144 



KREATIN. 



kreatin may be regarded as being methyl-guanidinacetic acid 1 . 

 When cyanamide is treated with boiling baryta water it takes up 

 a molecule of water and yields urea, ON . (NH 2 ) + H 2 = CO (NH 2 ) 2 , 

 hence as might be expected, kreatin yields by similar treatment 

 sarkosin and urea. This is to the physiologist the most important 

 chemical property of kreatin, bearing as it does so closely upon one 

 possible source and mode of formation of urea in the body. (See sub 

 urea.) 



Kreatin occurs as a constant and characteristic constituent of muscles 

 and their extracts to an amount which is variable but may be taken as 

 from 0*2 0'3 p. c. on the weight of the muscle 2 . It is also found in 

 nervous tissue and is said to occur in traces in several fluids of the body. 

 It must however be carefully borne in mind that kreatin very readily 

 loses a molecule of water and thus becomes kreatinin, and that the 

 latter with equal readiness takes up a molecule of water to form 

 kreatin. Hence the kreatin obtained during any analysis need not at 

 all necessarily imply its presence as such in the original tissue or fluid 

 unless due allowance has been made for the possible effect of the 

 methods employed upon the reciprocal conversions of kreatin and 

 kreatinin. This is the cause of the conflicting statements as to the 

 occurrence of kreatin in urine ; as a matter of fact this excretion 

 always contains kreatinin. It is on the whole most probable that 

 any kreatin which may be found in urine is due to the conversion of 

 kreatinin into kreatin during its extraction, since it has been shewn ; 



FIG. 9. KBEATIN CBYSTALS. (Krukenberg after Kiihne.) 



that the more rapidly the separation is effected, the less is the 

 quantity of kreatin obtained, and the greater the amount of kreatinin. 



1 Of. Horbaczewski, Wien. med. Jahrb. 1885, S. 459. 



2 Voit, Zt. f. BioL Bd. iv. (1868), S. 77. 



3 Dessaignes, Jn. de Pharm. et Chim. (3) T. xxxn. (1857), p. 41. 



