146 couES, 



partly iiuder, the whole coracoid apparatus, and upon the posterior 

 aspect of the proximal moiety of the humerus. Viewed at first from 

 the outside, superficially, it appears to arise from coracoid proper, 

 and to descend thence upon the humerus. But its real origin is much 

 more extensive, from the whole, or nearly all, of the under (internal) 

 surface of the epicoracoid lamella, as a thin expanded plane, whose 

 contour is determined by that of the bony plate just named. It 

 gains the outside by curving around the coracoid proper, reminding 

 one of the escape of the iliacus over the pelvic brim, or of oblurator 

 internus over the border of the ischium. It has a broad fleshy in- 

 sertion into the expanded surface of the humerus, upon the aspect of 

 that bone above noted, as far down as the insertion of the latissimus. 

 These coraco-humeral muscles adduct and retroduct the arm, bring- 

 ing it upon the breast, as in the act of clasping ; and have further- 

 more somewhat the action of internal rotators of the bone. 



This extensive and somewhat complicated disposition of the coraco- 

 brachial muscles, and their perfect diflerentiation into two, are in 

 striking contrast with the singularly small and simple condition of 

 the (single) muscle in some animals of the next order above, as the 

 opossum for instance. It is the nearest approach of which we are 

 aware, to the ordinary condition of the antitypic muscles of the 

 hind limb, which are always differentiated into several adductores 

 femoris. 



h. Acting upon forearm. 



Only one forearm muscle comes from the body : it is the slip from 

 the latissimus. Of the other " long " brachial muscles, the biceps is 

 doubled above, and has a singular disposition; the scapular head of 

 the ti'iceps ("long" extensor cubiti) is entirely discrete from both the 

 other ("short " extensors) heads, for a reason we disclose below. The 

 brachialis anticus ("short" flexor cubiti) is not remarkable. Per- 

 haps the most interesting point regarding the muscles of this part is 

 the remarkable development of the anconseus, and the presence of 

 another antagonistic anconeeus, both in subserviency to the peculiar 

 motion that the elbow-joint permits in lieu of pronation. The pro- 

 nator teres — that very constant muscle in higher vertebrates — is 

 present under ordinary conditions, although there is no pronation pos- 

 sible in the forearm ; so also are the two supinators (but the prona- 

 tor quadratus is wanting?). 



Before proceeding to consider the muscles that act upon the fore- 

 arm, we may notice the method of adapting the whole limb for use 

 as a paddle. The humerus, as we have already seen, is extremely 

 short and thick, and is especially broad across the condyles, where 

 the width is but little less than its whole length. We have also seen 

 that the principal muscles that extend, i. e., retroduct, the humerus. 



