220 



Metabolism of Healthy Man. 



ably accurate method of computing the total energy transformation. Unfortu- 

 nately the direct determination of oxygen requires apparatus fully as compli- 

 cated and nearly as difficult to manipulate as does the direct determination of 

 heat, and hence any relationship which may be established between the oxygen 

 consumption and the heat production can be of but little aid to physiologists in 

 general. These relationships are, however, of great importance in reviewing 

 work in which the carbon dioxide, oxygen, and heat are simultaneously deter- 

 mined and in ascribing to errors in the determination of carbon dioxide, oxygen. 

 or heat any discrepancies there found. This is clearly shown in a preceding- 

 publication, 1 where the carbon-dioxide thermal quotient and oxygen thermal 

 quotient, i. e., their calorific equivalents, were of incalculable value in indicating 

 with great accuracy the exact nature of the error in one or two experiments, the 

 results of which were otherwise inexplicable. 



Calorific Equivalents of Oxygen and Carbon Dioxide in Metabolism Experiments. 

 During sleep. The difficulties attending the direct determination of oxygen 

 in experiments of short i)eriods have been frequently pointed out, and it is 

 especially with experiments during sleep or during uniform muscular activity 

 that the best results were obtained. The calorific equivalents of oxygen and car- 

 bon dioxide for a number of individuals during sleep are presented in table 91. 

 Some of the results, namely, those with A. W. S., E. 0., and J. F. S., are drawn 

 from the experiments prior to the development of a method for the direct deter- 

 mination of oxygen and hence with these subjects, only the calorific equivalent of 

 carbon dioxide can be given. The calorific equivalent of oxygen during sleep 

 varies from 3.01 to 3.52, that is, for every gram of oxygen absorbed, there may 

 be from 3.01 to 3.52 calories of energy liberated. On the average of all experi- 

 ments, 3.37 calories of heat were produced for every gram of oxygen absorbed. 



Table 91. Calorific equivalent of oxygen consumed and carbon dioxide 

 eliminated for different individuals during sleep. 





1 For 6 nights. The calorific equivalent of carbon dioxide for 61 nights was 3.13. 



Examining the calorific equivalents of carbon dioxide, we find that they may 

 vary from 2.83 to 3.23, the average being 3.02. In considering the calorific 



1 Benedict, Carnegie Institution of Washington Publication No. 77, 1907, p. 513. 



