Uric Acid. 395 



considered. As was pointed out by Jaffe/ acetone gives the same color with 

 sodium picrate that creatinine produces. Folin 71 found that acet-acetic acid, 

 acet-acetic ether, and hydrogen sulphide also give the reaction, but, as he points 

 out, these constituents are all pathological and can easily be removed from 

 urine. With the urine from fasting men, the researches of Brugsch (12), 

 especially, have shown the presence of (3 oxybutyric acid as a constant constit- 

 uent as well as amino acids and acetone. Kuelz " showed that even after 3 or 

 4 days of fasting in the case of insane patients, (3 oxybutyric acid was present. 

 The influence of these acids on the Jaffe reaction has not to our knowledge been 

 studied. Since unquestionably acetone 73 is formed in the urine of fasting man, 

 it is at least possible that constituents other than creatinine may produce the 

 color with sodium picrate. 



No precautions were employed to remove these abnormal constituents of the 

 urine, but during the heating with hydrochloric acid the acetone would in 

 large part be expelled. 



It is possible to conceive of an increased production of compounds giving 

 a color with sodium picrate as the fast progresses, and thus, in part at least, 

 account for the apparently constant elimination of total creatinine. On the 

 other hand, it is hardly probable that the production of other color-producing 

 materials should proceed at such a rate as to exactly compensate for any 

 possible falling off in the production of creatinine, and hence while the results 

 must be accepted with some reserve, it would appear that during fasting, the 

 output of total creatinine remains constant, while the relative proportion 

 between preformed creatinine and creatine indicates a constant change, the 

 proportion of creatine increasing as the fast progresses. 



Since this report was written evidence regarding the presence of creatine in 

 pathological urine has been collected which would tend to sustain the alternate 

 explanation of the presence of creatine given in a subsequent section of this 

 report. (See p. 458.) 



URIC ACID. 



Unfortunately, the excretion of uric acid in fasting man has been only 

 imperfectly studied, and in the experiments here reported but few observations 

 were made. In some of the samples of the urine sent to New Haven for 

 determination of creatinine, Professor Mendel kindly made determinations of 

 the uric acid. It was found impracticable to carry out these determinations in 

 the subsequent experiments with the limited amount of urine at our disposal. 



T0 Zeit. f. physiol. Chemie (1886), 10, p. 399. 

 n Zeit. f. physiol. Chemie (1904), 41, p. 224. 

 73 Zeitschrift f. Biologie (1887), 23, p. 338. 



"E. & 0. Freund also report acetone and acet-acetic acid in Succi's urine during 

 the Vienna fast. 



