TERES MAJOR. SUBSCAPULARIS. 



217 



margin of a triangular space, of which the other sides are the upper part of the humerus, and 

 the axillary border of the scapula, covered before by the subscapular and behind by the teres 

 minor muscles ; this triangle is divided by the long head of the triceps into an external, 

 quadrilateral, and an internal, triangular compartment. Through the quadrilateral space pass 

 backwards the posterior circumflex vessels and the circumflex nerve ; and in the triangular 

 subdivision the dorsal branch of the subscapular artery passes round the margin of the scapula 

 into the infraspinous fossa. 



Varieties. The teres major muscle is sometimes found connected with the fasciculus of 

 the latissimus dorsi arising from the same part of the scapula. A slip from this muscle has 

 been observed joining the long head of the triceps, and also one descending upon the fascia 

 of the upper arm externally. 



Fig. 233. MUSCLES OF THE RIGHT SHOULDER AND 

 ARM, SEEN FROM BEHIND. (Allen Thomson. ) i 



The acromion process and a part of the spine of 

 the scapula, with the deltoid muscle, have been re- 

 moved, a, coracoid process ; 6, triangular surface 

 at the root of the spine ; c, is close to the cut por- 

 tion of the spine ; d, great tuberosity ; e, ole- 

 cranon ; /, is close to the external condyle and head 

 of the radius; 1, supraspinatns ; 2, infraspinatus ; 

 3, teres minor ; below the figure is the triangular 

 space ; 4, teres major ; 5, part of latissimus dorsi ; 

 + , slip from the inferior angle of the scapula ; f, on 

 the edge of the humerus. points to the tendon of the 

 latissimus dorsi and the quadrangular space ; 6, 

 scapular head of the triceps, passing above between 

 the teres major and minor ; 6', external head ; 6", 

 part of the muscle arising below r the spiral groove, 

 belonging to the internal head ; b'", inner part of the 

 internal head ; 7, anconeus. 



The subscapularis muscle (tig. 234, 5) 

 arises partly by muscular and partly by 

 tendinous fibres from the venter of the 

 scapula, with the exception of the neck 

 and the spaces occupied by the serratus 

 magnus, but including the groove along 

 the axillary border of the bone. The 

 greater number of its fibres unite into a 

 broad tendon which is inserted into the 

 impression on the small tuberosity of the 

 humerus ; some of the lower fibres, how- 

 ever, are directly inserted into the bone 

 for a short distance farther down. Three 

 or four tendinous septa, attached to the 

 ridges of the subscapular fossa, pass out- 

 wards in the origin of the muscle, others 

 are prolonged inwards from the tendon 

 of insertion, and fleshy fasciculi pass obliquely between the two sets. 



Relations. The tendon of the subscapularis is incorporated with the capsule of the 

 shoulder- joint, and between its upper border and posterior surface, and the coracoid process 

 and neck of the scapula is a bursa usually communicating with that joint. There is some- 

 times another bursa intervening between the anterior surface of the muscle and the upper 

 ends of the biceps and coraco-brachialis muscles. Anteriorly the muscle is in contact 

 at its origin with the serratus magnus, and is covered at its insertion by the coraco- 

 brachialis and biceps, while in the interval between it forms part of the posterior wall of 

 the axilla. 



Varieties. The varieties hitherto observed in this muscle are not considerable. A small 

 additional muscle is sometimes found, passing from the upper part of the axillary border of 

 the scapula to be inserted, at the lower margin of the subscapularis, into the capsular liga- 



