Physical Properties of the Urine. 197 



Indican (C^H^ NSO/) is formed from indol which passes suc- 

 cessively through the forms of iudoxyle aud indoxylid potassio- 

 sulphate. This is uormally preseut in the urine, the horse excret- 

 ing I to 2 grammes daily, the dog 0.15 gramme. It is present in 

 excess in intestinal indigestions, constituting indicanuria. It is 

 tested by adding a drop of muriatic acid and one of a solution of 

 chloride of lime to the urine, when it will show a blue ring, the 

 depth of which indicates the relative amount. 



Urea (CON^, HJ the principal waste product of nitrogenous 

 matter, is always present in considerable amount. The sound 

 horse may eliminate 100 to 200 grammes dail}^ the dog 5 to 180 

 grammes. It is present in excess in all fevers and inflammations 

 unless urination is suspended or impaired, in cryptogamic diuresis, 

 in mellituria, uraemia, nephritis and cystitis. Test : The addition 

 to a filtered solution of urine, freed from phosphates, of solution of 

 acid nitrate of mercury, precipitates it as nitrate of urea. A 

 simpler test is to add to a drop or two of urine on a gla.ss slide a 

 drop of nitric acid and heat gently. The nitrate of urea is pre- 

 cipitated ill the characteristic rhombic or hexagonal crystals as 

 seen under the micro.'^cope. Heat urea crystals in a test tube : 

 biuret is formed and ammonia escapes. Add a trace of a copper 

 sulphate .solution and a few drops of a 20 per cent, solution of 

 caustic potash : a ro.se-red color is produced — the biuret reaction. 



Uric Acid (C^H^N^Og). Traces only of this are found in the 

 normal herbivorous urine, yet it is more abundant when on a full 

 dry grain diet, on milk (suckling) or on animal food. The dog 

 kept on animal food has a large amount. 



Pathologically it is produced in the dog and even in the 

 horse in fever, overwork and starvation, the animal living on his 

 own tissues. Interference with oxidation in the lungs .seems to 

 produce it as an arrest in the transformation of albuminoids to 

 urea. The neutral urate of soda remains in solution : the acid 

 urate of soda is precipitated. Test: To the urine add one-fourth 

 its volume or muriatic acid and .set aside for 24 hours in a cool 

 place. On the bottom and sides of the glass and on the surface 

 of the liquid will be found the yellowish red acicular cry.stals of 

 uric acid. 



Hippuric Acid (CgHgNOg) is normally present in all urine, 

 but is especially abundant in that of herbivora. The horse elim- 



