DISEASES OF THE URINARY SYSTEM. 263 



Albumen may also be tested for by nitric acid. This 

 test consists in pouring into a test-tube a small quantity of 

 strong nitric acid, and then pouring very slowly down the 

 side of the tube a little of the urine to be examined. If 

 albumen be present an opaque white cloud forms immediately 

 where the two fluids come into contact. 



A saturated solution of picric acid also precipitates 

 albumen, and picric acid tablets are now sold by chemists, 

 and aff'ord a ready method by which the presence of albumen 

 may be detected. 



Bile Acids and Bile Pigment. — Under the diseases of the 

 liver, we have already spoken of the occasional presence of 

 bile acid and pigment in the urine, and have given tests by 

 which their presence may be recognised. 



Grape Sugar. — Grape sugar is found in the urine in 

 diabetes mellitus, under which disease tests by which this 

 substance may be detected have been mentioned. 



The fermentation test may also be applied. If a little 

 yeast be added to urine containing sugar, after standing for 

 some time in a warm place, it will ferment, with the disen- 

 gagement of carbonic acid. 



Pus and Mucus. — Pus is sometimes found in the urine, 

 which is albuminous in proportion to the amount of pus 

 present. If examined microscopically, the sediment is seen 

 to contain pus-cells which are very similar to white blood- 

 cells. They are, however, lifeless, and have no amoeboid 

 movements, and are characterized by the presence of se\^eral 

 nuclei. 



Section I. 



DISEASES OF THE KIDNEYS. 



RENAL CONGESTION. — Etiology and Symptoms.— 

 Hypersemia, or congestion of the kidneys, may be active or 

 mechanical. It is not often met with in the horse. 



