186 Metabolism of Healthy Max. 



ratios being given in the last column. The ratios vary from 100:112 with 

 the subject H. E. S., to 100 : 155 with the subject W. 0. A. On the average 

 the ratio was 100 : 130, a ratio somewhat less than that found for the ratio 

 between the carbon dioxide during sleep and during waking hours. The chief 

 significance of the ratio is to indicate that the oxygen absorbed is considerably 

 greater during waking hours than during the sleeping hours. The significance 

 of the oxygen consumption when awake and when asleep must be left for dis- 

 cussion in another portion of this report. 



CONCLUSIONS WITH REGARD TO OXYGEN CONSUMPTION. 



As has been repeatedly implied in this discussion, the oxygen consumption 

 per se has been directly determined on man too rarely to have as yet a great 

 significance in the literature. The values obtained by the Zuntz-Geppert appa- 

 ratus and by Speck during short experiments have been used to calculate the 

 indirect calorimetry, and the results thus obtained have bad to take the place 

 of direct calorimetric measurements in much of the research in metabolism. 

 With the advent of the direct measurement of heat by a respiration calorimeter, 

 the necessity for the oxygen determination has not been felt so keenly, and in 

 the large number of experiments made with the Middletown respiration calo- 

 rimeter prior to 1905, the oxygen consumption was not directly measured. 

 Subsequent to that date, with the modified type of apparatus all four factors 

 of metabolism, namely, water-vapor elimination, carbon-dioxide production, 

 oxygen absorption, and heat production have been simultaneously measured. 

 With the heat production directly measured, the oxygen consumption has a 

 special value as indicating the nature of the materials katabolized ; by analyzing 

 the urine and feces, and thus obtaining the total nitrogen excretion, it is pos- 

 sible to compute with considerable accuracy the katabolism during any given 

 day and to apportion this katabolism among protein, fat, and carbohydrate. 



This method enables us for the first time to obtain an idea in regard to the 

 amount of carbohydrate, either in the diet or in body glycogen, which is con- 

 sumed or katabolized during a given time. The direct oxygen determination, 

 therefore, appears at the present time to be of the greatest value in indicating 

 the amount of glycogen entering into the metabolism. Heretofore it has been 

 necessary to assume that the carbon derived from material other than protein 

 has been carbon of fat, but with both the oxygen consumption and the heat 

 production directly measured, it is possible to apportion the katabolism with 

 great accuracy. This has already been of considerable use in studying the 

 fasting metabolism with man, 1 and it was there found that on the first day 

 of inanition the body glycogen drawn upon for the katabolism may amount 

 to 180 grams, and that on the second day of fasting there may likewise be a 

 heavy draft upon glycogen. 



1 Benedict, loc. cit. 



