URINE. 133 



in the urine of healthy individuals may hecome of importance 

 in judging of pathological states ; for in fevers and other dis- 

 eases the amount of ammonia in the urine increases conside- 

 rably. It is possible that, by analysing the urine, we may, in 

 the increasing or decreasing amount of ammonia, obtain a 

 measure for the alterations which take place in diseases. But 

 the salts of potash, which are rarely absent, as well as the am- 

 monia which is formed by the action of bichloride of platinum 

 upon the organic constituents of urine, render this reagent (the 

 bichloride of platinum) very unsafe for determining the increasing 

 or decreasing amount of ammonia in the urine during disease. 

 The magnesia salts would, perhaps, answer this purpose better ; 

 the determinative examinations made with salts of magnesia 

 are inferior to those made with bichloride of platinum, but they 

 are exact enough for the purpose of comparison.] 



17. Lime. There is no difficulty in proving the existence 

 of lime in the urine. On adding oxalate of ammonia to fresh 

 urine, a nebulous turbidity of oxalate of lime is formed. If 

 the urine is somewhat concentrated by evaporation, a precipi- 

 tate is obtained which appears under the microscope as an 

 amorphous mass. 



When urine is allowed to stand till ammonia is developed, 

 phosphate of lime and ammoniaco-magnesian phosphate are 

 precipitated. The phosphate of lime may be recognized under 

 the microscope as an amorphous mass : sometimes, but rarely, 

 it occurs in a crystalline form. Both varieties are exhibited 

 in fig. 26. 



18. Magnesia. The lime having been precipitated as an ox- 

 alate, and free ammonia added to the filtered urine, ammoniaco- 

 magnesian phosphate will then be deposited. We have already 

 observed that this salt becomes spontaneously formed, if urine 

 is allowed to stand for some time, in consequence of the deve- 

 lopment of ammonia. A thin film may then be seen on the 

 surface, in which we may detect minute crystals, even with the 

 naked eye. The inner surface of the vessel is also covered with 

 a crop of similar crystals. Under the microscope the ammo- 

 niaco-magnesian phosphate may be recognized by the peculiar 

 crystalline form represented in fig. 27. 



