562 



THE URINE. 



[CH. XXXVII. 



acids (malic, tartaric, &c.) in the food. They are, therefore, 

 found in the urine of herbivora and vegetarians, whose urine is 

 thus rendered alkaline. Urine containing carbonates becomes, 

 like saliva, cloudy on standing, the precipitate consisting of 

 calcium carbonate, and also phosphates. 



Phosphates. Two classes of phosphates occur in normal 

 urine : 



(1) Alkaline phosphates that is, phosphates of sodium 

 (abundant) and potassium (scanty). 



(2) Earthy phosphates that is, phosphates of calcium (abun- 

 dant) and magnesium (scanty). 



- 435- Urinary sediment of triple 

 phosphates (large prismatic crystals) 

 and urate of ammonium, from urine 

 which had undergone alkaline fer- 

 mentation. 



Fig. 436. Mucus deposited from urine. 



The composition of the phosphates in urine is liable to variation. 

 In acid urine the acidity is due to the acid salts. These are 

 chiefly 



Sodium dihydrogen phosphate, NaH 2 P0 4 , and calcium dihydrogen 

 phosphate, Ca(H 2 P0 4 ) 2 . 



In neutral urine, in addition, disodium hydrogen phosphate 

 (Na2HP0 4 ), calcium hydrogen phosphate, CaHP0 4 , and magnesium 

 hydrogen phosphate, MgHP0 4 , are found. In alkaline urine 

 there may be instead of, or in addition to the above, the normal 

 phosphates of sodium, calcium, and magnesium [Na 3 P0 4 ,Ca3(P0 4 )2, 

 Mg 3 (P0 4 ) 2 ]. 



The earthy phosphates are precipitated by rendering the urine 

 alkaline by ammonia. In decomposing urine, ammonia is formed 

 from the urea : this also precipitates the earthy phosphates. The 

 phosphates most frequently found in the white creamy precipitate 

 which occurs in decomposing urine are 



