104 ANATOMY OF THE DOMESTIC FOWL 



THE MUSCLES OF THE BRACHIAL REGION 



Biceps Triceps 



Deltoid Brachialis anticus 



Biceps (Fig. 13, No. 8). (Synonym. Biceps brachii.) 



Location. The anterior brachial region. 



Origin. By a broad tendon it covers the top of the shoulder- 

 joint, dividing into two heads, giving rise to the long and the short 

 heads. The long is inserted into the outer part of the head of the 

 coracoid just beyond the glenoid cavity; the short head to the 

 distal angle of the ulnar tuberosity of the humerus. 



Insertion. To the ulna just in front of the articular cavity for 

 the trochlear surface of the distal extremity of the humerus. 



Shape. Large, subfusiform. 



Relations.' On one side by the triceps and the other the deltoid 

 and anteriorly partially covered by the patagii muscles. 



Action. A powerful flexor of the forearm. 



Deltoid (Fig. 13, No. 12; Fig. 15, No. 8). Location. Occupying 

 the lateral side of the humerus; the brachial region. 



Origin. Divided into two portions, the long narrow head extends 

 from the clavicular process of the scapula and from the adjacent 

 surface of the same bone. These fibers then extend around the back 

 of the shoulder-joint, and are joined by the fibers that arise from 

 the entire outer surface of the large os humero-scapulare. These 

 latter fibers are inserted upon an extensive area upon the anconal 

 part of the bone beyond the humeral articular head, and to almost 

 the entire shaft below it. 



Insertion. By a subcylindrical tendon to the proximal side of the 

 tubercle of the external condyle, and above the insertion of the 

 extensor metacarpi radialis longus. 



Shape. Large, fleshy, with tendinous attachment. 



Relations. On one side by the biceps and the other by the triceps 

 also the patagii. 



Action. To extend the arm. 



Triceps (Fig. 15, No. 7). (Synonym. Triceps brachii.) 



Location. The posterior humeral region. 



Origin. By three portions: by the internal and external heads, 

 and by the long scapular head. The internal and the external 

 heads are blended except at their proximal extremities. Each head 

 arises from the anconal surface of the shaft of the humerus. The 



