Comparative Mijohgy of the Chimpanzee. 363 



the wrist or hand will become the flexora^ and vice versa, 

 and the contijTuous segments will be flexed in opposite di- 

 rections. Daring the earlier foetal periods the hand is in a 

 state of supination, and afterwards becomes pronated, re- 

 maining so through life in the common Quadrupeds, only 

 some, as the higher Carnivora, the Quadrumana, and espe- 

 cially man, having the power of freely rotating it back 

 to its original condition, which, of course, is more likely to 

 illustrate the true morphology than any afterwards ac- 

 quired. Therefore, the muscles on the front of the fore- 

 arm attached to the wrist are morpholog-icalf// extensors, 

 although they will probably retain the functional name 

 o? flexors, since by their contraction they shorten the limb. 

 In the leg of man, the above rule obtains even as to the 

 slight lateral deflection at the joints, for the hip stands 

 outward, the knee inward, and the ankle again outward, 

 so that the sole of the foot may be inverted more easily 

 than everted, as is more strikingly shown by the perma- 

 nent condition of the foot in the ape, in whom, however, 

 the rule is infringed by the peculiar outward curvature of 

 the whole limb for greater facility in climbing. So when 

 the arm is placed in the position indicated above, the 

 shoulder stands outward, the elbow inward, and the wrist 

 again outward, the hand bending more naturally to the 

 ulnar than to the radial side ; and accordingly we find the 

 Flexor carpi idnaris more powerful than the Flexor carpi 

 radialis, and the hand of the Bird is permanently flexed to 

 the ulnar side. The use of the " antero-posterior symme- 

 try" betvv^een scapula and ilium, humerus and femur, fore- 

 arm and leg, in the common Quadrupeds, for better bal- 

 ancing the body when at rest, is evident; but since the 

 animal when moving goes forward, the hand is pronated 

 so that the two lower segments, which are often much 

 elongated, both bend backward, aflbrding a more extensive 

 motion in that direction for propelling the body forward. 

 But in the hind leg the segments below the knee, and in- 



