94 THE AMINO ACIDS 



tion is analogous to that of the kreatinine. It repre- 

 sents products which in the main are independent of 

 the total amount of sulphur eliminated or of protein 

 catabolized. 



7. Ethereal Sulphates. The ethereal sulphates rep- 

 resent a form of sulphur metabolism which becomes 

 more prominent when the food contains little or no 

 protein. 



Folin concludes that neither the theory of Voit nor 

 that of Pfliiger can be correct for these theories do not 

 harmonize with the above laws governing the compo- 

 sition of the urine. With respect to his own views he 

 says: "We have seen (from the tables) that the com- 

 position of urine, representing 15 gm. of nitrogen, or 

 about 95 gm. of protein, differs very widely from the 

 composition of urine representing only 3 gm. or 4 

 gm. of nitrogen, and that there is a gradual and regu- 

 lar transition from the one to the other. To explain 

 such changes in the composition of the urine on the 

 basis of protein catabolism, we are forced, it seems 

 to me, to assume that catabolism is not all of one 

 kind. There must be at least two kinds. Moreover, 

 from the nature of the changes in the distribution of 

 the urinary constituents, it can be affirmed, I think, 

 that the two forms of protein catabolism are essentially 

 independent and quite different. One kind is extremely 

 variable in quantity, the other tends to remain constant. 

 The one kind yields chiefly urea and inorganic sul- 

 phates, no kreatinin, and probably no neutral sulphur. 

 The other, the constant catabolism, is largely repre- 



