376 CETACEA. 



top of the head, so that the animal can respire when only 

 that portion is above water. It is evident, however, that 

 it could not breathe thus when its mouth was full of water 

 unless a peculiar arrangement was provided for the pur- 

 pose. This is effected by the upper extremity of the 

 wind-pipe being prolonged into a sort of cone or funnel, 

 which reaches up into the posterior part of the nares, 

 where it is firmly clasped by the surrounding soft parts. 

 Thus there is a completely closed passage from the blow- 

 hole to the lungs, and even when the animal is dashing 

 open-mouthed through the water in pursuit of its prey, 

 it can breathe whenever the top of its head is above the 

 surface. 



The outer skin of the Cetaceans is smooth and shining, 

 and is totally devoid of hair, only a few bristles being 

 sometimes present about the lips. On the back a com- 

 pressed adipose " dorsal-fin " is very often developed, 

 while the extremity of the tail is expanded into an 

 extremely broad and powerful " caudal-fin," which is 

 invariably horizontal, and not vertical as in Fishes. It 

 is the principal organ of locomotion, and in the larger 

 species is of enormous extent, so as to command sufficient 

 power to drive their huge bulk through the water at a 

 great velocity. 



Under the skin lies a thick coating of fat or " blubber " 

 of a peculiarly dense and elastic texture, and adhering 

 closely to the integument, of which, indeed, it was 

 formerly believed to be a modification. This blubber, 

 which yields the oil for which the larger Whales are so 

 relentlessly pursued by man, is not less useful to the 

 animal itself, serving not only to preserve the heat of the 

 body, but also to reduce the weight of its mighty bulk 

 and to bring it nearer to the specific gravity of the water 

 in which it exists. 



