THE WHALE TRIBE. 109 



while that of the fish moves laterally. Some of its mo. 

 tions, however, are oblique, and not wholly vertical. It 

 is with the tail, as in the case of fishes, that the Whale 

 mostly swims, the flippers answering the purpose chiefly 

 of balancers. When the Whale is killed he turns over on 

 his back, showing that it is by the action of the flippers 

 that he keeps in his ordinary position. Though the Whale 



has neither hands nor feet, 

 yet the frame-work of the 

 flippers is much like that of 

 a hand, as may be seen in 

 Fig. 92, representing a flip- 

 per, and also its bones un- 

 covered. The immense pow- 

 er of the tail in swimming 

 can be judged of by its 

 breadth, which often is 20 



Fig. 92. Flipper of the Whale. feet. 



186. The skin of the Cetacea is very peculiar. In other 

 animals which have much fat, it is accumulated beneath 

 the skin ; but in the Whale the skin is enormously thick, 

 and has the fat mingled with its fibres. It is this mix- 

 ture of skin and fat which is called blubber. This is 

 sometimes two feet thick, and weighs in some cases 30 

 tons ; and yet, it being lighter than water, it helps to buoy 

 up the monstrous body. When stripped of its blubber 

 the Whale sinks at once. The mingling of the fat with 

 the skin has two objects. One is to enable the Whale 

 to keep its blood warm in the cold water of the frigid 

 regions, fat being one of the best non-conductors of heat, 

 and therefore serving to keep the heat in the body. The 

 other is to enable the animal to bear the immense press- 

 ure of the water when it goes down to great depths. 



187. Although the Whale has lungs, like terrestrial an- 

 imals, it can stay under the water for a long time. It has 

 a peculiar provision enabling it to do this. This I will 

 explain. In the " First Book in Physiology" I showed 



