THE METABOLISM OF PROTEIN 661 



is creatine in other organs than the muscles, it seems probable that the 

 substance has really little to do with muscular contraction as such, but 

 rather is concerned in some way in the formative metabolism of the cell, 

 with its general growth or maintenance. Indeed, it is a question whether 

 creatine is an actual constituent of the living tissue. It may rather, as 

 has been suggested by Folin, be a postmortem product, represented dur- 

 ing life by creatinine. 



Creatine appears in the urine in phosphorus poisoning, in carcinoma of 

 the liver and during postpartum involution of the uterus. It is not de- 

 rived from the disappearing uterine muscle, however, for creatinuria also 

 occurs after cesarean section with removal of the uterus. Creatine 

 elimination is not an index of cellular destruction. Muscular fatigue also 

 leaves the creatine content of muscle unchanged. In late stages of 

 nephritis, creatinine accumulates in the blood and serves as an index of 

 the gravity of the condition (page 683). 



