142 couES, 



VIII. Muscles of the anterior extremity. 



The arrangement indicated in the beginning seems to us fully as 

 convenient as, and much more natural than, grouping the muscles of 

 the limbs upon, and naming the several sets after, the parts upon 

 which they lie, instead of those on which they act. 



The humerus, like that of the mole, an animal which uses its fore- 

 limbs in corresponding manner, is short, thick and extremely irregular 

 in superficies, with strong elevations and depressions for advantageous 

 arrangement of the muscles. The bone may be regarded as a knotty 

 osseous nodule interposed between shoulder and elbow-joint for the 

 strong movement of the forearm in several directions ; itself moving 

 through little space, but capable of being very powerfully pulled in 

 every direction, and thus laying the foundation, as it were, for the 

 various strong movements of the forearm. It is acted upon, from 

 the body, by the dermo-brachial slip already described, and by the two 

 following muscles : — 



a. Acting upon the humerus. 



(a'. — From the body.) 



Latissimus dorsi. — Notable for its extensive costal, and correspond- 

 ingly slight spinal, origin. It arises by aponeurosis from about 6 

 dorsal vertebrae (4th-9th), beginning above at a point just opposite 

 the shoulder, to which, therefore, the upper border passes directly 

 transverse ; most of this spinal portion is thicker than the costal. 

 The latter origin is by a series of fleshy slips from the 7th to the 14th 

 ribs, in a slightly irregular curved line the convexity of which is for- 

 ward ; the digitations are separable for some distance, especially the 

 few lower ones. No aponeurosis connects this costal with the spinal 

 portion ; such fascia having apparently been appropriated by the lower 

 trapezius and costal slip of panniculus, already described. The 

 lower, outer border of the muscle ascends very obliquely ; before in- 

 sertion, there is a complete twist, as usual, the upper fibres becoming 

 lower by twisting outwards; and conversely. Insertion by a short, 

 wide, thin, flat tendon in an oblique line upon the humerus, half-way 

 up the pectoral crest, and thence along the entocoudylar ridge to the 

 elbow. The muscle has its ordinary action, very advantageously 

 efl'ected by its extensive and low insertion. 



Pectoralis major. —^ Of remarkable extent. Its origin is in a line from 

 the acromion and whole episternal bar, and thence down the manu- 

 brium and sternum and linea alba to within a couple of inches of the 

 pubes. Along the front of the chest it has thick fleshy origin from 

 the ends of the ribs as well as from the breast bone. The abdominal 

 portion is extremely thin — thinner than the same part of the pannic- 

 ulus ; the muscle thickens rather abruptly as it passes over the lower 



