CHAPTER XIV 

 THE REGULATION OF TEMPERATURE 



The energy liberated by the metabolic processes appears 

 as physiological activity and as heat. Of these the former 

 is a primary, the latter a secondary or incidental effect. 

 In cold-blooded animals the heat evolved is immediately 

 lost by conduction and radiation to the environment. 

 The temperature of these animals is therefore only shghtly 

 higher than that of the surroundiag medium. But heat, 

 while it is the result and not the cause of metabohc changes, 

 has a considerable influence upon the rate at which such 

 changes occur; the rate of metabohsm varying in cold- 

 blooded animals directly with the external temperature. 

 This is seen in the rise in CO2 output which in the frog 

 accompanies rise of temperature. In warm-blooded 

 animals there is developed a mechanism for the conserva- 

 tion of the heat produced by cell activity, in such a manner 

 that the temperature of the body is maintained at an 

 almost uniform level which is independent of and higher 

 than the usual temperature of the environment. Owing 

 to the rapidity of the circulation all the internal organs 

 are practically at the same temperature. 



The advantages of this arrangement are obvious. The 

 constancy of the temperature abohshes any dependence 

 of functional activity upon the environment, while its 

 tropical level is suitable for the rapidity of metabohc 

 changes. 



In man the body temperature, as usually taken, in the 

 mouth or axilla, is 36-9° C. (98-4° F.). A more accurate 



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