56 IMMEDIATE PRINCIPLES OF THE TISSUES. 



It is found, in a crystallized form, in the pus of abscesses of dif- 

 ferent organs, in the serosity of ovarian and other cysts, in that of 

 the pus of the pleura and peritoneum, and on the surface of carious 

 and necrosed bones. Ovarian calculi are sometimes composed 

 mainly of it, and a small quantity, at least, exists in all urinary 

 calculi. 



In human bone it constitutes 1.16 per cent.; in that of the herbi- 

 vora it is more abundant (2.05 per cent, in the ox). In the varying 

 physiological and pathological conditions it increases or diminishes 

 with the phosphate of lime. Of enamel it constitutes 1.5 per cent. ; 

 of dentine, 1 per cent. ; of muscle, .023 per cent. Cartilage contains 

 a large amount even 6.9 per cent.; and blood, .137 per cent. Hu- 

 man milk contains .05 per cent. 



In bone, nails, and teeth it is probably in a solid state, and com- 

 bined (as is always the case) with the phosphate of lime. Though 

 slightly soluble, it is doubtless directly dissolved in water. In bone, 

 &c., these two salts, first united together, combine with the plasma 

 to form the organic principle, or osteine. 



It is obtained, in the organism, from vegetable food; carnivorous 

 animals deriving it from the bones of the herbivora. It is excreted 

 principally in the urine ; the feces also containing any amount not 

 absorbed from the food, as well as that contained in the intestinal 

 and pancreatic fluids. The formation in the organism of ammonia 

 causes a part of this salt to pass into the state of ammonio-magne- 

 sian phosphate as in the feces, in cases of typhus and dysentery. 

 The function of the phosphate of magnesia in aid of endosmosis, 

 and of assimilation and ^-assimilation, may be associated with that 

 of phosphate of lime. 



121 Ammonio-Magnesian Phosphate. (MgO.NHO^HO.PO,..) 

 This is formed, as just explained, in the feces in disease, and in 

 the urine after standing twenty-four hours or less ; and sometimes 

 when first excreted, if the latter is alkaline. It may form in any 

 alkaline fluid containing the phosphate of magnesia. It is found in 

 vesical calculi, gravel, and sand, and still oftener in renal calculi ; 

 and in intestinal, salivary, uterine, and biliary calculi. In all cal- 

 culi it is habitually united to the phosphate of lime. It exists in 

 the fluid form only in acid urine, being but slightly soluble in warm 

 water and in solutions of other salts. A prolonged use of phosphate 

 of magnesia (or mineral water containing it), has produced a vesical 

 calculus, and in one instance even in two weeks. 



