362 THE MUSCLE-TISSUE. 



results, possibly combines with lactic acid, and is then further trans- 

 formed into urea in the liver. 



While the kreatin, which is thus produced during the nitrogenous 

 metabolism of the muscle-tissue, is largely transformed into urea, it 

 is noteworthy that the substance, when ingested by the mouth, 

 reappears in the urine in practically the same amount. This ob- 

 servation is explained by the assumption that the kreatin in this 

 case does not pass through the muscles, and thus escapes decom- 

 position, and there can be no doubt that a certain fraction of the 

 kreatin which is eliminated in the urine is referable to this source. 



Properties. Kreatin crystallizes in rhombic prisms, with one 

 molecule of water, which escapes at 100 C. It is readily soluble 

 in warm water, less so in cold water, and is insoluble in alcohol and 

 ether. 



As has been indicated before, it can be formed synthetically from 

 cyanamide and methyl-glycocoll, according to the equation : 



/NH, 



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

 Cyanamide. Methyl-glycocoll. \N(CH 3 ).CH 2 .COOH 



Kreatin. 



On boiling its acidified aqueous solutions, the substance loses 

 water and is transformed into kreatinin, from which the kreatin is 

 again obtained by treating with dilute alkaline solutions. The 

 transformation of kreatinin into kreatin can indeed take place in the 

 aqueous solution directly, and may be hastened by the application 

 of heat. The relation between the two substances can thus be 

 illustrated by the equation : 



/NH 2 /NH 



NH=C< = NH=C< + H 2 



\N(CH 3 ).CH 2 .COOH \N T (CH 3 ).CH 2 .CO 



Kreatin. Kreatinin. 



The same relation thus existr between kreatin and kreatinin as 

 between glucocyamin and glucocyamidin, and, as a matter of fact, 

 both are methyl-substitution-products of the two latter, and are 

 accordingly also termed methyl-glucocyamin and methyl-glucocy- 

 amidin. 



/NH 2 /NH, 



NH=C< NH=C< 



\NH.CH 2 .COOH \N(OH 3 ).CH 2 .COOH 



Glucocyamin. Kreatin. 



/NH CO /NH^ 



NH=C< | NH=C/ 



\N T H. CH 2 . \N(CH,).CH 2 .CO 



Glucocyamidin. Kreatinin. 



Kreatinin crystallizes in prisms, without water of crystallization, 

 and is soluble in water and alcohol (see also pages 84 and 246). 



Isolation of Kreatin. To isolate kreatin from muscle-tissue, this 

 is finely hashed and repeatedly extracted with an equal weight of 

 water at a temperature of from 55 to 60 C. The extracts are 



