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.
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.