OCCASIONAL CONSTITUENTS OF URINE 385 



The phosphates are taken largely in both vegetable and animal food. 

 Some are excreted at once; others only after being transformed and incor- 

 porated with the tissues. Calcium and magnesium phosphates form the 

 principal earthy constituents of bone, and from the decomposition of the 

 osseous tissue the urine derives a quantity of this salt. The decomposition of 

 other tissues also furnishes large supplies of phosphorus to the urine, which 

 phosphorus is supposed, like the sulphur, to be united with oxygen, and then 

 combined with bases. The quantity is, however, liable to considerable 

 variation. The earthy phosphates are more abundant after meals, whether 

 of animal or vegetable food, and are diminished after long fasting. The 

 alkaline phosphates are increased after animal food, diminished after vegetable 



FIG. 299. Crystals of Cysttn, FIG. 300. Crystals of Calcium Oxalate. 



food. Phosphorus uncombined with oxygen appears, like sulphur, to be ex- 

 creted in the urine. When the urine undergoes alkaline fermentation phos- 

 phates are deposited in the form of a urinary sediment, consisting chiefly of 

 ammonio-magnesium phosphates (triple phosphate), figure 298. 



The Chlorine of the urine occurs chiefly in combination with sodium. 

 Next to urea, sodium chloride is the most abundant solid constituent of the 

 urine. As the chlorides exist largely in food, and in most of the animal fluids, 

 their occurrence in the urine is easily understood. 



Occasional Constituents of Urine. Cystin, C 3 H 7 NSO 2 , figure 299, 

 is an occasional constituent of urine. It resembles taurin in containing a 

 large quantity of sulphur more than 25 per cent. It does not exist in 

 healthy urine. 



Another common morbid constituent of the urine is Oxalic acid, which is 

 frequently deposited in combination with calcium, figure 300, as a urinary 

 sediment. Like cystin, but much more commonly, it is the chief constituent 

 of certain calculi. 



Dextrose and albumin are sometimes present in pathological urine, and are 

 of particular interest from the clinical point of view. See the subject Gly- 

 cosuria, page 418. 

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