ANIMAL HEAT. 171 



PART IV. 



ANIMAL HEAT. 



CHAPTER I. 



Internal Heat of living Bodies usually greater than the Heat of sur- 

 rounding dead Matter. Whales and Porpoises in the Arctic 

 Ocean as warm as at the Equator. Man's Heat does not vary 

 in Extremes of Temperature. Blagden's Experiment. Natural 

 Tendency to Equilibrium of Heat in all dead Matter. Living 

 Matter sustains its own Heat. 



399. IT is easy to see that the temperature of most ani- 

 mals is higher than the surrounding medium. Our own 

 bodies are usually warmer than the air about us. In winter, 

 especially, when water freezes and the air is colder than ice, 

 this fact is to be noticed. If we then lay our hands upon 

 the body of a horse or a kitten, or upon our own flesh, we 

 find them to be warmer than the air. If we take ice into 

 our hands, it* melts, from the natural heat of our flesh ; and 

 yet this flesh is not cooled down to the coldness of ice, and, 

 although it loses a little heat while it is in contact with the 

 ice, it soon recovers it after the ice is taken away. 



400. The porpoise and the whale dwell under the ice, in 

 the waters of the Northern Ocean. Above them, the air may 

 be cooled down to 50 below freezing point ; the temperature 

 of the ice is at least as low as 32, and the water is nearly 

 as cold, and yet they are warm. Their temperature is sus- 

 tained at about 100, as high as that of other animals of the 

 same kind, in the burning regions of the equator. 



401. Man dwells in all climates; he finds a home in 



