88 



ZOOLOGY. 



with ice ; the quantities of ice dissolved will give the amount 

 of the difference, whirh is enormous; for, alter thnv hours, 

 the heat produced by the fish will scarcely have acted on the 

 ice, whilst that originating from the rabbit will have pro- 

 duced more than a quart of water. Now the amount of heat 

 required to convert so much ice into water will be found 

 equal to that necessary to raise the temperature of three 

 quarts of water from the freezing to the boiling point. 



Hence the distinction of animals into cold and hot blooded. 

 In man the heat of the skin varies from 97 to 100 Fahr. ; 

 that of the interior of the body is always 100. It is the 

 same in most mammals. In birds the temperature rises to 

 108. The blood in both is hotter. 



Fig. 54. The Marmot. 



175. In general, birds and mammals maintain the same 

 temperature at all seasons of the year and in all climates ; 

 but there are some in which the temperature lowers as winter 

 proceeds; these are the hybernating animals, such as the 

 marmot (Fig. 54), the bat, and hedgehog. 



176. In the young, the production of animal heat is not 

 equal to what it afterwards becomes, especially in those born 

 with the eyes closed. Thus kittens or puppies left exposed 

 to the air, even in summer, soon die. New-torn children also 

 are extremely susceptible of cold. 



177. This production of animal heat is evidently con- 

 nected with the phenomenon of vital combustion, with the 

 absorption of oxygen by the blood, and the production of car- 

 bonic acid gas. It seems, in fact, to be proportional to the 

 amount of oxygen absorbed, and hence is greatest in birds 

 and mammals. 



