144 ANTHROPOID APES. 



or prehensile member — that is, of a hand, not modi- 

 fications of a foot resting firmly on the ground and 

 supporting the whole weight of the body. 



" It must not be forgotten that the structure of 

 the skeleton is subject to mechanical laws, which 

 may be traced through the whole series of the 

 animal world. This is readily apparent when we 

 turn to the human structure. 



" The human foot rests for the greater part of its 

 length on the ground, that is to say, with the heel 

 and centre of the foot, which form together a firm 

 arch. The tarsus consists of the astragalus, and 

 also of the os calcis, which in man form a very 

 prominent part, taking a backward and downward 

 direction, and of five other bones. The metatarsus 

 consists of five bones, on which the five toes are 

 inserted. In man these metatarsal bones are con- 

 siderably lunger than 4he separate phalanges. Thus, 

 the arch on which man is supported in an erect 

 position extends from the heel to the extremities 

 of the metatarsal bones. The several bones are 

 slightly movable, but they are so firmly connected 

 that they can diverge but little from each other, 

 unless muscular power is exerted. In order to press 

 the toes upon the ground, it is again necessary to 

 exert the muscles. The arched instep has this ad- 

 vantage, that the foot can take a better hold of the 

 slight inequalities of the ground. In a profile view 

 of the skeleton of a human foot, the shortness of 

 the toes, in comparison with the length of the 

 arched instep, is very apparent. In any natural 

 position, even when man is not walking or standing, 



