LIBRARY OF NATURAL HISTORY 



VOL III 



MAMMALS 



CHAPTER XXIX 

 CETACEANS ORDER CETACEA 



UNDER the general title of Cetaceans may be included the whole of those Mam- 

 mals commonly known as whales, porpoises, and dolphins, which differ from all 

 hitherto described in their assumption of a fish-like form, and their complete adap- 

 tation to a purely aquatic mode of life. Indeed, so like are Cetaceans in their gen- 

 eral outward appearance to fishes, that they are commonly regarded as belonging to 

 that class. In all essential features of their organization they are, however, true 

 Mammals, breathing atmospheric air by means of lungs, having warm blood, a four- 

 chambered heart, the skull articulating with the first joint of the back bone by 

 means of two condyles, and the cavity of the body divided into two chambers by a 

 midriff; while they produce living young, which are nourished by milk drawn from 

 the bodies of their mothers. 



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