CHEMICAL BASIS OF THK ANIMAL BODY. 145 



tions of kreatinin on the other hand are striking (see below), and 

 hence kivutiu may be identified with most certainty by conversion 

 into kreatinin, and the determination of the presence of the latter 

 substance. The conversion is readily effected by boiling with di- 

 lute mineral acids, during which process kreatin loses one molecule 

 of water : C 4 H 9 N,O 8 = CH 7 N 8 O + H 2 0. 



M- -1111011 has already been made of the possible and very 

 probable genetic relationship of urea to muscle-kreatin (see 

 484). This is a question to which brief reference will again 

 be made under urea, 



r /NH - CO -i 



G. Kreatinin. C 4 H 7 N,0. NH : C 



L \N(CH,).CH 2 J 



Kreatinin as already stated is simply a 'dehydrated form of 

 kivatin. It occurs normally as a constant constituent of urine, 

 varying however in amount from 0'5 to 4*9 grm. per diem accord- 

 ing to the amount of proteid food (meat) eaten. 1 It is not a nor- 

 mal constituent of mammalian muscle but is found in the muscles 

 of some fishes, 2 and has been obtained from sweat. 8 It crystal- 

 lises in colourless prisms or tables according to the conditions 

 under which the separation takes place and the mode of pre- 

 paration, and frequently, owing to imperfect development, the 

 < nstals assume a very characteristic 'whetstone' form. 



Fio. 10. KREATINIS CRYSTALS. (Krukenberg after Kiihne.) 



Ki'-atinin is readily soluble in cold water (1 in 11*5), also in 

 alcohol, but is scarcely soluble in ether. The aqueous solutions 

 an- usually alkaline, but some observers regard the alkalinity as 

 <luc to impurities. 4 It acts as a powerful base, forming compounds 



1 Volt, /-. ,-it. (sub kreatin). 



J Kriik.-nlMTj.'. f'nt.ra. iihi/sioi. fn*t. Hcidclb. Bd. iv. Hf. 1. 0881), 8. 33. 

 * Onpranii-a, /Ml. It. Arr-nl. m.<L /.'..ma, Ann. VIM. (1882), No. 6. 

 Salkowski, Zt.f.phytiol. Chem. Bde. iv. (1880), S. 133; XH. (1888), S. 211. 



10 



