THE ORGANIC CONSTITUENTS OF THE URINE. 245 



food, and in part to the wear and tear which constantly goes on in 

 the muscular structures of the body. The latter source, as com- 

 pared with the former, is normally, however, of secondary impor- 

 tance, as the greater amount of kreatin which originates in the 

 muscles is, in health at least, transformed into urea. We accord- 

 ingly find that the elimination of kreatin is much reduced when the 

 animal is placed on a diet of milk exclusively, while it is increased 

 if a liberal amount of meat is ingested, or kreatin is administered 

 as such. On the other hand, we observe that muscular exercise in 

 itself does not call forth an increased excretion, although this has 

 recently been denied. Under pathological conditions, however, in 

 which an increased destruction of the albuminous constituents of the 

 body occurs, abnormally large quantities may be found in the urine, 

 although the patient receives food which is free from kreatin. In 

 such cases we may assume that the muscles have lost to a greater or 

 less degree the power of transforming kreatin into urea. Kreatin 

 itself has thus far not been found in perfectly fresh urine, but is 

 formed from the kreatinin on the occurrence of bacterial decomposi- 

 tion. The transformation of kreatin into its anhydride supposedly 

 occurs in the kidneys, and we accordingly find that in extensive 

 disease of these organs the elimination of kreatinin is diminished. 



Of late, it has been claimed that the kreatinin which is found in 

 muscle-tissue is not identical with the urinary kreatinin, and it has 

 even been suggested that the source of the latter may have to be 

 sought in other organs of the body, and notably in the thyroid 

 gland, in which kreatinin has been found in considerable amount. 

 It is, of course, possible that the substance may be formed in other 

 organs as well, but the evidence is conclusive that the urinary form 

 is largely derived from muscle-tissue. But even supposing that 

 future researches should show that the two bodies are isomeric, but 

 not identical, we could even then imagine that both originate from 

 the same substance. 



The amount of kreatinin which is normally found in the urine of 

 man is approximately 1 gramme, but varies, of course, with the 

 character of the food. 



Properties. Kreatinin crystallizes in colorless, highly refractive 

 monoclinic prisms, and is quite soluble in hot and cold water, less 

 readily so in alcohol, and is insoluble in ether. In aqueous solution 

 it is gradually transformed into kreatin. The same transformation 

 results more rapidly when the substance is heated in alkaline solu- 

 tion. It combines with acids and various salts to form crystalline 

 compounds, some of which are characteristic. This is true especially 

 of the chlorozincate (C 4 H 7 N 3 O 2 ) 2 .ZnCl 2 which results when a con- 

 centrated alcoholic solution of kreatinin is treated with a solution 

 of zinc chloride, which should be as little acid as possible. The 

 crystalline form of this compound depends very much upon its 

 purity. As first obtained from the urine, it occurs in the form of 

 varicose conglomerations, which usually adhere firmly to the walls 



