242 Region of Shoji/der 



with the long head of the biceps, and the insertions of the pectoralis 

 major, latissimus dorsi, and teres major ; the anterior and posterior 

 circumflex vessels and circumflex nerve, and the outer and long heads 

 of the triceps. 



Abscess in the shoulder-joint in the sub-deltoid bursa may reach 

 the surface by openings around the edges of the muscle, but the pus 

 rarely finds its way through the substance of the muscle. 



The supra-spinatus arises in the supra-spinous fossa and is in- 

 serted into the upper part of the greater tuberosity. It passes over the 

 shoulder-joint, so, in sub-glenoid dislocation, it is tightly stretched, 

 and holds and firmly hitches the head of the humerus against the lower 

 rim of the socket. It is to relax this muscle that the arm is first 

 abducted in the scientific method of reduction. 



The infra-spinatus and teres minor arise from the infra-spinous 

 fossa, and are inserted into the outer side of the greater tuberosity, the 

 teres minor being the lower of the two. They are external rotators. 



The supra- and infra-spinatus are supplied by the supra-scapular 

 nerve ; and the teres minor is supplied by the ganglionic branch of 

 the circumflex. 



The subscapularis arises from the vertebral two-thirds of the venter 

 of the scapula, and by tendinous intersections from the ridges ; it is 

 inserted into the lesser tuberosity and into the bone just below it. Its 

 tendon blends with the capsular ligament, but is separated from the 

 neck of the shoulder-blade by a bursa. It forms part of the posterior 

 wall of the axilla, and has resting upon it the origin of the coraco- 

 brachialis and biceps, and the axillary vessels and nerves. It is 

 supplied by the upper and middle subscapular nerves, and its action 

 is to roll the humerus inwards. 



The teres major arises from the dorsal surface of the lower scapular 

 angle, and, passing on the inner side of the shaft of the humerus, is 

 inserted into the inner lip of the bicipital groove. 



The latissimus dorsi arises from the back of the iliac crest, the 

 lumbar, and the lower six dorsal spines, and the lowest ribs (inter-digi- 

 tating with the external oblique). Its tendon curls round, and is inserted 

 in front of, that of the teres major, reaching the depths of the groove. 

 (Sometimes a muscular slip of the latissimus crosses over the axillary 

 vessels to be inserted with the pectoralis major.) These muscles 

 draw the humerus downwards and backwards, and rotate it inwards ; 

 they are supplied by the middle and long subscapular nerves. 



Though the latissimus dorsi is the lowest muscle in the posterior 

 wall of the axilla', its tendon, which has curled round the teres major, 

 does not descend so far along the humerus. Thus the muscles forming 

 the back of the axilla are to be given in this order : subscapularis, teres 

 major, and latissimus dorsi ; but the artery lies on them in this order : 

 subscapularis, latissimus dorsi, and teres major. 



Occasionally a bursa exists between the upper border of the latis- 



