OF THE DIFFERENT MUSCLES. 153 



Use. — To assist in the flexion of the humerus. 



TERES MAJOR AND TERES MINOR. 



Origin. — From the posterior angle and costa of the 

 scapula. 



Use. — These muscles assist in bending the shoulder joint, 

 and roll it outwards and inwards. 



SUBSCAPULARIS. 



A muscle of triangular figure, rilling up the hollow of the 

 scapula. 



Origin. — From the surface and circumference of the sub- 

 scapular fossa. 



Insertion. — Into the small tubercle of the os humeri. 



Use. — To assist in the extension of the shoulder joint, and 

 to turn the humerus inwards. 



POSTERIOR HUMERAL REGION. 



TRICEPS EXTENSOR BRACHII. 



This muscle consists of three distinct portions, called its 

 heads. The first takes its origin from the posterior costa of 

 the scapula ; from which its fibres run to the point of the 

 olecranon. The second takes its origin from the outward sides 

 of the neck and body of the os humeri, and unites with the 

 former. The third arise from the inward part of the os hu- 

 meri, and unites with the others prior to their insertion. 



Insertion. — By a strong but short tendon, into the olecra- 

 non of the ulna : some of its fleshy fibres are continued down 

 upon the fascia of the arm. 



Use. — To extend the arm. 



ANTERIOR HUMERAL REGION 



Comprehends those muscles which are seen in front of the 

 humerus. 



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