a thin layer of fibro-elastic (sub-
endothelial) tissue. There are three varieties of sy no-
vial membranes articular, bursal, and vaginal.
The articular is found in a freely movable joint. It
lines the capsule and the non-articular intracapsular
portion of the bones which enter into the formation of
a joint. Some of these membranes contain fat, acting
as a cushion between the articular surfaces.
The bursse are mucous between the skin and bone
(subcutaneous synovial bursae) ; and synovial between
muscles, tendons, and bone (subtendinous synovial
bursse) .
Vaginal synovial membranes are sheaths for tendons.
They prevent friction and with their secretion lubricate
the tendons as they move within the sheath in carry-
ing on their action.
Some joints have tendons passing through their
cavities (the knee-joint has the popliteus muscle and
the shoulder-joint the biceps) and they are always
enclosed by the synovial membrane within the joint,
to prevent friction and facilitate action.
108
ARTICULATIONS OR JOINTS
a
JS
-: I
1 i
a '8
J'gS
SH
l-a*
fel- 2
CO
'& ^ '? 8
|S 5^
S rs 3 03
_fj ^ 2 O
T3 2 >>
. T3 e a .-
1ilii
+J 5) 5 "H
^^ s
-:*!!!
PJJ3I
&^r-aa
THE CLASSIFICATION OF JOINTS 109
The Classification of Joints. All joints of the body
are classified under three main groups immovable
articulation (synarthrosis), slightly movable or mixed
articulation (amphiarthros), movable articulation (diar-
throsis).
FIG. 52
Occipito-axial and atlanto-axial ligaments. Posterior view, obtained by
removing the arches of the vertebrae and the posterior part of the skull.
(Gray.)
Synarthrosis or Immovable Joint. Under this classi-
fication are included all the articulations in which
the surfaces of the bones are in almost direct contact,
being fastened together by an intervening mass of
connective tissue, and in which there is no joint cavity
and scarcely any motion. Examples: joints between
the bones of the skull and face, excepting those of the
mandible.
Amphiarthros or Mixed Joint. In this variety there
is only a slight amount of motion. There are two
varieties symphysis, as the symphysis pubes and
110
ARTICULATIONS OR JOINTS
bodies of vertebrae in which the articulating osseous
surfaces are connected by a broad flattened disk of
fibrocartilage which is firmly attached to both bases
in the articulation. Syndesmosis, in this variety there
is slight motion and the bony surfaces are held in rela-
tion by an interosseous ligament. Example: inferior
tibiofibular articulation (between tibia and fibula).
FIG. 53
Temporomandibular articulation. (Gray.)
Diarthrosis or Movable Joint. Under this variety
are included the greater number of the joints of the
body, characterized by their freedom of movement.
These joints are formed by the bringing together of
the articular surfaces of two bones, covered by hyaline
THE CLASSIFICATION OF JOINTS
111
cartilage, and held together by ligaments with a lining
synovial membrane.
The Kinds of Movement Admitted in Joints.
These are divided into gliding, angular, circumduction,
and rotation. They are often combined, and it is sel-
dom that one distinct kind of motion is seen in any
certain joint.
FIG. 54
Temporomandibular articulation. Internal view. (Gray.)
Gliding Movement. This is common to all movable
joints, but in the articulations of the wrist and foot
it is the only motion permitted. It consists of one
surface of a bone gliding over an adjacent bone without
any angular or rotatory movement. The sliding of a
bone over a wide range of surface, as is seen in the
patella (knee-cap) over the condyles of the femur, is
called coaptation.
112
ARTICULATIONS OR JOINTS
Angular Movement. This is seen only in the joints
of long bones, whereby the angle between the two bones
is either increased or diminished. It is expressed in
Fia. 55
The left shoulder-joint, scapuloclavicular articulations, and proper ligaments
of the scapula. (Gray.)
four ways, as follows: bending or flexion to bend the
arm or leg forward or backward, etc. ; straightening or
extension to straighten the legs and thighs as in stand-
THE CLASSIFICATIONS OF JOINTS
113
ing, the arms, fingers, etc.; adduction to move a limb
toward the middle line of the body or extremity;
FIG. 56
Left elbow-joint, showing anterior and internal ligaments.
abduction to move it away from the middle line of the
body or extremity. When speaking of adduction or
114
ARTICULATIONS OR JOINTS
abduction of the fingers or toes, the second finger of the
hand and second toe are taken as the middle line and
not the middle of the body.
