MUSCLES OF THE ANTERIOli EXÏEEM1TY. 91 



OS capliato-liamatum, it widens and is inserted into the outer border 

 of the metacarpal of the small finger. It draws this finger towards 

 the thumb. 



88. M. abductor dig. V primus (Figs. 77 and 78 ah^). 



Dugès, sous-pyro-pré-métacarpien du digitale, n. 93. 



This muscle arises from the palmar border and the outer surface 

 of the OS -pyramidale, and is inserted into the basal phalanx by a 

 thin tendon. 



89. M. abductor dig. V secundus (Figs. 77 and 78 ab^'\ 



Dugès, sous-pyro-post-métacarpien du digitale, n. 94. 



It arises from the posterior part of the os pp-amidale, is short, 

 and is inserted into the outer side of the metacarpal. 



(II.) Muscles on the dorsal surface. 



M. extensor digitorum communis longus (Figs. 75 ed and 77 ec). 



90. M. extensor digitorum commmiis Irevis (Fig. 79 e-^, e^, e^). 

 Dugès, sous-pyro-phalangettien du III, IV, V, n. 124, 128, 131. 



Covered by the foregoing, this muscle arises from the os pyra- 

 midale in conjunction with the extensor jpollicis and from the os 

 capitato-hamatum. The part destined for the third finger, together 

 with that for the fourth, arises from the os pyram.idale, passes 

 obliquely backwards into a tendon which runs along the inner side 

 of the corresponding finger to be inserted into the last phalanx. 

 That for the fifth finger arises from the inner projection of os 

 caintato-hamatum beuig* here attached to the insertion of the m. ex- 

 tensor carpi idnaris, and is inserted in a similar manner into the 

 terminal phalanx of the fifth finger. 



91. M. abductor digiti II (i. e. polUcis) longus (Figs. 74 ei and 

 79 ab.%). 



For the origin and course of this muscle in the forearm see 

 No. 63. The muscle passes obliquely over the wrist- joint from 

 the little finger towards the inner side and from before backwards, 

 it is inserted into the metacarpal of the second finger (thumb). 

 The place of insertion of this muscle into the metacarpal (compare 

 p. 47) is, in the males, developed into a ridge and process, the 

 muscle itself is enlarged during the breeding season. This muscle 

 abducts the thumb and by this means presses upon the chest of the 

 female when clinging to her. 



