494 VICTOR C. MYERS 



have shown that the pig on a high protein diet from certain sources will 

 excrete creatin, while Benedict and Osterberg(a) have found that the phlor- 

 hizinized dog may eliminate very large amounts of creatin when fed on a 

 diet of thoroughly washed meat. 



Different hypotheses have been advanced to explain the excretion of 

 creatin in children, such as under carbohydrate feeding, high protein 

 feeding and acidosis, but the experimental evidence advanced in their 

 support is not entirely convincing, although all these factors undoubtedly 

 exert an influence under certain circumstances. It is now well known 

 that the administration of carbohydrate in starvation causes a disappear- 

 ance of the creatinuria. Denis and Kramer believe that the creatinuria 

 in normal children is due to the relatively high protein intake which is 

 the rule with practically all children, also that creatinuria may be pro- 

 duced in women by very high protein diets. In this view they are opposed 

 by Rose, Dimmitt and Bartlett. Denis and Kramer further suggest that 

 the excretion of creatin in children may also be due to the low saturation 

 point of immature muscle owing 'to the low creatin content of the muscle 

 of children and the relatively low level of protein consumption at which 

 appreciable quantities of creatin appear in the urine. In support of this 

 argument Gamble and Goldschmidt(a) have observed a practically complete 

 elimination of ingested creatin in an infant on a high protein diet. 



Granting that creatinin does come from creatin, the natural question 

 is: What is the precursor of creatin ? For this we have as yet no definite 

 answer. On account of its guanidin group, arginin naturally suggests 

 itself. The very close chemical relationship between arginin and creatin 

 is apparent from the formula of arginin. 



- CH 2 - CH 2 -Clio - CH(NH 2 ) - COOH 



Arginin, or guanidin-amino-valerianic acid. 



If arginin is the source it is transformed only in small part to creatin, 

 since the amount of the daily creatinin excretion could account for only a 

 small part of the arginin normally metabolized. From the studies of 

 Kossel and Dakin it appears that the greater part of the arginin is 

 hydrolyzed to ornithin and urea by the enzyme arginase, but experimental 

 data to show that creatin is derived from arginin are inconclusive. That 

 creatin is not present in invertebrate muscle has long been known, although 

 the presence of arginin and likewise betain has been shown. The possi- 

 bility that betain, and also the closely related cholin, are the percursors 



