Protein Katabolism. 



529 



The marked decrease in the nitrogen excretion on the second and third days 

 with food shows a tendency of the body to adjust itself rapidly to the new 

 conditions of protein ingestion and it is worthy of note that on the third 

 day of experiment No. 74, after a prolonged draft upon body protein not only 

 during the fasting period but likewise during the first two days of food, the 

 body was nearly in nitrogen equilibrium on but 6.37 grams of nitrogen. It is 

 greatly to be regretted that this experiment was not continued with the inges- 

 tion of small amounts of protein and the nitrogen balance further studied. 

 In subsequent fasting experiments this point will be taken into consideration. 

 During the period, then, with low nitrogen intake there was a marked tendency 

 for the body to adjust itself to new conditions and retard the great drafts upon 

 body protein made during the fasting experiment. Further discussion of the 

 effect of the ingestion of nitrogenous material upon the total katabolism of 

 protein is taken up in connection with the data for the nitrogen metabolism 

 experiments. 



'Protein Jcatabolized in metabolism experiments with food. The ingestion 

 of protein after fasting generally results in a diminution in the katabolism of 

 protein. The course of the protein metabolism has already been indicated in 

 discussing the income and outgo of nitrogen (table 251), and the actual 

 amounts of protein katabolized in the food experiments are recorded in table 

 252. 



Taele 252. Protein katabolized per kilogram of body-weight in metabolism 



experiments with food. 



A comparison of the results given in this table with table 226 for experi- 

 ments without food shows that in experiment No. 70, the protein katabolized 

 on the first day with food was practically the same as that on the last fasting 

 day. But on the second and third days the katabolism of protein decreased to 

 that of the first day of the fast. In experiment No. 72 with S. A. B. the pro- 

 tein katabolized on the first day with food was essentially the same as that on 

 34 



