MICROSCOPICAL DIAGNOSIS. 



scope will show, besides the crystals of uric acid, the cube crys- 

 tals of the chloride of. .sodium and potassium. If the deposit 

 be urate of ammonia then the leafy crystals of chloride of 

 ammonium will be found. If the urate of ammonia deposit be 

 treated with nitric acid and then filtered, and the deposit al- 

 lowed to dry on the filter, and if to this dry deposit ammonia 

 be added a beautiful purple or violet-red color will be pro- 

 duced. This is known as the "murexide test." 



The Earthy Phosphates. The earthy phosphates are insol- 

 uble in water and alkaline solutions, but soluble in acids. The 

 more common forms are the triple phosphate and phosphate of 

 lime. The phosphates are deposited from the alkaline and neu- 

 tral urine, and sometimes from urine feebly acid. The most 

 common form of the crystals of the triple-phosphate is that of 

 a triangular prism with beveled edges. The terminal edges are 

 sometimes also beveled ; when this condition exists and when 

 the crystal is much reduced in length, it appears almost square 

 and closely resembles the octahedral crystal of oxalate of lime. 

 The crystals of ' the triple-phosphate are soluble in acetic acid, 

 but the octahedra of oxalate of lime are unaffected by it. The 

 earthy phosphates are insoluble in hot water, and are unaffected 

 by alkalies. When ammonia is added to the healthy urine the 

 crystals assume the stellate form, consisting of from four to 

 five or six feathery rays. Beautiful crystals of the triple-phos- 

 phate are not unfrequently found among the urates. If the 

 turbidity of the urine be due to the presence of the phos- 

 phates a few drops of any acid will clear the specimen up. 

 If the urine has been secreted recently, boiling will precipitate 

 the phosphates, and acids will again render the mixture clear. 

 If an excess of ammonia be added to the urine, agitated, and 

 then allowed to rest, a precipitate of the earthy phosphates will 

 be. found ; this precipitate can be redissolved by acids. 



Phosphate of Lime. Phosphate of lime is found in pale 

 urine having a faintly acid reaction, with a tendency to alka- 

 line fermentation. It is frequently associated with the oxalate 

 of lime. It crystallizes as small rods, either singly or in stel- 

 late groups, or arranged in the form of bundles or rosettes 

 It may be composed of needle-shaped crystals, crossing each 

 other at right angles and lying together. The deposit may be 



