Creatinine and Creatine. 387 



Folin's es method for determining creatinine was used in the experiments with 

 the fasting girl Flora Tosea. It is not stated definitely whether the urine was 

 heated with hydrochloric acid before making the colorimetric observations. 

 It is not, therefore, clear whether the amounts of creatinine include preformed 

 creatine (as creatinine). Urine was collected in three periods of the day, from 

 10 a. m. to 4 p. m., 4 p. m. to 10 p. m., and 10 p. m. to 10 a. m. The last food 

 was taken on the morning of June 10, 1905, and no more food was consumed 

 until June 25. During the fasting period the subject remained at rest, save 

 for 2 hours of gymnastic exercise on June 17. The quantity of creatinine in 

 the urine on the day preceding the fast was 1.087 grams. The excretion de- 

 creased regularly and rapidly to the eighth day. On the day when muscular 

 exercise was taken, the creatinine amounted to only 0.469 gram, while on the 

 following day it rose to 0.689 gram. During the three days before muscular 

 work was done a total of 1.662 grams was excreted; the total output for the 

 three following days was 2.006 grams. The excretion then decreased to about 

 0.5 gram daily, remaining fairly constant during the remainder of the fast. 



The new method of Folin for determining creatinine by means of the Jaffe 

 reaction was used in many of the experiments here reported. This reaction 

 is not given by creatine and hence it is necessary to heat the urine with hydro- 

 chloric acid to convert the creatine to creatinine. A determination of the 

 creatinine in the urine before and after heating with hydrochloric acid gives, 

 therefore, a measure of the amount of creatine (in terms of creatinine) which 

 is present in the urine. It has been found in a large number of experiments, 

 that the amount of preformed creatine in the urine is normally very small. 



In table 203 the results of the creatine and creatinine determinations are 

 given for the fasting experiments, for the two food experiments following 

 fasting, namely Nos. 74 and 76, and for the two nitrogen metabolism experi- 

 ments Nos. 1 and 2 made with S. A. B. In all experiments after No. 74, the 

 determinations were generally made of both preformed and total creatinine 

 and consequently in the last column of the table is recorded the weight of 

 creatine (expressed as creatinine) excreted. 



In experiments Nos. 73 and 74 the quantities of urine that could be spared 

 for samples to be sent to New Haven were small, and hence the results were not 

 as satisfactory as those made in our laboratory where analyses could be repeated 

 as desired, and where they could be made on the day immediately following 

 the collection of the sample. It is, therefore, more especially with the experi- 

 ments beginning with No. 75 that the results are of especial importance. 



The excretion of total creatinine, namely, preformed creatinine plus creat- 

 inine formed by heating the creatine of the urine with acid, remains singularly 

 constant on all days of the fast, even during the 7-day fast, experiment No. 75. 



63 Zeitschrift f. physiol. Chemie (1904), 41, p. 223. 



