CHAPTER X. 



ANIMAL HEAT. 



THE Average Temperature of the human body in those internal parts 

 which are most easily accessible, as the mouth and rectum, is from 98*5 

 to 99-5 F. (36-9 37'4 C.). In different parts of the external surface 

 of the human body the temperature varies only to the extent of two or 

 three degrees (F.), when all are alike protected from cooling influences; 

 and the difference which under these circumstances exists, depends chiefly 

 upon the different degrees of blood-supply. In the arm-pit the most 

 convenient situation, under ordinary circumstances, for examination by 

 the thermometer the average temperature is 98 '6 F. (36 '9 C.). In 

 different internal parts, the variation is one or two degrees; those parts 

 and organs being warmest which contain most blood, and in which there 

 occurs the greatest amount of chemical change, e.g., the glands and the 

 muscles; and the temperature is highest, of course, when they are most 

 actively working: while those tissues which, subserving only a mechanical 

 function, are the seat of least active circulation and chemical change, are 

 the coolest. These differences of temperature, however, are actually but 

 slight, on account of the provisions which exist for maintaining uniform- 

 ity of temperature in different parts. 



Circumstances causing Variations in Temperature. The 

 chief circumstances by which the temperature of the healthy body is influ- 

 enced are the following: Age; Sex; Period of the day; Exercise; Cli- 

 mate and Season; Pood and Drink. 



Age. The average temperature of the new-born child is only about 1 

 F. (-54 C.) above that proper to the adult; and the difference becomes 

 still more trifling during infancy and early childhood. The temperature 

 falls to the extent of about -2 -5 F. from early infancy to puberty, and 

 by about the same amount from puberty to fifty or sixty years of age. In 

 old age the temperature again rises, and approaches that of infancy; but 

 although this is the case, yet the power of resisting cold is less in them 

 exposure to a low temperature causing a greater reduction of heat than in 

 young persons. 



The same rapid diminution of temperature has been observed to occur 

 in the new-born young of most carnivorous and rodent animals when they 

 are removed from the parent, the temperature of the atmosphere being 



