298 THE URINE. 



Fats, Cholesterin, and Lecithins. 



Fats. Traces of fat may be observed in the urine under normal 

 conditions when excessive amounts have been ingested. During 

 pregnancy also a lipuria has been noted, and is probably associated 

 with the development of the function of lactation. Otherwise the 

 condition is essentially a pathological phenomenon, and is notably 

 observed in acute yellow atrophy, in phosphorus poisoning, follow- 

 ing fracture of the long bones, etc. The largest amounts, however, 

 are found in cases of so-called chyluria. Owing to the existence of 

 the fats in fine emulsions, such urines may resemble milk in their 

 general appearance, and on standing a layer of "cream" forms at 

 the top. 



To establish the presence of fats, the surface layer of the urine is 

 extracted with ether, the ether is evaporated, and the residue brought 

 in contact with a piece of paper, when characteristic stains result. 



Cholesterin. Cholesterin is very rarely found in the urine, and 

 has thus far been encountered only under pathological conditions. 

 It probably always occurs in crystalline form, and is thus readily 

 recognized. If any doubt exists, the substance in question is 

 examined as has been described (page 163). 



Lecithins. Lecithins as such have been observed in the urine 

 only in chyluria, where they are commonly present in association 

 with cholesterin and fat. One of the derivatives of lecithin, how- 

 ever, is found also in the urine under normal conditions, though 

 in very small amounts. This is glycerin-phosphoric acid. It is no 

 doubt referable to decomposition of the lecithins of the food in the 

 intestinal canal, but may at times also be derived from the lecithins 

 of the tissues. To demonstrate its presence, several liters of urine 

 are freed from the common phosphates by rendering the urine 

 alkaline with barium hydrate and precipitating the heated mixture 

 with barium chloride. The excess of barium is removed with 

 carbonic acid and the filtrate evaporated to a syrup. This is ex- 

 tracted with absolute alcohol, when the remaining material is dis- 

 solved in a little water and boiled with hydrochloric acid. The 

 glycerin-phosphoric acid is thus decomposed, with the liberation of 

 glycerin and phosphoric acid. On evaporating to dryness, the 

 residue is extracted with water, and the presence of phosphoric 

 acid demonstrated in the aqueous solution by the usual tests. 



Ferments. 



Every urine contains ferments which are thought to be identical 

 with the pepsin, ptyalin, and chymosin of the digestive fluids. It 

 can be shown, as a matter of fact, that substances are present 

 which are capable of digesting fibrin in acid solution, of inverting 

 starch to maltose, and of coagulating milk. There is no proof, 

 however, that these bodies are derived from the digestive glands, 

 as Neumeister and others claim. 



