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HANDBOOK OF PHYSIOLOGY. 



must be formed during the metabolism of nitrogenous foods; the 

 sulphur of which the acid is formed being probably derived from the 

 decomposing nitrogenous tissues, the other elements of which are re- 

 solved into urea and uric acid. It may be in part derived also from the 

 sulphur-holding taurin and cystin, which can be found in the liver, 

 lungs, and other parts of the body, but not generally in the excretions; 

 and which, therefore, must be broken up. The oxygen is supplied 

 through the lungs, and the heat generated during combination with the 

 sulphur is one of the subordinate means by which the animal tempera- 

 ture is maintained. 



Besides the sulphur in these salts, some also appears to be in the 

 urine uncombined with oxygen; for after all the sulphates have been 

 removed from urine, sulphuric acid may be formed by drying and burn- 



Fig. 303. Fig. 304. 



Fig. 303. Mucus deposited from urine. 



Fig. 304. Urinary sediment of triple phosphates (large ^prismatic crystals) and urate of ammo- 

 nium, from urine which had undergone alkaline fermentation. 



ing it with nitre. From three to five grains of sulphur are thus daily 

 excreted. The combination in which it exists is uncertain : possibly it 

 is in some compound analogous to cystin or cystic oxide. Sulphuric 

 acid also exists normally in the urine in combination with phenol 

 (C 6 H 6 0) as phenol-sulphuric acid or its corresponding salts, with 

 sodium, etc. 



(I) The phosphoric acid in the urine is combined partly with the 

 alkalies, partly with the alkaline earths about four or five times r.s 

 much with the former as with the latter. In blood, saliva, and other 

 alkaline fluids of the body, phosphates exist in. the form of alkaline, 

 neutral, or acid salts. In the urine they are acid salts, viz., the sodium, 

 ammonium, calcium, and magnesium phosphates, the excess of acid 

 being (Liebig) due- to the appropriation of the alkali with which the 

 phosphoric acid in the blood is combined, by the several new acids 

 which are formed or discharged at the kidneys, namely, the uric, hip- 

 puric, and sulphuric acids, all of which are neutralized with soda. 