FIG. 57
Right hip-joint, from in front. (Spalteholz.)
Circumduction. This is the limited degree of motion
which takes place between the head of a bone and its
articular cavity, when the extremity is swung in such
a manner that the sides and extremities of the limb
circumscribe a conical space around an imaginary
THE CLASSIFICATION OF JOINTS
115
axis, the' base of the cone corresponding to the lower
extremity of the limb and the apex to the articular
cavity. This kind of movement is best seen in the
shoulder- and hip-joints.
FIG. 58
Right knee-joint. Anterior view. (Gray.)
Rotation. This is the movement of a bone upon an
axis, which is the axis of the pivot on which the bone
turns. This form is seen best in the rotation between
116 ARTICULATIONS OR JOINTS
the atlas and axis when the odontoid process of the
axis serves as a pivot around which the atlas turns.
The Apposition of Joint Surfaces. This is accom-
plished by (1) atmospheric pressure as in the hip-
joint; (2) synovial fluid; (3) ligaments to a small
extent; (4) muscles to the greatest extent. A short
muscle may act on more than one joint the gluteus
maximus extends the hip and also the knee through
its insertion into the fascia lata.
NOTE. The various articulations of the body have
not been described, as they are beyond the scope of
this book. However, a general understanding of their
attachment, position, and the bones they hold together
can be obtained from the plates.
QUESTIONS
1. Name the structures which enter into the formation of a
joint.
2. What are the functions of ligaments?
3. Describe a synovial membrane.
4. Give the varieties of synovial membranes.
5. Do joints contain a fluid? What is its function? Name?
6. Where are the varieties of synovial membranes located
usually?
7. Give the classification of joints included under the three
main groups.
8. Give examples of an immovable joint or synarthrosis. Mixed
joint or amphiarthrosis. Movable joint or diarthrosis. (See Table
of Articulations.)
9. What movements are admitted in joints generally?
10. What do you understand by flexion? Extension? Abduction?
Adduction? When occurring in the movements of a joint?
11. By what means are joint surfaces held in apposition?
12. What do you understand by the terms: Gliding movement?
Angular movement? Circumduction? Rotation?
CHAPTER VII
MUSCLE TISSUE
Myology is the branch of anatomy which describes
the muscles muscle tissue.
Muscle tissue consists of cellular elements arranged
in large masses to form muscles, which are attached
to the bones of the body, and enter into the structure
of numerous organs in such a manner that by their
contraction they are able to perform the various
movements of the body and functions of contained
organs, whether of a voluntary or involuntary
nature.
Classification. The varieties of muscles are:
voluntary striated, involuntary non-striated, and invol-
untary striated.
Voluntary Striated. These muscles are characterized
by being under the control of the will, also called
skeletal muscles, owing to their attachment to bones
which they move and assist to hold in position. Each
muscle if examined microscopically will be seen to
consist of a number of fibers, bound together by white
fibrous tissue. Each fiber is a long, narrow cylinder.
It varies in length from 1 to 5 inches, and exhibits
cross and longitudinal striations. The composition
of each fiber is a number of small fibers called
fibrillse, surrounded by a membrane the sarcolemma,
and separated by a clear, transparent substance
called sarcoplasm, and many peripherally located
nuclei. The sarcoplasm represents the true muscular
substance. The longitudinal striations or bands seen
are formed by the alteration of the fibrillse and the
sarcoplasm, but are not quite as distinct as the crossed
118
MUSCLE TISSUE
band. The crossed striations are due to the change in
the light and dark disks or bands.
The sarcolemma does not possess the inherent
quality of contractility, but the sarcoplasm does.
