380 THE MUSCLE-TISSUE. 



According to Folin kreatinin represents the most important nitrog- 

 enous end-product of the muscle katabolism and is not further 

 converted into urea. As I have shown at another place, the latter 

 is the essential end-product of the exogenous metabolism, while 

 kreatinin represents the same principle for the endogenous metabo- 

 lism. Folin has demonstrated conclusively that on a kreatin in-free 

 diet the daily kreatinin elimination is for any given person practi- 

 cally a constant quantity and independent of how much or how little 

 protein is contained in the food. (See also Urine.) 



How kreatin is transformed into kreatinin within the body is not 

 known. Folin has shown that this is artificially effected only with 

 difficulty and it is possible that in the living body it may be brought 

 about through a ferment. 



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 2 



CN.NH 2 -f CH 2 .NH(CH 3 ).COOH = NH : C< 



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



Kreatin. 



The relation existing between kreatin and kreatinin can be repre- 

 sented by the equation : 



/NH, / NH -^ 



NH : C< = NH : C< ^-^ -f H.O 



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



Kreatin. Kreatinin. 



The same relation thus existf 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. 



X2 X2 



NH : C/ NH : C< 



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



Glucocyamin. Kreatin. 



/NH CO /NH_ 



NH : C< | NH : C( 



\NH. CH 2 . \N(CH 3 ).CH 2 .CO 



Glucocyamidin. Kreatinin. 



Kreatinin crystallizes in prisms, without water of crystallization, 

 and is soluble in water and alcohol (see also pages 1 08 and 263). 



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 

 boiled so as to remove coagulable albumins. The filtrate is pre- 

 cipitated with subacetate of lead, care being taken to avoid an 



