ELEMENTS OF COMPOSITION. 



45 



Kreatin is found (but only in small amount) in the juices of the muscles 

 of man, and the vertebrates generally ; also in the fluid saturating the 

 brain (in the dog, according to Staedeler, together with urea), in the 

 testes (?), and in the blood ( Verdeil and Marcet Voigt). In the urine it 

 is said by Heinz not to exist primarily, but to be formed secondarily 

 from kreatinin. 



Kreatin may be looked upon us a decomposition product of muscle and 

 the substance of the brain, leaving the body through the kidneys. Per- 

 haps the greater part of the kreatin Avhich is formed in the body under- 

 goes immediate decomposition, and is one of the sources of urea. This 

 seems probable when we remember the mode in which it is split up by 

 boiling with baryta water. 



Kreatinin, C 4 H 7 N 3 . 



This substance, nearly allied to kreatin, crystallizes in colourless oblique 

 rhombic pillars belonging to the monoklinic system (fig. 27). In contra- 

 distinction to the compound last men- 

 tioned, kreatinin possesses strongly basic 

 properties, and is readily soluble in water. 

 With acids it combines to form crystal- 

 line and usually soluble salts. 



Kreatinin may be obtained by treat- 

 ing kreatin with acids. A watery solu- 

 tion of kreatinin, on the contrary, be- 

 comes again transformed into kreatin. 



Boiled with baryta water, it splits up 

 into ammonia and methylhydantoin, 

 C 4 H 6 N 2 2 . It is now looked upon as 

 glykolylmethylguanidin. 



Kreatinin is.a constituent of the juices 

 of muscle, and appears in the urine; 

 here it is present in large quantities, 

 and becomes transformed, as already 

 remarked, into kreatin. Verdeil and Marcet state that they have found 

 it, like the latter, in the blood: 



31. 

 Leucin, C 8 H n (NH 2 )O 2 . 



Leucin, or amidocapronic acid, is produced by the artificial decomposi- 

 tion of the protein compounds, glutin-yielding matters and elastin, by 

 means of acids or alkalies. It is, likewise, met with as a product of the 

 putrefaction of albuminous substances, like tyrosin, to be alluded to pre- 

 sently, and as such it was discovered many years ago by Proust. 



Through the investigations of Frerichs and Staedeler, who showed it to 

 be a physiological decomposition product widely distributed throughout 

 the body, it has become of much interest. Contributions on the same 

 point have also been made by Clo'etta and Virchow. Many of these 

 statements, moreover, are confirmed by Gorup-Besanez and Radziejewsky, 



Leucin is met with as a crystalline substance, partly (but only rarely 

 and when very pure) in delicate kliriorhombic plates, partly in spheroidal 

 lumps possessing a very characteristic appearance. They are either small 

 globules (a), or hemispheres (b b), or aggregations of rounded masses (c c d), 



Fig. 27. Crystals of kreatiniu. 



