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 
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 along time. It has 
a peculiar provision enabling it to do this. This I will 
explain. In the “ First Book in Physiology” I showed 
