20 Metabolism of Healthy Max. 



In the calculation of the total katabolism, in experiments where the oxygen 

 determinations are unsatisfactory, it is customary to assume that the total 

 carbon elimination, other than the carbon from protein, is derived from fat. 

 Since, however, the total amount of carbohydrates ingested in this diet was 

 small and can be found with reasonable accuracy, it is perhaps not erroneous 

 to assume that these carbohydrates were completely absorbed. 



As the katabolism shows subsequently that there was a marked draft upon 

 the body-material even under these conditions, we are correct in assuming that 

 in all probability the total carbohydrates ingested were burned, and the chief 

 question is whether the draft upon the body-material was met by the supply 

 of glycogen or was wholly fat. From the experience with a large number of 

 fasting subjects, it was found that on the first day of inanition there may be 

 as high as 180 grams of glycogen broken down in the body. On the other 

 hand, the subject of the experiment here reported actually stored glycogen on 

 the first 2 days of a 3-day experiment 1 nearly identical with this experiment 

 in plan. The muscular activity, body-weight, nature and amount of diet all 

 being the same in both cases, it is not unreasonable to assume that he actually 

 stored carbohydrates during this day. This possible, if not probable, storage 

 of glycogen may be assumed as equal to 21 grams for the 24 hours, i. e., an 

 average of the storage on the first 2 days of the experiment referred to above. 

 Under these conditions the calculation of the total katabolism becomes some- 

 what complicated. 



For the calculation of the total katabolism, then, the following data are 

 available : 



Grams. 

 Carbon dioxide as determined in respired air from 7 a. m. to 7 a. m. = 655.5 

 Nitrogen in urine from 7 a. m. to 7 a. m = 6.45 



From these two factors and the assumed storage of 21 grams of glycogen it is 

 possible to compute with considerable accuracy the total katabolism. 



Katabolism of protein. The protein is commonly determined by multiplying 

 the nitrogen excreted in the urine by the factor 6.0. In this experiment, there- 

 fore, the excretion of nitrogen corresponds to the disintegration of 38.7 grams 

 of protein. 



Katabolism of carbohydrate and fat. In addition to the carbon of carbon 

 dioxide expired, there is a certain amount of carbon in the urine. The ratio 

 of carbon to nitrogen has frequently been determined with normal healthy 

 men, and fortunately we have the average of the 3-day experiment made subse- 

 quently with this subject in which it was found that for every gram of nitrogen 

 there was 0.879 gram of carbon in the urine. Hence, in this experiment, with 

 the excretion of 6.45 grams of nitrogen there would probably be the equivalent 

 of 6.45 X 0.879 or 5.67 grams of carbon in the urine. 



In the carbon dioxide exhaled there are 178.8 grams of carbon. The total 

 excretion of carbon for the day, therefore, corresponds to 178.8 grams excreted 



1 Benedict and Milner, hoc. cit., p. 93. 



