176 ANTHROPOID APES. 



appear to take a lateral direction. The Tendo 

 Achillis is preseut, but it has not the prominent 

 development in height and width which we observe 

 in man. The long extensor, flexor, and tibial 

 muscles are in all cases fully developed. The 

 peroneus tertius, as it is termed, although it should 

 only be regarded as a part of the extensor longus 

 digitorum, is absent in anthropoids.* I myself am 

 not disposed, with Huxley, Bischoif, and others, to 

 regard this muscle as an abductor. Briihl perceived 

 in a chimpauzee a fuuith rudimentary peroneal 

 muscle [Musculus iwrorieus intermedius), extending 

 between the peroneus and the little toe, a muscle 

 sometimes found in man, and which I have myself 

 only observed in one adult chimpanzee. In the 

 gorilla and the chimpanzee the extensor longus 

 digitorum passes through a remarkably strong trans- 

 verse ligament, formed of fibrous cartilage, which 

 covers the tarsus. It acts upon the four outer toes 

 (Fig. 55). Bi'iihl has described the characteristic 

 contraction and extension of the tendons of the long 

 and short extensors of the toes in the chimpanzee, 

 but I have myself found some difficulty in producing 

 this action. In Fig. 55 I have endeavoured to repre- 

 sent this condition in the most natural way. The ex- 

 tensor proprius poUicis is in all cases developed. The 

 extensor brevis digitorum produces a large, oblique 

 belly for the great toe (Fig. 55). In the gorilla there 

 is for the great toe an abductor, a bicipital flexor, an 

 adductor, and an oj)ponens (comp. Fig. 54). 



* Euge also considers this muscle to be part of tho extensor 

 longus digitorum. 



