430 PHYSIOLOGICAL CHEMISTRY. 



urates in that they dissolve without a residue in dilute acids and 

 do not give the murexid test. 



Ammonium-magnesium phosphate, TRIPLE PHOSPHATE, may 

 separate indeed from an amphoteric urine in the presence of a suf- 

 ficient amount of ammonium salts, but it is generally characteristic 

 of an ammoniacal urine from alkaline fermentation. The crystals 

 are so large that they may be seen with the unaided eye as colorless 

 glistening particles in the sediment, on the walls of the vessel, and 

 in the film on the surface of the urine. This salt forms large 

 prismatic crystals of the rhombical system which are easily soluble 

 in acetic acid. Amorphous magnesium triphosphate, Mg 3 (P0 4 ) 2 , 

 occurs with calcium triphosphate in urines rendered alkaline by 

 a fixed alkali. Crystalline magnesium phosphate, Mg 3 (P0 4 )a -f- 

 22H 2 0, has been observed in a few cases in human urine (also in 

 horse's urine) as strongly-refractive, long rhombical plates. 



Kyestein is the film which appears after a little while on the surface of the 

 urine. This coating, which was formerly considered as characteristic of urine 

 in pregnancy, contains various elements, such as fungus, vibriones, epithelium- 

 cells, etc. It often contains earthy phosphates and triple- phosphate crystals. 



As more rare sediments we find cystin, tyrosin, hippuric acid, xanthin, 

 hwmatoidin. In alkaline urines blue crystals of indigo may also occur, due to 

 a decomposition of indoxyl-glycuronic acid. 



Urinary Calculi. 



Besides certain pathological constituents of the urine, all those 

 urinary constituents which occur as sediments take part in the for- 

 mation of the urinary calculi. EBSTEIJT considers the essential 

 difference between an amorphous or crystalline sediment in the 

 urine on one side and urinary sand or large calculi on the other 

 to be the occurrence of an organic frame in the last. As the sedi- 

 ments which appear in normal acid urine, and in an alkaline urine 

 due to fermentation are different, so also are the urinary calculi 

 which appear under corresponding conditions. 



If the formation of a calculus and its further development takes 

 place in an undecomposed urine, it is called a PRIMARY formation. 

 If, on the contrary, the urine has undergone alkaline fermentation 

 and the ammonia formed thereby has given rise to a calculous for- 

 mation by precipitating ammonium urate, triple phosphate, and 

 earthy phosphates, then it is called a SECONDARY formation. Such 



