482 THE ANATOMY OF VEETEBRATED ANIMALS. 



greatest in the Oi'ang, in wliicli the hallux is hahitually 

 directed at right angles to the long axis of the foot. The 

 distal jphalanx of the hallux is not unfrequently absent in 

 the Orang. 



All the Antliropomorpha possess certain muscles which 

 are not usually found ia Man, though they may occiir as 

 varieties in the human subject. These are the levator 

 claviculce, the dorso-epitrochlearis, the scansorius,* and' the 

 abductor ossis metacarpi quinti digiti. They are also devoid 

 of two muscles which are usually present in Man — the ex- 

 tensor primi internodii polKcisf and the peronceus tertius. 

 The former of these is sometimes, and the latter frequently, 

 wanting in the human subject. 



The flexor accessorius appears to be regidarly absent in 

 Hylohates and Pithecus, and, in the majority of cases, in the 

 Chimpanzee. The transversus pedis seems to be absent in 

 the Orang, but it is present in the other Antliropomorpha. 



Many muscles which exist both in these Apes and iu Man 

 have different origins in the former. Thus, the solceus 

 has only a fibular head, and takes no origin from the 

 tibia. The flexor brevis digitorum pedis never arises 

 altogether from the calcaneum, but a large proportion 

 of its fibres spring from the tendons of the deep flexors. 

 The calcaneal head furnishes the tendons for the second, 

 or the second and third, digits. The interosseous muscle 

 which lies on the tibial side of the middle digit of the 

 pes, usually ai'ises from the fibular side of the second 

 metatarsal as well as from the tibial side of its own meta- 

 tarsal, and its origin lies on the dorsal side of that of the 

 fibular interosseous muscle of the second digit. Hence, of 

 the so-ca.lled dorsal interossei (or interossei which are visible 

 on the dorsal aspect of the pes) two belong to the middle 

 digit, and one, to the second and fourth digits respectively ; 

 which is the same arrangement as that which obtains in the 



* Kot actually described in the Gorilla, and absent in some Chim- 

 panzees. 



t The former muscle is said to be present by several anatomists 

 in the Chimpanzee and other Apes ; but what they have taken for it 

 is the metacarpal division of the extensor ossis metacarpi. 