FIG. 59
FIG. 60
Part of a fiber of cross-striped muscular
tissue, showing the alternating bands.
(Gerrish.)
Diagram showing the minute
structure of cross-striped
muscular tissue. (Gerrish.)
It has been shown that the fibrillye form the fibers,
the latter being grouped into primary bundles called
fasciculi, and these primary bundles are collected into
a series of bundles called secondary bundles, and groups
of the latter form the completed muscle. Each muscle
is surrounded by a sheath of white fibrous tissue called
the epimysium, which gives off septa or layers from
CLASSIFICATION
119
its under surface to enclose the secondary bundles of
fibers. The primary bundles receive from the sheath
surrounding the secondary bundles a sheath called
the perimysium. The latter sends fibers that pass
between the individual fibers of the primary bundle,
called the endomysium.
FIG. 61
FIG. 62
Fragment of a fiber
of cross-striped mus-
cular tissue, showing
fibrils separated at
one end by teasing.
(Gerrish.)
Sheaths of muscular tissue in cross-section-
The muscular tissue does not appear, but is rep.
resented by the spaces between the partitions.
Outside of the entire muscle is epimysium;
between the bundles is perimysium; between the
fibers is endomysium the last shown in two areas
at the right. Diagrammatic. (F. H. G.)
The bloodvessels to muscle tissue pierce the epi-
mysium and give off branches which follow the larger
septa between the bundles until the perimysium is
reached and smaller vessels form, which pierce the
perimysium to form longitudinal capillaries; the latter
anastomose freely with each other.
The lymphatics are not numerous and are sometimes
wanting. The nerves follow the bloodvessels (see
nerve system nerve endings (page 339).
Voluntary striated muscles are found attached to
120 MUSCLE TISSUE
the skeleton and the external muscles of the eye-ball,
in the tongue, the pharynx, upper part of the esophagus,
anus, diaphragm, larynx, and external ear.
Involuntary Non-striated, Smooth or Visceral Muscle.
It is not under the control of the will. The individual
fibers are short, narrow, and spindle-shaped. Each
fiber is surrounded by a sheath, but it is not a sarco-
lemma. The fibers show longitudinal striation at the
periphery due to the presence of fibrillse, but no
transverse striation. There is only one nucleus, which
is narrow, elongated, and centrally located.
The fibers form bundles, but instead of being formed
into masses like the voluntary striated variety, they
are arranged into layers which extend circularly,
obliquely, and longitudinally in the construction of the
hollow organs of the body.
Bloodvessels are arranged as in the former variety.
The nerves are mostly derived from the sympathetic
system.
Non-striated muscles are found in the walls of the
alimentary tract, extending from the middle third
of the esophagus to the anus, in the ducts of glands,
trachea, and bronchial tubes, the eye"-ball, the internal
genito-urinary apparatus, walls of bloodvessels (except
the heart) and lymphatic system, and the capsules of
some organs.
Involuntary Striated or Cardiac Muscle. It is found
in the muscle of the heart. The fibers are short
cylinders, showing striations, but no sarcolemma. A
delicate sheath surrounds the fibers. The nucleus is
large, oval, and placed in the centre of a zone of un-
differentiated protoplasm, filled with pigment granules.
There are seen longitudinal and transverse striations
in this variety, the latter being fainter. The fibers of
this variety branch and join with the branches of other
muscle cells.
The bloodvessels are derived from the coronary
THE PROPERTIES OF MUSCLE TISSUE 121
arteries and small branches, are in intimate relation
with the fibers, the smaller branches running parallel
to the muscle bundles and sometimes lying within
them. The nerves are derived from the sympathetic
and cerebrospinal systems; sympathetic ganglion are
also present.
The Physiological Properties of Muscle Tissue.
Consistency. The consistency of muscle during life
depends upon the activity of the part upon which the
muscle is acting. Relaxed muscles are soft and fluc-
tuating; when touched under tension or doing work
the muscles are hard and resistant. The degree of
tension of course depends upon the size of the muscle
and the amount of work required.
