BASAL METABOLISM. 



95 



TABLE 36 (continued). Nitrogen excreted in urine during experiments without food. 



(Amounts per hour.) 



'Subject was without food in first 3 hours of the 5 hours covered by the sample in each case. 

 Sucrose was given at the end of 3 hours. 



GENERAL CONCLUSIONS REGARDING 8-HouR EXPERIMENTS IN BOSTON. 



With the shortening of the experimental period, the distinction 

 between heat production and heat elimination becomes of considerable 

 consequence. In the 24-hour experiments it was found that the heat 

 production and heat elimination were essentially identical that is, 

 that the body-temperature as determined by rectal measurements was 

 practically the same each morning at 7 o'clock when the experimental 

 day ended. While the correctness of this assumption as a generaliza- 

 tion may fairly be questioned, nevertheless very considerable differ- 

 ences in body-temperature may actually appear and yet not affect the 

 calculation of the total heat production when based on the 24-hour unit. 

 With short periods, on the other hand, temperature fluctuations may 

 normally be expected. It has been demonstrated that there are ordi- 

 narily variations of 1 to 2 C. in the normal rectal temperature, the 

 minimum appearing from 3 to 5 a. m., and the maximum in the late 

 afternoon. Even during short periods of rest there may be consid- 

 erable fluctuation in the body-temperature. Consequently, as the 

 experimental period is shortened, there is an increasing danger of 

 possible error in the measurements of the heat production owing to 

 either a storage of heat in the body, as shown by an increase in the 

 body-temperature, or a loss of heat, as indicated by a fall in the body- 

 temperature. To obtain the true heat production, the values for this 

 storage or loss should be added to or deducted from the values obtained 

 for the heat actually eliminated during the period. 



This question is of special significance when the attempt is made to 

 compare the heat production and the gaseous exchange in other 

 words, to compare the direct and indirect calorimetry the difficulties 

 lying for the most part in securing a proper measurement of the body- 



