URINARY DEPOSITS. 125 



It is ( Treat the original ) No odour = Uric Acid. 

 obtained j powder with potash. j Odour of HN 3 = Ammonium Urate. 



The residue is not coloured, but becomes yellowish- ) _ Y .-, . 

 red on adding caustic potash . . . . \ ~ 



The residue is not coloured either by KHO or ) 



NH 4 HO ; the original substance is soluble in f 



ammonia, and on evaporation yields hexagonal f 

 crystals ........) 



Cystin. 



On heating, it gives an odour of burned feathers ; J 



the substance is soluble in KHO, and is preci- > = Proteid. 

 pitated therefrom by excess of HN0 3 . . ) 



7. B. Incombustible. 



(i. ) Urates (Na, Oa, Mg), are rarely met with as the sole con- 

 stituent. They give the murexide test. 



(ii.) Oxalate of Lime or Mulberry Calculi, so called because 

 their surface is usually tuberculated or warty ; they are hard, 

 dark brown, or black. These calculi, from their shape, cause 

 great irritation of the urinary mucous membrane. When in the 

 form of gravel, the concretions are usually smooth, variable in 

 size, pale grey in colour. Layers of oxalate of lime frequently 

 alternate with uric acid. When heated it blackens, but does not 

 fuse, and then becomes white, being converted into the carbonate 

 and oxide. The white mass is alkaline to test-paper, and when 

 treated with HOI, it effervesces (C(X). Oxalate of lime is not 

 dissolved by acetic acid. 



(iii.) Carbonate of Lime. Rare in man; when met with 

 they usually occur in large numbers. Dissolve with effervescence 

 in HC1. Sometimes crystals occur as a deposit. They are 

 common in the horse's urine. 



(iv.) Basic Phosphate of Lime Calculi are very rare, and are 

 white and chalky. 



(v.) Mixed Phosphates (Fusible Calculus) consist of triple- 

 phosphate and basic phosphate of lime. They indicate that the 

 urine has been ammoniacal for some time, owing to decomposi- 

 tion of the urea. They are usually of considerable size, and 

 whitish ; the consistence varies. When triple-phosphate is most 

 abundant, they are soft and porous, but when the phosphate of 

 lime is in excess, they are harder. A whitish deposit of phos- 



