ioo THE CHEMISTR Y OF THE TISSUES AND ORGANS. 



FIG. 13. Creatine crystals. After Kiiline. 



creatine, creatinine, xanthine, hypoxanthine, carnine, carnic acid, uric 

 acid, urea, taurine, and inosinic acid. (&) Non-nitrogenous, namely, fats, 

 glycogen, inosite, dextrose, and lactic acids. 



Creatine and creatinine. Creatine can be crystallised out by 



evaporating aqueous extracts 

 of meat from which proteids 

 and salts have been previously 

 removed ; 011 heating it with 

 mineral acids it is converted 

 into creatinine. The relation- 

 ship of these two substances 

 is shown by the following 

 equation : 

 C 4 H 9 N A H 2 - C 4 H T N 3 



(creatine) (creatinine) 



According to Yoit, 1 the 

 quantity of creatine in the 

 voluntary muscles varies from 

 0-2 to 0-3 per cent. This 

 increases during starvation. 2 



Involuntary (cardiac and plain) contains less than voluntary muscle. 8 

 The compound with zinc chloride which creatinine forms (Fig. 15) has 



been generally used for isolating it from urine, and other places where it 



occurs. .My own experience with 



j$,'\ r^SBfc this method has shown that for 



quantitative purposes it is most 

 uncertain ; and this no doubt ac- 

 counts for the different results 

 obtained by different observers. 

 Thus Neubauer denies the exist- 

 ence of creatinine in muscle 

 altogether ; Voit, Sarokin, 4 and 

 Monari 5 say that it increases 

 during muscular activity, while 

 Nawrocki 6 states that it does 

 not. Much more certain results 

 are obtained by the use of G. S. 

 Johnson's method, in which he 

 precipitates the creatinine as a 

 compound of mercury. 7 This 

 method, which has received the 



FIG. 14. Creatinine crystals. After Kiihne. 



powerful recommendation of Hoppe-Seyler, 8 may be used to identify 

 creatinine when it is present in very small quantities, as in the blood. 9 

 The microscopic appearance of the precipitate is shown in Fig. 16. By 



1 ZUchr.f. BioL, Miinchen, Bd. iv. S. 77. 



2 Demant, Ztsclir. f. physiol. Chem., Strassbnrg, Bd. iii. S. 387. 



3 Voit, loc. cit. ; Lehmann, " Lehrbuch," Bd. iii. S. 73. 



4 Virchow's Archiv, Bd. xxvii. 5 Gazz. chim. ital., vol. xvii. p. 36'7. 



6 Centralbl.f. d. med. Wisscnsch., Berlin, 1865, S. 417. 



7 Proc. Roy. Soc. London, vol. xlii. p. 365 ; xlii. p. 493 ; 1. p. 28. Johnson 

 here points out that there are several isomeric varieties of creatinine, differing in reducing 

 power, etc. In his process he is careful to employ no heat; otherwise the creatinine is 

 transformed into a non-reducing variety, or even may be changed into creatine. 



"Handbuch. d. physiol. clieni. Analyse," 1893, 7th edition, S. 142. 

 9 Colls, Journ. Physiol. , Cambridge and London, 1896, vol. xx. p. 107. 



