68 



PHYSIOLOGY 



CHAP. 



temperature of the day is considerably greater, and may be as 

 much as l-l-5. 



More accurate are the curves obtained by Benedict and Snell 

 for a student 20 years old, who, during the whole period of 

 observation, was shut up in Atwater's calorimetric chamber, in 



P.M. A.M. 



7 8 9 10 11 12 1 2 34 



6 7 



P.M. 

 Q 10 11 12 1 2 3 



456 



36.6 



FIG. 12. Variations in temperature during two days spent at rest in bed (Jiirgensen) : A, on the 

 ordinary diet ; B, when fasting. 



a uniform temperature of 19. The determinations of the bodily 

 temperature were carried out by the bolometrical method, and on 

 an average every twelve minutes. Fig. 13 shows the curve of the 

 daily variations of temperature during rest and on a diet, Fig. 14, 

 those during fasting, all other conditions remaining unaltered. A 



P.M. A.M. 



7 8 9 10 II 12 1 2 3 4 



P.M. 

 8 .9 10 11 12 1 2 3 4 5 fr 



Fio. 13. Daily variations in the temperature of the body during rest and on the usual diet, 

 obtained by the bolometrical method. (Benedict and Snell.) 



comparison of the two curves shows that the general course of the 

 variations is the same ; but the range in the former curve is 0*93, 

 in the latter 1'18. 



These variations prove that the thermic regulation of man, and 

 of homoiothermic animals in general, is not as perfect as that of a 

 thermostat. On what do the hypothermia of the night and the 

 hyperthermia of the day depend ? 



