194 THE REASON WHY 



" And one of them I saw myselfe sunke downright with the 

 abundance of water that this monstrous fish spouted, and filled 

 it withall." HOLLAND. 



nmosphere ; so that these animals are obliged to come occasionally to the surface 

 to breathe. Thus the function of respiration is conducted on a plan entirely 

 different in these two groups. 



Ayain, the heart of the fish has only two cavities, and the blood does not return to 

 tt after passing through the gills, but is immediately distributed to the body ; whilst 

 the heart of the whale has four cavities, and the blood returns to it after passing 

 through the lungs. Hence, the plan of circulation also is entirely different in the 

 two classes being single in the one and double in the other. 



Again, the blood of the fishes is cold, and that of the whale is warm ; another 

 character of great importance, in regard to the relative activity of the vital opera- 

 tions in general, in these two classes respectively. 



Further, fishes are oviparous, propagating by eggs, from which the young come 

 forth in due time, with little or no attention on the part of the parent ; whilst 

 whales are vivaporoits, producing their young alive, and nourishing them afterwards 

 by suckling, precisely as other mammalia. 



581. By what means is the whale enabled to eject water in 

 the form of a spout ? 



The apparatus by which this is accomplished, consists of two 

 pouches or reservoirs, situated beneath the nostrils, and communi- 

 cating with the back of the mouth by the usual nasal passage, 

 which is furnished with a valve. 



When the animal wishes to eject water contained in its mouth, 

 it moves its tongue and jaws as if about to swallow the fluid ; but 

 by closing the pharynx, it compels the water to ascend through the 

 nasal passage, the valve of which it forces open, and also distends 

 the reservoirs. There it may be retained until the animal wishes 

 to eject it ; and this is effected by a forcible compression of the 

 pouches, which compels the water to escape by the nostrils ; its 

 return to the mouth being prevented by the valve just mentioned. 



582. What provision have whales for the retention of their 

 internal heat ? 



The whale tribes have smooth and polished skins, which do not 

 readily throw off the heat ; underneath these, there is a large 

 deposition of oily fat, which is a very bad conductor of caloric. 



