CHAPTEE IX. 



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 armpit the 

 most convenient situation, under ordinary circumstances, for examina- 

 tion by the thermometer the average temperature is 98.6 F, (36.9 0.). 

 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 main- 

 taining uniformity 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; 

 Climate and Season ; Food and Drink. 



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

 1 F. (.54 0.) above that of 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. 



Sex. The average temperature of the female is very slightly higher 

 than that of the male. 



Period of the Day. The temperature undergoes a gradual alteration, 



