GENERAL STRUCTURE OF MAMMALS. 91 



them); and the Whale tribe are adapted in their general 

 form to lead the life of fishes (among which they are still 

 commonly ranked by persons ignorant of natural history). 

 Notwithstanding these marked differences in external form, 

 there is a great correspondence as to internal structure ; for 

 bats and whales, as well as ordinary quadrupeds, produce 

 their young alive, and suckle them afterwards ; they are also 

 warm-blooded, breathing air, and having an active circulation. 

 The bodies of Mammals are, for the most part, more or less 

 completely covered with hair, which serves to keep in their 

 warmth ; and this is seldom absent, except in such as inhabit 

 warm climates and do not require this provision. In the 

 Whales, the same end is answered by the thick layer of oil in 

 the substance of the skin, constituting the blubber ; and Man 

 is left to form a protective covering for his body by the exer- 

 cise of his own ingenuity. The general arrangement of the 



Sub-maxillary Gland Parotid Gland 



Windpipe .. ~"*v.. 



' 



Pharynx 



-Oesophagus 



Gall-Bladder 



Colon .^, _ 

 Caecum.... 

 Small Intestines 



Fig. 30. INTERIOR OF A MONKEY. 



internal organs of Mammals will be seen from the accom- 

 panying figure of the body of a Monkey, laid open in such 



