124 CREATIN AND CREAT1NIN 



into the other by the simplest sort of chemical interference 

 (boiling with acid) are bound to bear a direct physiological 

 relation to each other. To-day such a relation may be 

 looked upon as definitely proved from the works of Pekel- 

 haring and his school ; and we are justified in assuming that 

 the urinary creatinin owes its origin to anhydration of the 

 creatin (primarily appearing in the tissue protoplasm of the 

 body or introduced with meat food). 6 This anhydration is 

 not necessarily always a complete one, as greater or smaller 

 amounts of creatin usually coexist with creatinin in the 

 urine. For this reason in biological studies it is never re- 

 garded as sufficient to make an estimation of creatinin alone > 

 but to deal with the total amount of the two substances. In 

 the urine of birds the creatinin is of decidedly less impor- 

 tance than creatin. 7 



Creatase and Creatinase. Added difficulty in the study 

 of the problem arises from the fact that along with the 

 change of creatin into creatinin (apparently from the influ- 

 ence of anhydrating ferments) there also occurs a decompo- 

 sition of both substances in the tissues. Gottlieb and 

 Stangas singer, 8 who are responsible for this important 

 observation, ascribe it to the influence of special ferments 

 (creatase and creatinase). Arginase is not involved in the 

 process. 9 The chemical course of this process of decomposi- 

 tion, which is also to be met in excised living organs, is 

 unknown. The cyclically formed creatinin is apparently 

 affected with more difficulty than the creatin. Creatin 

 which has been introduced parenterally into the circula- 

 tion of mammals is partly decomposed in the body ac- 



Cf. E. P. Cathcart (Glasgow), Jour, of Physiol., 39, 320, 1909; D. Noel 

 Paton, ibid., 39, 485, 1910. 



1 D. Noel Paton, 1. c. 



8 R. Gottlieb and R. Stangassinger, Zeitschr. f. physiol. Chem., 52, 1 1907; 

 55, 295, 322, 1908. 



H. D. Dakin (C. A. Herter's Lab., New York), Jour, of Biol. Chem., 3, 

 435, 1907. 



