21(J 



A Manual of Veterinary Physiology. 



half its bulk, and then adding the acid. The crystals should 

 be examined microscopically to prove their nature, as hip- 

 puric acid may be thrown down (Fig. 12). Should albumin 

 be present in the urine, it must be removed before carrying 

 out the urea test. 



Hippuric Acid is precipitated by evaporating the urine to 

 half its bulk with milk of lime, and adding HC1 in excess ; 

 either at once or in the course of a few hours dark sea- weed- 

 like masses of impure crystals are obtained (Figs. 13 and 14). 



Benzoic Acid is obtained by the same method as hippuric. 

 The deposit is much more granular and occurs immediately 

 on the addition of the acid ; but the microscope should be 



Fk;. 15.— Ckysta 



At in. 



used to determine between them, hippuric acid being in 

 long needles, benzoic in irregular leaf-like plates (Fig. L5). 



Uric Acid, if present (abnormal), is precipitated by 

 evaporating the urine to small bulk and adding 11(1. 

 The crystals may be identified by the microscope (Fig. L6), 

 or by evaporating them to dryness by means of gentle heat 

 with nitric acid on a white surface, and touching them with 

 dilute ammonia, a beautiful purplish-red colour is developed. 

 This is known as the nuirexido test. 



Indigo is readily precipitated in a while basin by the IK'l 

 method. On standing a few hours the vessel has well- 

 marked films of blue on it. 



