786 URINE. 



The simple uric-acid calculus leaves very little residue when burnt on 

 a platinum foil. It gives the murexid test, but there is no material 

 development of ammonia when acted on by caustic soda. 



Ammonium urate calculi occur as primary calculi in new-born or nurs- 

 ing infants, rarely in grown persons. They often occur as a secondary 

 formation. The primary stones are small, with a pale-yellow or dark- 

 yellowish surface. When moist they are almost like dough; in the 

 dry state they are earthy, easily crumbling into a pale powder. Thev 

 give the murexid test and develop much ammonia with caustic soda. 



Calcium-oxalate calculi are, next to uric-acid calculi, the most abundant. 

 They are either smooth and small (HEMP-SEED CALCULI) or larger, of the 

 size of a hen's egg, with rough, uneven surface, or their surface is cov- 

 ered with prongs (MULBERRY CALCULI). These calculi produce bleeding 

 easily, and therefore they often have a dark-brown surface due to decom- 

 posed blood-coloring matters. Among the calculi occurring in man 

 these are the hardest. They dissolve in hydrochloric acid without 

 developing gas, but are not soluble in acetic acid. After gently heating 

 the powder, it dissolves in acetic acid with frothing. With more intense 

 heat it becomes alkaline, due to the production of quicklime. 



Phosphate Calculi. These, which consist mainly of a mixture of the 

 normal phosphate of the alkaline earths with triple phosphate, may be 

 very large. They are as a rule of secondary formation and contain 

 besides these phosphates also some ammonium urate and calcium oxalate. 

 These calculi ordinarily consist of a mixture of three constituents 

 earthy phosphate, triple phosphate, and ammonium urate surrounding 

 a foreign body as a nucleus. Their color is variable white, dingy white, 

 pale yellow, sometimes violet or lilac-colored (from indigo red). The 

 surface is always rough. Calculi consisting of triple phosphate alone 

 are seldom found. They are ordinarily small, with granular or radiated 

 crystalline fracture. Stones of mono-acid calcium phosphate are also 

 seldom obtained. They are white and have beautiful crystalline texture. 

 The phosphatic calculi do not burn up, the powder dissolves in acid 

 without effervescence, and the solution gives the reactions for phos- 

 phoric acid and the alkaline earths. The triple-phosphate calculi generate 

 ammonia on the addition of an alkali. 



Calcium-carbonate calculi occur chiefly in herbivora. They are seldom found 

 in man. They have mostly chalky properties, and are ordinarily white. They 

 are completely or in great part dissolved by acids with effervescence. 



Cystine calculi occur but seldom. They are of primary formation, of various 

 sizes, sometimes as large as a hen's egg. They have a smooth or rough surface, 

 are white or pale yellow, and have a crystalline fracture. They are not very 

 hard and are consumed almost entirely on the platinum foil burning with a bluish 

 flame. They give the above-mentioned reactions for cystine. 



Xanthine calculi are very rarely found. They are also of primary formation. 

 They vary from the size of a pea to that of a hen's egg. They are whitish, yel- 