Cohesion. Cohesion of muscle depends upon the
amount of connective tissue it contains; and it is this
which enables it to resist the forces of traction and
pressure.
Elasticity. Muscle possesses great elasticity, or the
power to stretch beyond its normal length through
the action of external forces, and of resuming the
normal length when those forces are removed. The
degree of elasticity of muscle during life depends
upon the proper amount of nourishment, exercise,
healthy condition of blood, unimpaired nerve supply,
and absence of any pathologic or diseased condition.
Should any of these conditions interfere, the elasticity
would be impaired.
Tonicity. This is the tension or tonus of the muscle
and is a property which is essential to counteract
the stretching of a muscle and then to return and
maintain it in a normal state, ready to be acted upon
by the ensuing contractions.
Irritability and Contractility. All muscles when
irritated by a stimulus will respond by a change of
shape, becoming shorter and thicker called muscular
contraction, and on withdrawing the stimulus the muscle
will resume its normal shape and position.
122 ^ MUSCLE TISSUE
The Muscle Stimuli. In the living body all muscle
tissue contracts in response to nerve impulses sent
from the central nerve system to the muscles. Experi-
mentally and artificially muscles are stimulated to
contract by various stimuli, e. g., mechanic pinching,
striking, or cutting a muscle; chemic, numerous chemi-
cal solutions; thermic, heated object, as hot needle or
wire will cause a rapid contraction; electric, as batteries
are used by physicians as therapeutic agents or upon
animal tissue during experiments in the laboratory.
Attachments of Muscles. Muscles are attached to
bones, cartilages, ligaments, or skin by means of short,
or long, rounded fibrous cords called tendons, or by
short, flat, fibrous membranes called aponeuroses. All
muscles, though they appear to be attached to bone or
cartilage, in reality fuse with the periosteum or peri-
chondrium at the point of attachment and do not
touch the bone or cartilage. Muscles attached to the
skin are flat and thin and their fibers fuse with the
areolar tissue just beneath the skin, as the muscles of
the face.
Muscles vary as to their form. Some are long, and
flat or round; others short, and flat or round; still others
triangular and quadrilateral in shape.
The origin of a muscle is called its head, and the
portion which intervenes between the head and
the tendon or aponeurosis is termed the belly or body
(venter) .
Muscles derive their names from the part of the body
in which they are situated; the tibialis anticus the
anterior tibial region, ulnaris ulnar region, radiali?,
radial region, etc. ; from the direction their fibers take
rectus abdominis, obliquus hallucis, transversalis;
according to their use or action flexors, extensors,
abductors, adductors, levators, compressors; from
their shape deltoid, trapezius, digastric; according
to their number of divisions biceps, triceps; from
ATTACHMENTS OF MUSCLES 123
their points of attachment sternohyoid, sternomas-
toid.
In describing a muscle we speak of its origin and
insertion, the former term meaning its more fixed
point or central attachment of the head, while the
latter means the movable point to which the force of
the muscle is directed and upon which it acts when
it contracts. However, the majority of muscles act
from either their point of origin or insertion. The
exceptions are the muscles of the face, which arise
from the bone and are inserted into the skin.
It must be remembered that no single muscle can
perform a movement alone: It requires several mus-
cles, one set to fix the limb or part called fixation
muscles, and another to act upon the part to be
flexed, extended, abducted, etc.
Tendons. Tendons when seen during life or in the
recent state are white, glistening, fibrous cords, of
different size and shape, some are long and short,
thick, rounded, and flattened; consist mostly of white,
fibrous tissue, very strong and non-elastic. Their
blood-supply is very scant. The smaller tendons not
showing a trace of blood. The nerve endings have
special terminations called neurotendinous spindles
or crgans of Golgi. The tendons are attached to the
belly of the muscle by one extremity; to the periosteum
of bone or perichondrium of cartilage by the other,
and are usually the part which is called the insertion.
However, some muscles have a tendon at either
extremity, as the biceps and triceps, and others present
two muscular bellies with a tendon between, as the
digastric muscle.
Aponeuroses. These are similar in structure to