484 



CETACEA. 



not unfrequently do, to considerable depths, their 

 bodies are subjected on such occasions to enormous 

 pressure, to sustain which their body is enveloped in 

 a covering that possesses great elasticity. Their skin 

 is greatly thickened and made up of a texture of in- 

 terwoven fibres, enclosing an immense quantity of 

 oil or blubber, thus forming an integument admirably 

 adapted to resist compression. This thick blanket 

 of fat, moreover, retains the vital warmth, and thus 

 enables the Cetaceans to inhabit even the coldest 

 regions of the ocean. Being lighter than water, it 

 also greatly contributes to the buoyancy of these un- 

 wieldy animals. A dead whale floats ; but the car- 

 case, when stripped of the blubber, sinks imme- 

 diately. 



The Cetaceans are divisible into two sections. 

 Those having a head of ordinary proportions when 

 compared with the size of their body, and those in 

 which the head is of enormous dimensions. The first 

 of these will include the Dolphins and the Narwhals ; 

 the second, Whales, properly so called. 



The Dolphins (Delphinus) have teeth both in the 



FlG. 41.1. DOLPHIN. 



