CHEMICAL BASIS OF THE ANIMAL BODY. 1247 



10. Creatine. C 4 H 9 N 3 O 2 . [NH : C<gf H >' CH ' COOH]. 



(Methyl-guanidinacetic acid.) 



By the union of ammonia with cyanamide a strongly alkaline 

 base, guanidine, is obtained: CN . NH 2 + NH 3 = NH . C (NH ) 

 (see below). When sarcosine is employed instead of ammonia 

 a similar reaction takes place, resulting in the formation of 

 creatine : 



CN . NH 2 + CH 2 . NH(CH 3 ) . COOH = NH : C (NH 2 ) . N(CH 3 ) . CH 2 . COOH. 



Since sarcosine is methyl-amidoacetic acid it is at once obvious 

 that creatine may be regarded as being methyl-guanidinacetic 

 acid. When cyanamide is treated with boiling baryta-water 

 it takes up a molecule of water and yields urea, CN . (NH 2 ) + 

 H 2 O = CO(NH 2 ) 2 , hence, as might be expected, creatine yields 

 by similar treatment sarcosine and urea. This is to the physi- 

 ologist the most important chemical property of creatine, bear- 

 ing as it does so closely upon one possible source and mode of 

 formation of urea in the body. 



FIG. 204. CREATING CRYSTALS. (Krukenberg after Ktihne.) 



Creatine 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. 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 creatine very readily loses a mole- 

 cule of water and thus becomes creatinine, and that the latter 

 with equal readiness takes up a molecule of water to form 

 creatine. Hence the creatine 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 



