222 HISTORY OF THE HUMAN BODY 



axial musculature, while other fibers, the anterior portion, no 

 longer show their segmental origin. Anterior to the girdle 

 lies the trapezius, now, like the anterior part of the latissimus, 

 showing no trace of myotomic origin, but undoubtedly from 

 that source originally. Ventral to these are seen two slips 

 clearly derived from the long superficial rectus, and still farther 

 ventral, covering the chest region, lies the voluminous pector- 

 aliSj still in part composed of slips attached to the myocom- 

 mata. Beneath these superficial layers are deeper muscles, like 

 the levator scapula and the serratus magnus, here plainly de- 

 rived from the axial muscles in the form of separating slips. 



Turning to the intrinsic muscles, it is seen that the outer 

 surface of the three portions of the girdle is covered with fan- 

 shaped sheets that converge to the head of the humerus, where 

 they insert near together. Of these the dorsalis scapulce cov- 

 ers the scapula, the procoraco-humeralis the procoracoid, and 

 the supracoracoideus the coracoid. 



^ Distal to these come the muscles, the bellies of which occupy 

 the region of the upper arm, and which may thus form a third 

 group. Of these there are three that occupy the flexor aspect, 

 and a complex one with several heads that lies upon the ex- 

 tensor aspect. Of the first the two coraco-brachiales, longus 

 and brevis, arise from the coracoid and insert on the humerus. 

 These lie on the medial side. On the outer or lateral side lies 

 the humero-antebrachialis, which arises along the humerus and 

 inserts by a tendon into the proximal end of the radius. The 

 complex muscle on the extensor side, the anconeus, is con- 

 stant in the character of arising from several heads and in 

 the insertion of all by a common tendon into the olecranon 

 process of the ulna, although the name of " triceps," applied to 

 this muscle in man, is objectionable, since the number of heads 

 is variable and three is by no means the typical number. Thus 

 here in Necturus there are four, a central superficial one from 

 the scapula, a median and a lateral one from the humerus and 

 a median one from the coracoid. The term anconeus, bearing 

 no suggestion of the number of points of origin, but referring 

 to its location alone (a^xou, elbow, ulna), is much preferable. 



