(Fig. 77.)
=M. subscapularis= (Fig. 77, _a_).--A triangular mass from the
subscapular fossa to the lesser tuberosity of the humerus.
_Origin_ (Fig. 78, _a_).--From the whole subscapular fossa except along
the fusiform area for the attachment of the levator scapulæ and the
serratus anterior near the vertebral border, and except over a
quadrangular area about one centimeter long near the glenoid angle. The
origin is by fleshy fibres directly from the periosteum except along two
or three lines marked by oblique ridges. To these lines are attached
tendinous fibres. At the glenoid border the area of origin sometimes
occupies part or the whole of the surface of the fossa for the origin of
the teres major, so that the teres arises from the fascia on the surface
of the subscapularis. At the coracoid border some of the fibres may take
origin from the adjacent fascia of the supraspinatus (Fig. 77, _d_).
_Insertion_ (Fig. 82, _b_).--The fibres converge to the glenoid border,
and the insertion is by a strong, flat tendon into the dorsal border of
the lesser tuberosity of the humerus.
[Illustration: FIG. 77.--MUSCLES ON THE MEDIAL SIDE OF THE ARM.
M. epitrochlearis, M. clavobrachialis, and the breast-muscles have
been removed. _a_, M. subscapularis; _b_, insertion of M. levator
scapulæ and of M. serratus anterior; _c_, M. teres major; _d_, M.
supraspinatus; _e_, M. latissimus dorsi (_e′_, cut edge of that part
which becomes united with the bicipital arch); _f_, M.
coracobrachialis; _g_, M. biceps brachii (the capsule of the joint has
been laid open to show its tendon); _h_, cut insertions of pectoralis
muscles; _i_, caput longum of M. triceps brachii; _j_, long portion of
caput mediale of M. triceps brachii; _k_, intermediate portion of
caput mediale of M. triceps brachii; _l_, short portion of caput
mediale of M. triceps brachii; _m_, cut end of M. clavobrachialis;
_n_, M. brachioradialis; _o_, M. extensor carpi radialis longus; _p_,
M. extensor carpi radialis brevis; _q_, M. pronator teres; _r_, M.
flexor carpi radialis; _s_, M. palmaris longus (_s′_, its tendons);
_t_, M. flexor carpi ulnaris (_t_, ulnar head; _t′_, humeral head);
_u_, third head of M. flexor profundus digitorum; _u′_, fifth head of
M. flexor profundus digitorum; _u″_, one of the tendons of M. flexor
profundus digitorum; _v_, M. pronator quadratus; _w_, M. abductor
brevis pollicis; _x_, ulnar part of M. flexor sublimis digitorum. 1,
transverse ligament of the wrist.]
_Relations._--Lateral surface with the scapula and the capsule of the
shoulder-joint. Medial surface with the levator scapulæ (Fig. 73, _h_),
serratus anterior (Fig. 73, _i_), part of the scalenus (Fig. 73, _f_),
the transversus costarum (Fig. 73, _j_), and the coracobrachialis (Fig.
77, _f_). Cranial border with the supraspinatus (Fig. 77, _d_). Caudal
border with the teres major (Fig. 77, _c_) and infraspinatus (Fig. 75,
_c_).
_Action._--Pulls the humerus inward (mediad).
=M. teres major= (Fig. 75, _d_; Fig. 77, _c_).--A thick muscle,
triangular in cross-section, lying parallel with the glenoid border of
the scapula.
_Origin_ (Fig. 76, _j_; Fig. 78, _b_) from the vertebral one-third of
the glenoid border of the scapula, and from fascia covering the
subscapularis (Fig. 77, _a_) and the infraspinatus (Fig. 75, _c_) over a
small area near the glenovertebral angle of the scapula. It may touch
the insertion of the rhomboideus.
_Insertion_ (Fig. 82, _f_) by a tendon common to it and the latissimus
dorsi (Fig. 79, _d′_), as already described.
_Relations._--Outer surface with the caput longum (Fig. 75, _g_) and the
long portion (Fig. 80, _f_) of the caput mediale of the triceps, the
latissimus dorsi (Fig. 77, _e_), and the cutaneus maximus. Inner surface
with the serratus anterior (Fig. 73, _i_), the scalenus (Fig. 73, _f_),
the transversus costarum (Fig. 73, _j_), and the biceps (Fig. 77, _g_).
Dorsal border with the subscapularis (Fig. 77, _a_) and infraspinatus
(Fig. 75, _c_).
_Action._--Rotates the humerus inward and flexes it in opposition to the
infraspinatus, teres minor, and the deltoidei.
[Illustration: FIG. 78.--MEDIAL SURFACE OF THE SCAPULA WITH THE AREAS
OF ATTACHMENT OF MUSCLES.
_a_, M. subscapularis; _b_, M. teres major; _c_, M. serratus anterior;
_d_, M. levator scapulæ; _e_, M. rhomboideus; _f_, M.
occipitoscapularis; _g_, M. biceps; _h_, M. coracobrachialis; _i_,
caput longum of M. triceps.]