Creatine of Muscle Under Normal Conditions. i i 



In view of the lack of proof of the connection of creatine and 

 creatinine in metabolism, our original experiments were planned 

 in an endeavor to ascertain whether in a given animal, in this case 

 the rabbit, there was a constant relationship between the total 

 creatine of the body and the daily creatinine. This ratio was 

 ascertained in a series of one growing and ten adult rabbits. It 

 was not absolutely constant, and appeared to vary with the 

 weight of the animal, being 53.3 : I, in an animal of 1.39 kilos 

 and 44.7 : I where the weight was 2.13 kilos. For five animals of 

 nearly the same weight, 1. 9-2.1 kilos, comparatively constant 

 ratios, 44.7, 45-0, 44.4, 44.4, and 44.9 : I were obtained. 



In a further attempt to ascertain any relationship between 

 body creatine and urinary creatinine, the figures for the creatine 

 concentration of the body were arranged in order of the creatinine 

 coefficients. The first five adult animals with an average coeffi- 

 cient of 13.6 had an average body creatine concentration of .170 

 per cent., while the second five animals with an average coefficient 

 of 15.0 had a creatine concentration of .193 per cent. 



Our fasting experiments below indicate that the amount of 

 creatine remaining in the body after starvation bears a relation- 

 ship, not only to the amount of creatine lost in the urine during this 

 period, but also to the amount of the creatinine elimination. 



An interesting observation with regard to the creatinine, in the 

 series of eleven normal animals, is that the amount of its average 

 daily elimination followed that of the body weight in every case. 

 This is in accord with Folin's original statement that body weight 

 appears to be the most important factor in determining the amount 

 of its elimination. 



It is not supposed that these experiments offer any definite 

 proof of the origin of the urinary creatinine from muscle creatine 

 or some common precursor substance, but in view of the fact 

 that no data have been adduced to show such a relationship, these 

 experiments may be of value as advancing this hypothesis. 



