THE ANTERIOR LIMBS OF QUADRUPEDS. 61 



which reason urges, and which demand the 

 agency of the hand of man ? 



There is, however, still a modification of the 

 anterior limbs, in mammalia, to which we must 

 refer ; we mean their conversion into pad- 

 dles or oars for propeUing the body through 

 the water. We find this to be the case with 

 the seal; but the seal can also shuffle along on 

 the shore, or scramble over the surface of 

 rocks ; it has besides posterior limbs of a fin- 

 like character, placed completely at the ex- 

 tremity of the body. In the whales and por- 

 poises, on the contrary, there are no posterior 

 limbs, and the anterior pair are far more com- 

 pletely paddles in appearance and structure. 

 The bones are all imbedded in cellular tissue, 

 and a smooth oily skin envelopes the whole, 

 which is modelled into a short fiat flipper, 

 worked by muscles of great power and energ}% 

 There is in this instrument of aquatic pro- 

 pulsion not the slightest prehensile power; it is 

 not even destined as a support to the body, 

 but is merely fashioned as an oar; yet the 

 female whale, when alarmed, can press her 

 young cub between this paddle and her side, 

 while she dives to avoid the assaults of her 

 enemies. 



