UPPER EXTREMITY AND THORAX, ANTERIOR. 285 



Biceps. Figs. 62, 63. 



Origin. By a long tendinous head from the top of the 

 glenoid cavity of the scapula, by a shorter muscular head 

 from the coracoid process of the same bone. 



The former ten don passes over the top of the head of the 

 humerus within the capsular ligament of the shoulder, and 

 blends with the glenoid ligament, and the latter has a com- 

 mon origin with the coracobrachialis muscle. 



Insertion. By the broad expansion into the deep fascia 

 of the forearm. By the tendon into the posterior margin 

 of the bicipital tuberosity of the radius. 



Nerve Supply. From the musculocutaneous, which 

 brings fibres from the sixth and seventh cervical nerves. 



Action. (i) It is a feeble flexor and adductor of the 

 arm. Serves to retain the head of the humerus in the 

 glenoid cavity. (2) On the forearm. A strong flexor 

 of the forearm. If the forearm has been pronated the 

 biceps acts as a strong supinator, the strength of its action 

 of supination increasing until it is the strongest when the 

 forearm is at right angles with the arm. 



Brachialis Anticus. Figs. 63, 67. 



Origin. From the anterior surface of the shaft of the 

 humerus below the insertion of the coracobrachialis and 

 deltoid (the latter it embraces), and from the anterior sur- 

 face of the internal intermuscular septum. 



Insertion. The rough surface at the front and inside of 

 the base of the coronoid process of the ulna. 



Nerve Supply. By the musculocutaneous in front and 

 the musculospiral behind. The sixth and seventh cervical 

 nerves supply the filaments. 



Action. To flex the forearm upon the arm, or the 

 reverse. 



