CHEMICAL COMPOSITION OF THE HUMAN BODY 49 



If to an alkaline solution of kreatinin a few drops of 

 sodium nitroprusside are added, a red color is produced 

 which soon disappears (Weyl's kreatinin test). This color 

 is not brought back by the addition of acetic acid, like that 

 of aceton. Kreatinin unites with zinc chloride, forming 

 kreatinin zinc chloride, a slightly soluble, double salt which 

 readily crystallizes. 



Kreatin is found in the blood and in many organs, 

 especially in the muscles. It is regarded as a precursor of 

 urea. Kreatinin is a constituent of urine. 



It is a question whether the kreatinin of urine is formed 

 from the kreatin of the muscles. The amount of kreatin in 

 the muscles is said to be increased by muscle activity, not 

 so the kreatinin of the urine. On the other hand, it has 

 been observed that kreatin fed to animals increases the 

 amount of kreatinin in the urine correspondingly. 



Carnine, C,H 8 N 4 O 3 , is also a constituent of muscles. By oxida- 

 tion with nitric acid it is changed to hypoxanthin. 



Cystin, a nitrogenous body found in urine during pathological 

 conditions (increased putrefaction in the intestine, diseases of 

 intestine), is the disulphide of amido-ethylidene lactic acid: 



CH S \ /CH 3 



COOH/\~ / \COOH. 



NH 2 NH^ 



Cystin is of interest because in it sulphur is excreted from the 

 body in unoxidized form. 



7. Bile acids are the union of a nitrogenous with a non- 

 nitrogenous acid. The nitrogenous part is an amido-acid 

 (glycocoll or taurin) ; the non-nitrogenous part is a cholalic 

 acid (or fellic acid). 



The bile acids are soluble in water and alcohol but in- 

 soluble in ether. They are precipitated in crystalline form 

 from the alcoholic solution by ether. They give a cherry- 

 red color with furfurol, or cane-sugar, and concentrated 

 sulphuric acid (Pettenkofer's test). They are monobasic 

 acids which form salts with alkalies. These salts are dextro- 

 rotatory. 



