212 STRUCTURE OF THE APE AND MAN. 



dyle of the femur. The fibula is entire, and articulated 

 with the tibia at both ends. The tarsus has the same 

 number and relative position of the bones as in man ; bat 

 the heel-bone is shorter, and the whole foot rather more 

 obliquely articulated upon the leg, the power of grasping 

 being more cared for than that of supporting the body ; 

 the innermost toe forms a large and powerful opposable 

 thumb. 



There is a well-marked gradation in the quadrumanous 

 series from the ordinary quadrupedal to the more bipedal 

 type. In the lemurs and South American monkeys, the 

 anterior thumb is shorter and much less opposable than 

 the hinder one ; in the spider-monkeys it is wanting, and 

 a compensation seems to be given by the remarkable pre- 

 hensile faculty of the curved and callous extremity of the 

 long tail. This member, in the African and Asiatic mon- 

 keys, is not prehensile, but the thumb of the fore-hand is 

 opposable. In the true apes, the tail is wanting, i. e. it is 

 reduced to the rudiment called "os coccygis;" but the 

 fore-arms are unusually developed in certain species, hence 

 called " long-armed apes." These can swing themselves 

 rapidly from bough to bough, traversing wide spaces in 

 the aerial leap. The orang (Fig. 45) is also remarkable 

 for the disproportionate length of the arms, but this dif- 

 ference from man becomes less in the chimpanzees. The 

 large species called Gorilla, which of all brutes makes the 

 nearest approach to man, is still strictly " quadrumanous;" 

 the great toe, or "hallux," being a grasping and oppos- 

 able digit. But the hiatus that divides this highest of the 

 ape tribe from the lowest of the human species, is more 

 strikingly and decisively manifested in the skull (Fig. 50). 

 The common teeth in the male gorilla are developed, as 

 in the male orang, to proportions emulating the tusks of 



