

MUSCULAR SYSTEM OF MAMMALIA. 33 



differ in their proportions from those in the human subject, 

 dependent upon the shape of the scapula. 



The ' deltoid ' extends forward in nearly the same direction as 

 the infraspinatus, and has been named by hippotomists the 

 t abductor longus brachhV The e coraco-brachialis ' takes its 

 origin from the tubercular remnant of the coracoid situated 

 upon the superior costa of the scapula: the biceps has but 

 one origin, with which the coraco-brachialis is in no way con- 

 nected. The ' brachialis internus,' fig. 12, w, has the same 

 arrangement as in the human subject : it is the ' short flexor of 

 the fore-arm.' The 'triceps extensor cubiti,' fig. 11, c, consists 

 of three portions similar to those named in the human anatomy 

 the long extensor, the short extensor, and the brachialis ex- 

 ternus: there is also a fourth portion, derived from the common 

 tendon of the latissimus dorsi and teres major, by the inter- 

 vention of which it takes its origin from the inferior margin of 

 the scapula. 



As might be expected from the construction of the bones of the 

 forearm, both the pronator and supinator muscles are wanting. 

 The ' extensor carpi radialis,' fig. 11, a, b, is here single, arising 

 from the anterior part of the external condyle of the humerus, 

 and from the external surface of that bone for a considerable 

 distance : it forms a strong fleshy belly, terminating in a powerful 

 tendon, which runs to be inserted into the base of the anterior 

 surface of the metacarpal. This muscle seems, from the extent 

 of its origin, to represent the long supinator and the two radial 

 extensors of the wrist combined, and all three thus co-operate in 

 the extension of the wrist. There is but one 'flexor carpi radialis,' 

 fig. 12, p ; it arises from the external condyle of the humerus, 

 and is inserted into the posterior surface of the base of the 

 metacarpal, forming the antagonist to the preceding muscle. 

 The ( flexor carpi ulnaris ' arises from the posterior part of the 

 external protuberance of the os humeri, and also by a distinct 

 head from the protuberance situated above the internal condyle ; 

 its tendon is inserted into the pisiform bone and into the base of 

 the rudimentary metacarpal beneath it. The ' extensor carpi 

 ulnaris' arises from the posterior part of the external condyle 

 of the humerus, and is inserted, like the preceding, into the os 

 pisiforme, whence it is prolonged beneath the carpus, so as to 

 perform the office of a flexor of the wrist. The ' extensor com- 

 munis digitorum,' fig. 11, k, arises from the external condyle 

 of the humerus and from the contiguous fascia, also from 



VOL. III. D 



