380 



THE MUSCULATURE 



extended tendon, from the supraglenoid tuberosity of the scapula. The fusiform 

 belly which arises from the fusion of these two heads is inserted into the radius and 

 into the fascia of the forearm. The brachialis (fig. 365) extends under cover of 

 the biceps from the lower three-fifths of the shaft of the humerus to the coronoid 

 process of the ulna. The muscles of this group are supplied by the musculo- 

 cutaneous nerve. The brachialis also usually receives a branch from the radial 

 nerve. The coraco-brachialis and short head of the biceps flex and adduct the 

 arm at the shoulder; the biceps and brachialis flex the forearm at the elbow. The 

 long head of the biceps abducts the arm at the shoulder. 



Fig. 364. — Superficial Muscles of the Front of the Arm. 



Pectoralis minor 



Coraco-brachialis 



Long head of triceps \ 



Medial head of triceps 



Tendons of insertion of pectoralis 

 major and deltoid 



Lateral head of triceps 



Brachialis 



Brachialis — 



Semilunar fascia 

 (lacertus fibrosus) 



Extensor carpi radialis longus 



Brachio-radialis 



The muscles of this Rroup un; found in most of the hmbed vertebrates. In many of the 

 lower forms the oonico-lirac-hiidis, whicli ;i|)pcurs farther down in the vertebrate series than the 

 biceps, has a inorc extensive instirtion than in man. It may extend to the uhia (Hzards) and 

 niay be subdivided into various muscles which correspond with the adductors of the thigh. The 

 biceps, tlie place of which is taken in the lower vertebrates by a coraco-radial muscle, in most 

 of the mammals presents two heads, the more lateral of which is attached by a tendon to the 

 scapula above the shoulder-joint. This long tendon jof the biceps lies primitively outside the 

 capsule of the shoulder-joint, but in some of the higher mammals has come to lie within the 

 capsule. In the biceps four elem(!nts may be recognised: — a coraco-radial, coraco-ulnar, gleno- 

 raflial, and gleno-ulnar. (Krause.) 'I'Ik; development, of these elements varies in different 

 mammals 



