218 Metabolism of Healthy Max. 



hand, while it has been conclusively demonstrated that the indirect calorimetry 

 in experiments of 24 hours' duration agrees perfectly with the direct calorim- 

 etry, we do not feel that the results obtained for 2-hour experiments are suffi- 

 ciently accurate to warrant a comparison of the two methods, direct and indirect 

 calorimetry. For such a purpose a special research is necessary, and, indeed, 

 such a research is now in progress in the Nutrition Laboratory. 



The results given in the tables in connection with this report are in such 

 detail that it is perfectly possible and feasible to compute the indirect calorim- 

 etry, assuming in most instances, however, a relatively constant nitrogen excre- 

 tion which has been found to be nearly the same with most individuals. 



The respiratory quotient, then, has in this series of experiments no particular 

 significance, other than to indicate in a general way the nature of the average 

 diet of man under the conditions existing at the time these experiments were 

 made. Apparently, therefore, the diet of the majority of the subjects contained 

 relatively large amounts of fat with a relatively small proportion of carbo- 

 hydrate. On the other hand, it must not be lost sight of that many of the 

 experiments here included were made during the night when digestion had 

 ceased and, indeed, some of them during the first day of fasting, and many 12 

 hours after the last meal, so that the tendency of a part of these experiments 

 would be to distinctly lower the average respiratory quotients. 



RELATION BETWEEN THE OXYGEN CONSUMPTION, THE CARBON-DIOXIDE 

 ELIMINATION AND THE HEAT PRODUCTION. 



In many of the earlier forms of respiration apparatus by which only the 

 carbon-dioxide elimination could be determined, it was the custom to compute 

 the energy transformations from the carbon-dioxide production, with due cor- 

 rection for the nitrogen in the urine. On this basis, it was assumed, after 

 making clue allowance for the carbohydrate in the diet, that the carbon not 

 combined with the nitrogen in the form of katabolized protein was carbon of 

 katabolized fat. In fasting experiments, the carbon unassigned to protein was 

 invariably computed as carbon of fat, making no allowance whatever for the 

 draft upon body glycogen. The error in this method of computation has been 

 pointed out in a previous publication. 1 In experiments where mixed diets or 

 diets of known character were administered, it was always assumed that the 

 carbohydrate of the diet was first completely oxidized and then the remaining 

 metabolism was ascribed to fat. While this method of computation certainly 

 serves to indicate in a general way the total heat production in an experiment, 

 obviously, factors founded on more substantial basis are highly desirable, and 

 in a number of the experiments made with the apparatus at Wesleyan Univer- 

 sity, the relationships between the carbon dioxide produced and the heat elimi- 

 nated have been carefully calculated. In certain of the experiments where the 

 oxygen was determined, the relationship between the oxygen absorbed and the 



1 Benedict and Milner, U. S. Dept. Agr., Office Expt. Stas. Bui. 175, 1907, p. 213. 



