CREATIN AND CBEATIXIX 175 



is low in creatin (Pekelharing and Van Hoogenhuyze (a), 1909; Jansen 

 (b) ). Voluntary muscle has an affinity for creatin, for when it is injected 

 into rabbits the creatin content of their muscles is increased by 5 per cent 

 (Myers and Fine (e), 1913). 



The constancy of the creatin content of muscle of a given species of 

 animal under uniform conditions of diet was first pointed out bv Myers 

 and Fine (c) (1913). During starvation or carbohydrate abstinence the 

 creatin content of muscle at first increases and then progressively de- 

 creases with the length of the fast (Mendel and Rose (6), 1911). " The 

 muscle of rabbits that had fasted for 6 days contained 0.55 per cent 

 of creatin, while that obtained from rabbits that had been starved for 24 

 days contained 0,36 per cent (Myers and Fine (d) 1913). The decrease 

 in creatin is explained by the loss of this substance through the urine. 



Benedict and Osterberg maintained phlorhizinized dogs in approximate 

 nitrogen equilibrium by feeding creatin free protein. Under these con- 

 ditions the excretion of creatin continued unchanged, and in spite of the 

 relatively large quantity lost in the urine the muscle of these animals 

 actually contained more than that of normal dogs. The authors conclude 

 that the creatin excreted in the urine is not dependent on the amount of 

 body tissue destroyed, that it is not derived from muscle creatin, and 

 further that creatin is probably formed in large amounts and is normally 

 utilized or destroyed for the greater part. The creatinin- of ' the urine 

 can only account for a small part of the creatin that is normally katabol- 

 ized. Folin and Denis (h) (1914) found that when creatin was injected 

 into cats it was absorbed by the muscles to an extraordinary degree. They 

 believe that living muscle does not contain free creatin and that that found 

 on analysis is a post-mortem product. The vital combination must be a 

 very loose one to be sure. 



According to several authors creatin is not destroyed during aseptic 

 or antiseptic autolysis of muscle (Denis (e), 1916 ; Mellanby (a) ). Myers 

 and Fine (k) (1915) find that no destruction of creatin or creatinin occurs 

 when rabbit muscle is permitted to autolyze (under aseptic conditions) at 

 body temperature. On the other hand the work of Iloagland and McBrydc 

 seems to show that during aseptic autolysis of beef muscle creatin at first 

 increases and then decreases. 



Blood. Normal blood contains between 3.5 and 6 milligrams of 

 creatin per 100 c.c. (Folin and Wu). In nephritis as much as 31.7 nigs, 

 have been observed (Myers and Fine(</), 1915 ). Though the concentration 

 of creatin in the blood is higher than that of creatinin the former is usually 

 not excreted by the kidney while the latter is a normal constituent of the 

 urine. In other words the renal threshold for creatinin is lower than for 

 creatin. The concentration of creatin in the plasma is lower than in 

 whole blood (Hunter and Campbell (?>)). 



