102 



ANATOMY AND PHYSIOLOGY 



10 



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 of the 

 clavicula. Insertion. The 

 lateral surface of the humerus 

 8 at the middle of the shaft, 

 2 on the deltoid tuberosity. 



Action. Principally to 

 .9 elevate -the humerus to a 

 horizontal position (acting 

 with the supraspinatus, an 

 abductor of the arm). 



13 



15 



Nerve. A xillary. 



The serratus anterior 



(Figs. 75, 85). A large flat 

 and important muscle which 

 lies between the scapula and 

 the thorax. Origin. By 

 ...... i? separate slips from eight ribs, 



on the front and side of the 

 thorax. Insertion.* The ver- 

 tebral border of the scapula. 

 It lies close to the side of 

 FIG. 84. MUSCLES OF THE SHOULDER. the thorax, covering a con- 

 i 2. 3, 4, St Triceps; 6, attachment to siderable portion of the ribs 



olecranon; 7, anconeus; 8, 8 9, deltoid (por- , intprrnstal miic:rlp<; 



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



spinatus; 12, 13, two extremities of teres Three actions. It holds 



minor (intervening portion removed); 14, 



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



I9 ' muslces and pulls it forward, thus 



pushing the arm ahead. If the shoulders are held firmly it can 

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

 the body when resting upon hands and knees, as in creeping. 

 Nerve. Long thoracic or external respiratory. 



