240 ANIMAL HEAT. 



The temperature of young animals is lower than of adults, or 

 rather they maintain a peculiar temperature much less, are more 

 easily cooled and heated, and they vitiate the air less, and re- 

 quire respiration less, proportionally, than adults. h As they 

 proceed to vitiate it more, and require respiration more, their ca- 

 lorific power increases. While their calorific powers are weak, 

 they breathe, if they are exposed to cold, more quickly, so as to 

 keep up their temperature as much as possible. 1 The same we 

 shall find is true of adult warm-blooded animals, not of the hyber- 

 nating family, when exposed to cold. 



Dr. Edwards found that habit has great influence on the calo- 

 rific powers of animals ; that a given low artificial temperature 

 in winter will reduce the animal heat much less than in summer k : 

 and that, with the habit of evolving more heat in winter, is ac- 

 quired the habit of consuming and requiring more oxygen, so 

 that animals supplied with a given quantity of air, and placed in 

 a given warm temperature in winter, die much sooner than in 

 summer. 1 Yet the momentary application of heat or cold has a 

 different effect : the former heating less if the body has been sub- 

 jected to a low, and the latter cooling less if the body has been 

 subjected to a high, temperature. We all feel the cold less 

 quickly on leaving the house in winter if well warmed first, than 

 if we leave it already chilly. 



When animals hybernate, their temperature falls, and respira- 

 tion is nearly or entirely suspended. m Their consumption of air 

 lessens as the temperature falls, whence they consume less in 

 November than in August. n If hybernating animals, while torpid 

 and still placed in the same temperature, are stimulated mecha- 

 nically to breathe, their temperature rises with the progress of 

 respiration. 



If the cold to which they are exposed is so intense that it 

 threatens death, it actually no longer depresses respiration, but, 

 for a time, excites it, and their temperature rises proportion- 



h Dr. Edwards, 1. c. p. 165. sqq. i 1. c. pp. 299. 310. 



k 1. c. p. 162. sqq. 252. sqq. ' 1. c. p. 200. sqq. 



m Spallanzani, Mtmoires sur la Respiration, p. 77. De Saissy could not by 

 cold produce torpor in a marmot, till he had deprived it of fresh air. Edwards, 

 1. c. p. 154. 



B M. de Saissy. See Edwards, 1. c. p. 286. 



M. de Saissy. See Edwards, 1. c. p. 305. 



