CH. XXXVII.] URINARY DEPOSITS 569 



only in acid urine, and they may form concretions or calculi. 

 Cystinuria (cystin in the urine) is hereditary. 



Deposit of Phosphates. These occur in alkaline urine. The 

 urine may be alkaline when passed, due to fermentative changes 

 occurring in the bladder. All urine, however, if exposed to the air 

 (unless the air is perfectly pure, as on the top of a snow mountain), 

 will in time become alkaline, owing to the growth of the micrococcus 

 urece. This forms ammonium Carbonate from the urea. 



CON 2 H 4 + 2H 2 = (NH 4 ) 2 C0 3 . 



[Urea.] [Water.] [Ammonium 



carbonate.] 



The ammonia renders the urine alkaline and precipitates the 

 earthy phosphates. The chief forms of phosphates that occur in 

 urinary deposits are 



(1) Calcium phosphate, Ca 3 (P0 4 ) 2 ; amorphous. 



(2) Triple or arnmonio-magnesium phosphate, MgNH 4 P0 4 ; coffin- 

 lids and feathery stars (fig. 431). 



(3) Crystalline phosphate of calcium, CaHP0 4 , in rosettes of 

 prisms, in spherules, or in dumb-bells. 



(4) Magnesium phosphate, Mg 3 (P0 4 ) 2 + 22H 2 0, occurs occasion- 

 ally, and crystallises in long plates. 



All these phosphates are dissolved by acids, such as acetic acid, 

 without effervescence. 



A solution of ammonium carbonate (1 in 5) eats magnesium 

 phosphate away at the edges ; it has no effect on the triple phosphate. 

 A phosphate of calcium (CaHP0 4 + 2H 2 0) may occasionally be 

 deposited in acid urine. Pus in urine is apt to be mistaken for 

 phosphates, but can be distinguished by the microscope. 



Deposit of calcium carbonate, CaC0 3 , appears but rarely as 

 whitish balls or biscuit-shaped bodies. It is commoner in the urine 

 of herbivora. It dissolves in acetic or hydrochloric acid, with 

 effervescence. 



The following is a summary of the chemical sediments that may 

 occur in urine : 



CHEMICAL SEDIMENTS IN URINE. 



IK ACID URINE. 



Uric Acid. Whetstone, dumb-bell, 

 or sheaf-like aggregations of crystals 



IN ALKALINE URINE. 



Phosphates. Calcium phosphate, 

 Ca.j(PO 4 ) 2 . Amorphous. 



deeply tinged by pigment. Triple phosphate, 



Urates. Generally amorphous. The j MgNH 1 PO 4 + 6H 2 O. Coffin-lids or 



acid urate of sodium and of ammonium | feathery stars, 



may sometimes occur in star-shaped i Calcium hydrogen phosphate, 

 clusters of needles or spheroidal clumps CaHPO 4 . Rosettes, spherules, ordumb- 



with projecting spines. Tinged brick- 

 red. Soluble on warming. 



Calcium Oxalate. Octahedra, so- 



bells. 



Magnesium phosphate, 

 Mg 3 (PO 4 ) 2 + 22H 2 O. Long plates. 



