Comparative Myology of the Chimphnzee. 375 



small on the right side of this Chimpanzee ; it was present 

 in those of Vrolik and Tyson, but absent in that of Traill, 

 in the Gorillas of Wyman and Duvernoy, and in the lat- 

 ter's Orang, in the Howling-Monkey and Ateles Paniscus. 

 Not constant in the Cynocephali. 



In man the Glutcei and long flexors of the leg have two 

 sets of functions according as they take their fixed point 

 from above or from below, that is, as they are used either 

 for moving the legs by themselves as mere appendages, or 

 for acting powerfully upon the trunk as in locomotion, 

 and maintaining the erect position on one or both legs. 

 In the ape, these positions not being required, the muscles 

 are employed in locomotion and in leaping as we have 

 seen above, but chiefly for moving the prehensile limb 

 with any object which may be in its grasp ; they are 

 therefore modified not so much in size as in position, in 

 which latter respect we remark the evidence as to the in- 

 tended semi-erect attitude of these animals. With the 

 Gastrocnemius and Soleus the case is otherwise. They 

 also perform two different functions according as they act 

 from above or from below ; but in man their great strength 

 is almost wholly employed after the latter manner, for 

 raising and balancing the body upon the foot, while the 

 movements of the foot on the leg are limited, and require 

 little power. The body of the ape is not designed to be 

 balanced upon the foot in his usual attitude, and in walkr 

 ing he lifts the foot as a part of the leg without much mo- 

 tion at the ankle. So in the ape the Gastrocnemius and 

 Soleus are much more slender than in man, but their mus- 

 cular portion is longer, in adaptation to the less powerful 

 but more extensive and free movements of the prehensile 

 foot. In most Quadrupeds, again, which rest on the ends 

 of the toes or metatarsal bones, these muscles must be 

 powerful like the extensors of the other segments of the 

 limb. Thus we see that the semi-erect attitude of the ape 



