Creatinine and Creatine. 389 



The same may be said regarding the excretion of creatine in experiment 

 No. 77. In the shorter experiments, the amount of total creatinine, in general, 

 remains fairly constant. The results for creatine show a greater amount on the 

 second day of the experiment than on the first day in five of the experiments, 

 while in Nbs. 82 and 89, there is but a small quantity of creatine excreted on 

 both days, the lesser amount being excreted on the second day. 



The interpretation of these results, according to Folin's theory of protein 

 metabolism, would indicate that the amount of tissue protein disintegrated 

 (endogenous protein katabolism), even during a prolonged fast, remains 

 constant from day to day. While on the one hand it might reasonably be 

 expected that the tissue protein would be more rapidly katabolized during 

 fasting, when the body has to subsist on its own material, than during the 

 ingestion of food, yet on the other hand it is not difficult to conceive that 

 during fasting the body has the power to protect its organized or tissue protein 

 more thoroughly than when well supplied with food. Hence the constancy in 

 the total creatinine elimination, viewed in the light of the Folin theory, 

 furnishes no evidence to show either an increased or diminished endogenous 

 protein katabolism during inanition. 



While with a normally fed individual creatine is wholly converted by the 

 body to creatinine before being excreted, apparently with the fasting individual 

 the body gradually loses this power of converting creatine to creatinine as the 

 fast progresses. 64 



The data thus far obtained are insufficient to show clearly the true significance 

 of this abnormality in the power of the body to convert creatine. Further 

 experiments are necessary to solve this specific problem. The fact, however, 

 that during prolonged fasting the body loses to a marked degree the power of 

 converting creatine to creatinine is suggestive in interpreting results of the 

 katabolism of tissue protein and also of the synthetic power of the body in 

 general. It is furthermore clear that while the majority of the short experi- 

 ments indicate a loss of power of conversion, experiments should be continued 

 for more than two days to throw definite light on this subject. 



In a recent series of experiments made by Folin, 85 he has advanced the 

 suggestion that creatine when ingested is a food serving a purpose different 

 from that of the ordinary amino acids. These experiments imply that when the 

 body is flooded with protein, as after a diet rich in nitrogenous material, the 

 ingestion of creatine is followed by its immediate excretion, while creatine 

 ingested after the supply of reserve protein has been depleted by a low protein 

 diet is wholly retained in the body. Neither the creatine, creatinine, nor, indeed, 

 the total nitrogen excretion are affected by the ingestion of creatine under these 

 conditions. 



84 For another possible explanation of the increase in creatine excretion see p. 458. 

 86 Festschrift fur Olof Hammersten, Upsala (1906). 



