MYOLOGY 85 



M. extensor digitorum longus (figs. 6, 17, 18, 32) 

 in reality constitutes an extensor digitorum communis, 

 but the more usual name will be employed. It has origin 

 by a long, flat tendon from the lateral epicondyle of the 

 femur. It passes deep beneath the origin of the tibiahs 

 anticus and the rather slender muscular portion Hes deep 

 and caudad to the latter. Well proximad upon its belly 

 an aponeurosis develops, which narrows to a tendon pass- 

 ing beneath the transverse Ugament and over the instep. 

 At about the transverse Hgament it spUts into four parts 

 which shortly separate, each passing to the medio-cranial 

 margin of one of the four lateral digits. 



The three extensor muscles of the calf are served by the 

 N. peroneus profundus. 



The peroneal group of muscles, numbering four, is also 

 very well developed in this genus. The interconnection 

 between their fibers is very close, but one will have no 

 trouble in dissecting them if he follows up their tendons. 

 They consist of 



Mm. peroneus longus peroneus digiti quarti 



peroneua brevis peroneus digiti quinti 



M. peroneus longus (figs. 6, 17, 32, 33) has origin 

 from the latero-cranial or peroneal process upon the head 

 of the fibula. It passes superficially between the tibiaUs 

 anticus and the peronei quarti and quinti. The super- 

 ficial peroneal nerve passes deep between this and the last 

 two muscles. Its tendon extends over the external mal- 

 leolus and the peroneal groove on the medio-ventral part 

 of the cuboid, and is inserted upon the ventral aspect of the 

 ectocuneiform only (apparently not onto the first meta- 

 tarsus, as Parsons (1894, p. 290) claims is the case in most 

 rodents). 



M. peroneus brevis (figs. 18, 32, 33) has origin along 

 the entire medio-caudal shaft of the fibula and the portion 



