ii THE THEEMIC ECONOMY OF THE OBGANISM 69 



Since the normal variations in temperature persist even during 

 fasting, and when the temperature of the environment is kept 

 uniform, we must conclude that they are independent of nourish- 

 ment and changes of external temperature. 



At first sight it seems reasonable to ascribe the hyperthermia 

 of the day to muscular activity, which is undoubtedly always 

 greater by day than by night. If, however, the course of the 

 curve be considered, we shall find this theory to be inadequate, 

 since the hours during which the temperature rises do not 

 coincide with increased muscular work, and those during which 

 it falls do not correspond with a gradual decrease in muscular 

 activity. Moreover, Jtirgensen's curve was obtained in an in- 

 dividual who remained in bed the" whole twenty -four hours ; the 



P.M. A.M. P.M. 



7 8 9 10 11 12 1 2 34 5678 9 10 11 12 1 2 34 5 5 " 

 37,6 

 37,4 

 37,2 



36.4^ 



FIG. 14. Daily variations in the temperature of the body when fasting and at rest, obtained by 

 the bolometrical method. (Benedict and Snell.) 



curve of the variations, therefore, does not appear to be explained 

 as the result of muscular activity and rest. 



In default of other explanation, the daily variations in tempera- 

 ture may be regarded as due to an automatic variation in the regula- 

 tion of temperature by the nervous system. In the morning the 

 temperature of the body is regulated for 36'5, in the evening 

 for 37-5. 



" II me parait evident (writes 0. Eichet) que le systeme nerveux 

 traverse dans le cours d'une periode de vingt-quatre heures des 

 phases d'excitation et de depression, qui se traduisent par un 

 niveau variable de regulation thermique." l Just as in psychic 

 life there is a period of wakefulness and a period of sleep, so in 

 organic life there is normally a period of hyperthermia and one 

 of hypothermia, independent of the hours of meals, the external 

 temperature, the latitude, etc., and dependent upon the positive 

 and negative variations in the functional tone of the nervous 



1 "It appears to me evident that the nervous system passes in the course of a 

 period of twenty- four hours through phases of excitation and depression which are 

 shown in a variation in the levels at which the temperature is regulated." 



