336 



THE MECHANICAL FUNCTIONS. 



rently corresponding to pelvic bones, for the presence of 

 which no more probable reason can be assigned than the 

 tendency to preserve an analogy with the more developed 

 structures of the same type. 



A similar adherence to the law 

 of uniformity in the plan of con- 

 struction of all the animals belong- 

 ing to the same class, is strikingly 

 shown in the conformation of the 

 bones of the anterior extremities of 

 the cetacea; for, although they pre- 

 sent, externally, no resemblance to 

 the leg and foot of a quadruped, being 

 fashioned into fin-like members, wdth 

 a flat, oval surface, for striking the wa- 

 ter, yet, when the bones are stripped 

 of the thick integument which covers 

 them and conceals their real form, 

 we find them, (as may be seen in Fig. 

 216) exhibiting the same divisions 

 into carpal and metacarpal bones, and 

 phalanges of fingers, as exist in the 

 most highly developed organization, 

 not merely of a quadruped, but also 

 of a monkey, and even of man. 



§ 3. */lmphibia. 



In the small tribe denominated by Cuvier Amphibia, and 

 consisting of the Phoca, or Seal, and the Tricheciis, or 

 Walrus, we perceive that an advance is made towards a 

 fuller development of the limbs: these animals having a dis- 

 tinct neck and pelvis, and both hind and fore extremities. 

 In the seal the hind legs are drawn out posteriorly to a con- 

 siderable length, and placed parallel to each other: when 

 united and alternately raised and depressed, they perform 



