Anatomy of the Chimpanzee. 351 



extremities, a great tendency to become simplified. In man 

 they are undoubtedly most complicated ; in him also the move- 

 ments they perform are most varied." 



After the description and detailed comparison of the poste- 

 rior extremities of the Chimpanzee and other Mammifera, we 

 find the following considerations respecting these organs. 



" By this comparative description of the myology of the 

 posterior extremities, I think I have demonstrated that their 

 muscles become simplified in animals in proportion as we re- 

 cede from their perfection in man. And if we consider atten- 

 tively what is peculiar and distinctive in the organization of 

 these posterior extremities, we cannot doubt for a moment that 

 they are destined to support and move the body. It is for this 

 reason that the arrangement of their muscles is entirely dif- 

 ferent from that we have observed in the anterior extremities. 

 For while we see the force of flexion prevail over that of ex- 

 tension in the anterior extremities, we witness, on the con- 

 trary, that of extension prevail over flexion in the posterior 

 extremities. It is particularly in man that this fact is shewn 

 in the most conspicuous manner. We have only to compare 

 the development of the extensor muscles of the leg with that 

 of the flexor muscles, to be convinced of this, or, if we wish a 

 proof more conclusive still, we have but to examine the mus- 

 cles of the leg. It is principally to the great sti^ength of all 

 these extensor muscles that man owes the power of holding 

 himself erect and walking on two feet. We again find it, for 

 that same reason, in animals whose trunk is straight, and 

 whose movements are principally made with the hinder feet ; 

 the examples of the kangaroo and sloth prove this. I do 

 not add the example of the monkeys, because there is none 

 of them that can hold itself upright and walk without any 

 other support than the hinder feet. They are all quadrupeds, 

 with this modification, that the four feet are but ill fitted to 

 support and move the body on a horizontal plane, but rather 

 for making it ascend a vertical plane. The movement they 

 perform in the act of grasping is their trvie attribute. We have 

 only to notice the manner in which they grasp the bars of their 

 cage to be assm'ed of- this. Their feet are modified for the 

 purpose quite in a peculiar manner, as I have fully stated in 



