PHOSPHATES OF LIME AND MAGNESIA. 55 



salt increases in the various bones, the others, except the phosphate 

 of magnesia, diminish in proportion, and vice versa the proportion 

 of the principles of mineral origin remaining constantly the same 

 at all periods of life, and both in the compact and the cancellated 

 tissue. The salt just excepted, however, increases or diminishes 

 with the increase or diminution of the phosphate of lime. (R.and V.) 



This salt is in a solid state in bone, teeth, nails, and hair. Though 

 insoluble in water, it is in a liquid state in the blood and all the 

 other animal fluids, whether in its free state or combined with albu- 

 minous matters. When free, it is in solution by the aid of the free 

 carbonic acid in the blood, of the bicarbonates, or by the chloride 

 of sodium. 



In bone it is combined with their peculiar organfc substance 

 (osteine), and doubtless with the other earthy 

 salts. It is also combined with albumen and Fi g- 5 - 



fibrine in the blood, as has been seen. In the 

 urine it is held in solution by the acid phos- 

 phate of lime and of soda, and the other salts 

 of these two bases ; also by the carbonic acid 

 in the urine. Its appearance as a urinary de- 

 posit is shown by Fig. 5. 



This principle gives to several tissues their 

 physical properties of resistance and solidity, Phosphate of nme in amor- 

 upon which their uses principally depend. ^Sfiig^ 

 This is most apparent in the osseous tissue. 

 Liebig also ascribes to it the insolubility of certain tissues, as the 

 muscular and the areolar. 



It is derived from milk and other animal, and still more from 

 vegetable, diet. The phosphate of lime of bones i. e. the basic 

 phosphate exists in nature. It is evacuated in the urine. That 

 in the feces is the overplus in the aliment which had not left the 

 alimentary canal by absorption. A part is, however, changed into 

 the acid phosphate of lime, and then aids in the decomposition of 

 the tissues. 



The acid phosphate or biphosphate of lime exists in urine (and in 

 gastric juice?), and is formed, probably, from the basic phosphate. 



11. The Phosphate of Magnesia. (MgOP0 3 .) 

 This is found in all the tissues and fluids in the bodies of the 

 mammiferaB, but in all cases in small quantity. It is more abundant 

 in muscle, however, than the phosphate of lime. 



