CHAPTER V. 



CREATINE AND CREATININE, GLYCOCYAM1NE AND GUAN1DINES. 



A. Creatine and Creatinine. 



Creatine was described and named as long ago as 1835, by Chevreul 

 [1835], m a report to the French Academy of Sciences on commercial 

 meat extracts. Chevreul did not analyse the substance, but noticed 

 its resemblance to asparagine. Berzelius later failed to prepare 

 creatine, but Wohler succeeded, and when Schlossberger [1844] ob- 

 tained the same substance from the muscles of an alligator, its im- 

 portance as a general constituent of muscle was recognised. 



Our detailed knowledge of creatine dates from Liebig's classical in- 

 vestigation of the constituents of muscle juice [1847]. Liebig pre- 

 pared creatine from the flesh of various animals, analysed it and con- 

 verted it into its anhydride which he named creatinine and found 

 to be identical with a substance isolated three years previously from 

 urine by Pettenk'ofer [1844]. By boiling creatme with baryta, Liebig 

 further obtained a new substance, sarcosine. Dessaignes [1854, 1855] 

 showed that creatine is oxidised by mercuric oxide to methyl- 

 guanidine (" methyl-uramine "). Sarcosine was synthesised by Vol- 

 hard, who obtained creatine from it [1868], 



Our physiological knowledge of creatine and creatinine did not 

 advance so rapidly as the chemical, largely perhaps owing to the want 

 of a convenient and accurate method of estimation. Such a method 

 was, however, supplied by Folin in 1904, and this, together with his 

 theory of metabolism, has led during recent years to many investiga- 

 tions on the physiology of creatine and creatinine. 



Creatine was synthesised by Volhard [1868] by the action of 

 cyanamide on sarcosine in alcoholic solution at 100. 



/CH, 

 CH,.NH.CH, + CN.NH, CHj.N/ 



= ioOH 



Horbaczewski [1885] also obtained it by heating sarcosine with 

 guanidine carbonate to 140-160. The necessary sarcosine may be 

 obtained by the hydrolysis of caffeine, but neither of these syntheses is 

 so convenient as the preparation from natural sources. 



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