Katabolism of Protein. 459 



days of fasting in the Middletown experiments the total amount of protein 

 katabolized was not far from 60 grams, corresponding to about 300 grams of 

 flesh. Assuming the whole protein katabolism to have resulted from katabol- 

 ized flesh about 1.2 grams of creatine would have been set free. 



The amounts actually found are much less than this theoretical quantity. 

 The absence of uniformity in the nitrogen-sulphur ratio points strongly to a 

 protein katabolism other than that of muscle. As the fast progresses this 

 ratio gradually approaches that of muscle protein. It is suggested, then, that 

 the true measure of flesh or muscle katabolized may in fasting man be the 

 amount of preformed creatine excreted in the urine. According to this 

 hypothesis the total protein katabolism on the first few days of fasting involves 

 little muscle protein, but as the fast progresses the muscle protein becomes dis- 

 integrated and releases creatine which is excreted unchanged. The muscle 

 katabolism does not comprise the total protein katabolism, for the creatine 

 excretion is practically constant on the fifth, sixth, and seventh days. The 

 nitrogen-sulphur ratio likewise becomes constant during these periods, and 

 the total amount of creatine excreted would correspond to that in but 125 grams 

 of katabolized flesh. There must be a continuous protein katabolism other than 

 that of flesh, which has reached a minimum on the fifth day. This suggestion 

 of the use of preformed creatine eliminated in the urine as an index of flesh 

 katabolized has at least the value of indicating many possible research problems. 

 Our experimental data are far too limited to bring the discussion out of the 

 field of speculation. 



Folin 145 has shown that, contrary to the prevailing opinion, creatine ingested, 

 especially after a period with food in which the protein content of the body 

 has been somewhat lowered, i. e., after a low protein diet, is not excreted 

 unchanged, nor indeed is it excreted in the form of creatinine. There is, 

 moreover, no corresponding increase in the total nitrogen elimination, and 

 hence it would appear that under these conditions the creatine is retained by 

 the body. On the other hand, his experiments show that when the body is 

 surcharged with protein, as after a high protein diet, the creatine ingested is 

 in large part excreted as such. These results are difficult to harmonize with 

 those obtained in the fasting experiments here reported unless some such 

 assumption as is suggested above is made. 



During a low protein diet the creatine of the muscles is apparently drawn 

 upon and whether it is excreted as creatine or as creatinine we as yet do not 

 know. Under such conditions, then, the ingestion of creatine supplies the 

 drafts upon the body creatine and there is no loss through the urine. It 

 would be interesting to see how soon the store of creatine in the body would 

 be replenished and the excess excreted in the urine with the subject remaining 

 on a low protein diet. 



145 Festschrift fur Olof Hammarsten (1906). 



