MYOLOGY lOS 



internal head being located toward the deltoid attachment and the 

 external head into the pneumatic fossa. The long head extends 

 from a circumscribed area just posterior to the glenoid cavity of the 

 scapula. The fibers pass around the shoulder-joint, beneath the 

 deltoid. 



Insertion. — The broad tendon passes over the elbow-joint and is 

 inserted to the entire under surface of the olecranon of the ulna. 



Shape — ^Long, large, fleshy. 



Relations. — ^The supraspinatus passes between the internal and the 

 external heads. It is bounded by the biceps and the deltoid. 



Action. — ^An extensor of the antibrachial region directly antago- 

 nizing the biceps. 



Brachialis Anticus (Fig. 15, No. 9; Fig. 14, No. 5). Location. — 

 In the flexure of the humerus and the ulna. 



Origin. — ^It arises fleshy from a circumscribed area on the inner 

 side of the anconal part of the distal extremity of the humerus. 



Insertion. — The fibers passing directly over the elbow-joint become 

 inserted to the lateral surface of the proximal end of the ulna close 

 to the margin of the sigmoid cavity. 



Shape. — Small, fleshy. 



Relations — With the joint. 



Action. — ^Assists in flexing the forearm upon the arm. Protects 

 the structures in the anterior part of the elbow-johit. 



THE MUSCLES OF THE FOREARM AND THE HAND 



Extensor metacarpi radialis longior Extensor digitorum communis 



Supinator brevis Flexor metacarpi radialis 



Pronator brevis Pronator longus 



Extensor ossis metacarpi poUicis Anconeus 



Extensor indicis longus • Flexor digitorum subhmis 



Flexor digitorum profundus Flexor.carpi ulnaris 

 Flexor carpi ulnaris brevior 



Extensor Metacarpi Radialis Longior (Fig. 1 3 , No. 1 7) . Location. — 

 Superior to the radius. 



Origin — By two strong tendinous heads; the outer from the tuber- 

 cle of the external condyle of the humerus, just above the origin of 

 the tendon of the tensor patagii brevis; the inner and stronger 



