CHAPTER XIV. 

 ANIMAL HEAT AND FEVER. 



In considering the problem of animal heat, it is essential to 

 bear clearly in mind the distinction between amount and inten- 

 sity of heat. The former is measured in calories (see p. 84), 

 and the latter in degrees of temperature. To measure the tem- 

 perature of a man a maximal thermometer with the Fahrenheit 

 or Centigrade scale is placed in some protected part of the body, 

 as the mouth, the axilla or the rectum. It is found by such meas- 

 urement that the temperature varies according to the site of ob- 

 servation and the time of day. It varies between 36.0 C. 

 (96.8 F.) and 37.8 C. (100.0 F.) in the rectum ; between 36.3 

 C. (97.3 F.) and 37.5 C. (99.5 F.) in the axilla; and between 

 36. C. (96.8 F.) and 37.25 C. (99.3 F.) in the mouth. These 

 variations indicate that the temperature is higher in the deeper 

 than in the superficial parts of the body ; in other words, that 

 the visceral blood is warmer than that of the surface of the body. 

 The variations of temperature, due to the time of day, are most 

 evident when it is taken in the rectum, and they amount in health 

 to a little over 1 C. or a little below 2 F., the highest tempera- 

 ture occurring about 3 p. m., and the lowest about 3 a. m. This 

 is called the diurnal variation and it may become much greater 

 in febrile diseases. 



Animals whose temperature behaves as above described are 

 called warm-blooded in contrast to other animals, called cold- 

 blooded, in whom it is only a degree or two above that of the 

 air, with which it runs parallel. Such animals include fishes, 

 amphibians, snakes, etc. Between the cold and the warm-blooded 

 animals is a group in which the animal is warm-blooded in sum- 

 mer and cold-blooded in winter. These are the hib< muling ani- 

 mals, such as the hedgehog, the marmot, the bat, etc. In this 

 connection it is interesting to note that the human infant be- 



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