102 



ANATOMY AND PHYSIOLOGY 



Subscapularis (Fig. 86). Origin. The subscapular fossa. 

 Insertion. The lesser tubercle of the humerus. 



Action. It holds the head of the humerus in place and rotates 

 it inward (the palm turns backward) . 



The deltoid (Fig. 85). Is triangular in shape and forms a 

 sort of cap over the shoulder- joint. Origin. The_ spine and' 



acromion of the scapula, and 

 the lateral portion ol the 

 clavicula. Insertion. The 

 jateral surface of the humerus 

 at the middle of the shaft, 



"on the deltoid tuberosity. 



Action.- Principally to 

 elevate the humerus to a 

 Horizontal position (acting 

 with the supraspinatus, an 

 abductor of the arm). 



Nerve. A xillary. 



The 



anterior 



(Figs. 75, 85). A large flat 



and important muscle wicn 

 lies between the scula'lin5 



19. 



FIG. 84. MUSCLES OF THE SHOULDER 



16% the thorax^ Origin.- By 



17 separate slips from eight ribs, _ 



on the front and side of the 

 Thorax, insertion. The ver- 

 tebral Sdrder of the scamrfa^ 

 It lies close to the side of 

 the thorax, covering a con- 



2, 3, 4, 5, Triceps; 6, attachment to siderable portion of the ribs t 



olecranon; 7, anconeus;~8, 8, g,jieltoid (por- 

 tion removed); 10, supraspinatus; n, infra- 

 spinatus; 12, 13, two extremities of teres 

 minor (intervening portion removed); 14, 



and intercostal muscles. 

 Three actions. It holds 



teres major; 15, latissimus dorsi; 16, 17, 18, the scapula firmly in plafo 

 19, muslces of forearm.-T^^.) and pulls it forward^ thus 



pushing the arm ahead. If the shoulders are held firmly jt can_ 



elevate the ribs, assisting inspiration. It sustains the weight of 



the body when resting upon hands and knees, as in creeps 



Nerve. Long thoracic or external respiratory. 



