CH. XII.] UNORGANISED SEDIMENTS. 319 



L. Urinary Sediments. 



For the proper examination of these substances a 

 hand centrifuge is desirable. The sediment obtained 

 should be examined microscopically, and chemically if 

 necessary. 



The sediments obtained are either organised or un- 

 organised. Organised sediments consist of casts of the 

 renal tubules, epithelial cells from different parts of the 

 urinary tract, pus, blood cells, spermatozoa, parasites, etc. 

 It is not thought advantageous to describe them in this 

 book. 



Unorganised sediments vary with the reaction of the 

 urine. The more common varieties are given below. 



In acid urine. 



Uric acid : light yellow to dark reddish-brown in 

 colour. Crystalline form very varied : rhombic prisms, 

 wedges, rosettes, dumb-bells, whetstones, butchers' trays, 

 etc. Soluble in sodium hydroxide and reprecipitated by 

 hydrochloric acid. 



Urates : pinkish, soluble on warming, sometimes 

 amorphous, sometimes crystalline, as " thorn-apples," fan- 

 shaped clusters of prismatic needles. 



Calcium oxalate : octahedra, with an envelope-like 

 appearance (squares crossed by two diagonals) ; also in 

 dumb-bells. Insoluble in acetic acid, easily soluble in 

 hydrochloric acid. 



Calcium hydrogen phosphates (stellar phosphates) : in 

 rosettes of prisms and in dumb-bells. Rather rare. 



Cystine : colourless hexagonal plates, soluble in 

 ammonia, insoluble in acetic acid. Very rare. 



