Metabolism Experiment No. 59. 33 



portion of the carbon dioxide in the ventilating air-current is absorbed in 

 the soda-lime cans or purifiers. The amount so absorbed is recorded in 

 column d. The amount exhaled by the subject, i. e., the amount actually pro- 

 duced during any period, is the algebraic sum of columns c and d. These 

 amounts are recorded in column e. Since the volumes of the carbon dioxide 

 are used in computing the respiratory quotients, they are calculated by multi- 

 plying the figures in column c by the factor 0.5091 and the results are recorded 

 in column /. Column g records the amounts of carbon in carbon dioxide 

 exhaled. These values are used in subsequent calculations affecting the gain 

 or loss of chemical elements in the body. 



When it is remembered that normal air contains from 3 to 4 parts of carbon 

 dioxide per 10,000, the data in column a of the table appear of peculiar 

 interest. The results serve to show that the carbon dioxide content of the 

 air in this experiment was iu general from 8 to 10 times that of normal air, 

 and in one instance, at 7 p. m., December 18, it reached more than 20 times 

 the normal. 



The amount of carbon dioxide remaining in the chamber at the end of each 

 period is determined simultaneously with the amount of water by absorbing the 

 carbon dioxide from the known volume of air passed through soda lime. The 

 ratio of the total volume of the sample to the volume of air in the calorimeter 

 chamber being known, the amount of residual carbon dioxide can be computed. 

 The amount of carbon dioxide, in parts per 10,000, can in all cases be roughly 

 approximated by multiplying the residual amount in grams of carbon dioxide 

 by 1.12, hence in subsequent experiments the ventilation conditions will not 

 be expressly tabulated. 



Oxygen Consumed. 



The role played by oxygen in katabolism is a complex one, in that all three 

 components of the body, namely, protein, fat, and glycogen, are oxidized in 

 the process of katabolism. The amount of oxygen absorbed during the oxi- 

 dation is of great importance in interpreting the kinds and amounts of body 

 materials oxidized. While in the case of carbohydrates oxygen is used to 

 oxidize only carbon, since hydrogen and oxygen in the carbohydrate molecule 

 exist in the proportion to form water, with fat and protein, on the other hand 

 there is oxidation of both carbon and hydrogen. Hence the ratio of the oxygen 

 consumed to the carbon dioxide exhaled is markedly different with the three 

 groups of compounds. 



For the proper interpretation, therefore, of the specific katabolism, a knowl- 

 edge of the amount of oxygen absorbed is essential. In these experiments the 

 amount thus absorbed is determined by noting the loss in weight of a steel 

 cylinder from which oxygen is admitted to the ventilating system from time 

 to time, and also any drafts upon the residual amount of oxygen in the air 



3 



