55 



258. Schiff's tfest. Dissolve a little uric acid in a small 

 quantity of sodium carbonate. By means of a glass rod 

 place a drop of silver nitrate solution on filter paper and 

 then a drop of the uric acid solution so that the two drops 

 partially overlap. A dark brown or black spot of reducing 

 silver appears. 



259. Hippuric acid (CgHgNO,) occurs in large quantities 

 in the urine of the horse and many herbivora. It is also 

 found in man, from 0.5 to i gram being excreted daily. It 

 dissolves readily in hot alcohol but is sparingly soluble in 

 water. It is not pre.sent in the urine of carnivora. The 

 amount in man is increased by eating pears, apples with 

 their skins, cranberries and plums. It seems to be formed 

 chiefly from the husks or cuticular structures. Nothing is 

 known of its clinical significance. 



260. Evaporate some of the herbivorous urine (50 cc.) 

 with nitric acid (10 cc.) in a hood and heat the residue in a 

 dry test tube. If hippuric acid be present an odor like that 

 of oil of bitter almonds is plainly observable, due to the 

 formation of nitrobenzol. 



261. Kreatinin, (C^H,N30) is related to the kreatin of 

 mu.scles. Add a very dilute solution of .sodium nitro-prus- 

 side to some omnivorous urine, and very cautiously some 

 caustic soda ; a ruby red color develops. Boil, the color 

 fades. While boiling add a little strong acetic acid, the color 

 changes to blue. 



262. Ferments in urine. It is said that urine contains 

 pepsin. Some observers .state that it also contains trypsin 

 and a sugar-forming ferment, but the latter statement is 

 denied. 



The morning urine .should be selected. Place in it for 

 several hours a little well washed and boiled fibrin. The 

 latter absorbs the ferment, and on placing it in 0.2 9^ hydro- 

 chloric acid at 40° C. the fibrin is dissolved and peptones 

 formed. Test for the peptones by the biuret reaction. 



