204 MYOLOGY, OR ANATOMY OF MUSCULAR SYSTEM 



and inserted into the upper end and outer border of the tendon. 

 The internal or deep head (anconeus internus) rises from the 

 whole posterior surface of the humerus below the spiral groove, 

 from the lower part of the external intermuscular septum, 

 from the whole of the internal, as high as the teres major; 

 some of its fibers are inserted directly into the olecranon, 

 but most join the deep surface of the tendon. The common 

 tendon is inserted into the tuberosity of the olecranon, and 

 externally a band is prolonged over the anconeus to the fascia 

 of the forearm and posterior border of the ulna; it may send 

 a slip to the capsule. 



On removing the triceps a few muscular slips are sometimes 

 found from the bone to the capsule, analogous to the sub- 

 crureus, and described by some as distinct from the triceps, 

 called the subanconeus. 



There is a bursa between the tendon and olecranon or in 

 the tendon, sometimes one between the integument and tendon, 

 rarely one between the tendon and ulnar nerve (retroepitroch- 

 lear). 



Nerves. Coracobrachialis and biceps by the musculocuta- 

 neous (fifth and sixth cervical), the brachialis anticus by the 

 musculocutaneous, triceps by the musculospiral (seventh and 

 eighth cervical). 



Actions. Biceps flexes the arm at the shoulder and the 

 forearm at the elbow; after pronation of the forearm it is a 

 powerful supinator and makes tense the fascia of the forearm; 

 its inner head and coracobrachialis draw the arm in as well 

 as up. The brachialis anticus is a simple flexor at the elbow. 

 Triceps, internal and external heads are extensors at the elbow; 

 the long head extends the arm on the scapula, keeps the head 

 of the humerus in place, and assists in extending the forearm. 

 These muscles may act from distal fixed points, as in climbing. 



MUSCLES AND FASCLffi OF THE FOREARM 



The superficial fascia is most distinct at the elbow, contains 

 the superficial veins, and below connects the skin with the 

 palmar fascia. 



The aponeurosis of the forearm (deep fascia) is composed 

 largely of transverse fibers, strengthened by expansions from 



