Katabolism of Protein. 455 



stant throughout the fast, and according to the results of Brugsch (12), the 

 purin bodies remain constant, at least on the last 8 days of a 30-day fast. This 

 would imply that there was no excess in the excretion of extractive nitrogen. 

 The sulphur determinations are of value in suggesting the nature rather than 

 the total amount of the protein katabolized. 



But little satisfaction attends the attempt to designate the kinds and amount 

 of protein katabolized from the phosphorus output, for as has been shown in 

 discussing the phosphorus excretion, the ratio of nitrogen to phosphorus is very 

 much smaller than that occurring in the ordinary nucleo-proteins, which signi- 

 fies that in all probability phosphatic material of the bones has been drawn 

 upon and excreted. 



An attempt has been made to measure protein katabolism by means of the 

 chlorine excretion, assuming that the chlorine content of muscle is constant. 

 From the discussion of the chlorine output during fasting, it is apparent that 

 here again the results of the experiments are such as to preclude an accurate 

 comparison between the elimination of chlorine and the amount of protein 

 katabolized. Becent advances in the study of the significance of the partition 

 of nitrogen would imply that a knowledge of the purin bodies, amino-acids, 

 ammonia, and uric acid of the urine would furnish a much more accurate basis 

 for the computation of the total protein katabolism than would perhaps the 

 total nitrogen excretion. In the absence of more definite information regard- 

 ing the nature of the nitrogenous material excreted during fasting, the only 

 alternative is to follow the usual custom and to assume that the total nitrogen 

 output indicates the total protein katabolism. In table 226 the amounts of 

 protein katabolized per day, computed by multiplying the total nitrogen excre- 

 tion by 6.0 are recorded. There are considerable differences in the body- 

 weights of the subjects of these experiments, and consequently the amounts 

 per kilo of body-weight are also recorded for purposes of comparison. Since 

 there is a mass of evidence to show that muscular activity, at least when not 

 excessive, does not influence the nitrogen output, the uniformity or lack of 

 uniformity, between the total amounts of protein katabolized by different 

 subjects and on different days by the same subject can be better compared than 

 the katabolism of either carbohydrate or fat. 



An examination of the figures in the table shows that during inanition, the 

 protein katabolized on the first day of fasting varies from 35.0 grams to 79.5 

 grams. The average for the first day for the 14 experiments is 60.2 grams. 

 Aside from the extremely low amount on the first day of experiment No. 71, 

 the lowest result for the first day is 46.7 grams. On the basis of per kilo of 

 body-weight, the fluctuations for the first day of the fast range from 0.61 to 

 1.44 grams, averaging 0.94 gram. The variations from the average protein 

 katabolism per kilogram of body-weight indicate that there is no approach to 

 uniformity in the results obtained on the first day without food. 



