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HANDBOOK OF PHYSIOLOGY. 



cipal earthy constituent of bone, and from the decomposition of the 

 osseous tissue the urine derives a large quantity of this salt. The de- 

 composition of other tissues also, but especially of the brain and nerve- 

 substance, 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. This quantity is, however, liable to con- 

 siderable variation. Any undue exercise of the brain, and all circum- 

 stances producing nervous exhaustion, increase it. The earthy phos- 

 phates are more abundant after meals, whether on animal or vegetable 

 food, and are diminished after long fasting. The alkaline phosphates 

 are increased after animal food, diminished after vegetable food. Exer- 

 cise increases the alkaline, but not the earthy phosphates. Phosphorus 

 uncombined with oxygen appears, like sulphur, to be excreted in the 

 urine. When the urine undergoes alkaline fermentation, phosphates are 

 deposited in the form of a urinary sediment, consisting chiefly of ammo- 



FIG. 257. 



FIG. 258. 



FIG. 257. Urinary sediment of triple phosphates (large prismatic crystals) and urate of am- 

 monium, from urine which had undergone alkaline fermentation. 

 FIG. 258. Crystals of Cystin. 



* 



nio-magnesium phosphates (triple phosphate) (Fig. 257). This com- 

 pound does not, as such, exist in healthy urine. The ammonia is chiefly 

 or wholly derived from the decomposition of urea. 



(c) The Chlorine of the urine occurs chiefly in combination with 

 sodium (next to urea,. sodium chloride is the most abundant solid con- 

 stituent of the urine), but slightly also with ammonium, and, perhaps, 

 potassium. As the chlorides exist largely in food, and in most of the 

 animal fluids, their occurrence in the urine is easily understood. 



(8) Occasional Constituents. Cystin (C 3 H 7 NSO a ) (Fig. 258) 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 (Fig. 259) as 



