Phosphate of lime occurs in the organism in three forms, viz.: as the normal calcium phos phate, t'a,IPO,),, the monocal(-ic calcium phos also called acid phosphate, and the tlicaHe phosphate, The normal phosphate occurs in all the solids and fluids of the body, but is most abundant in the bones, in which it amounts to about 57 per cent.; and in the enamel of the teeth, in which it ranges from SO to 90 per cent. It may at first sight ap pear inexplicable how a salt so perfectly insolu ble in water as normal phosphate of linw can be held in solution in the animal fluids. In some fluids. as the blood. it is probably, in part, at least, combined with albumen, with wine]] it forms a solulde compound; while in other fluids, as the urine, it is held in solution by a free acid or by certain salts (as, for example, chloride of whose watery solutions are more or less able to dissolve it. When too small a quantity of this salt is taken with the food. the bones lose more or less of their hardness and firmness, and fractures do not readily unite. Phosphate of lime. like the phosphates of the alkalies, is indis pensable to cell-formation; and in the mantle of the mollusks (where new cells for the formation of shell abound) this salt is far more abundant than in any other part of the 11011y. Although by far the greater of the phosphate of lime found in the body has doubtless preexisted in the food. yet it is unquestionable that a part of it is formed within the organism by the action of !carbonate of lime on the phosphoric avid that is formed during the disintegration of the phos phorus.containing tissues, such as the brain. In
man and carnivorous animals, a certain portion of the phosphate of lime is eliminated by the kid neys. and the rest is carried off in the excre ments: while in herbivorous animals the whole is carried off in the excrements. The acid phos phate of lime is occasionally found in the urine of man and carnivorous animals, but is of no practical importance. For the amount of earthy daily eliminated by the kidneys, see URINE.
or no ti phosphate of mag nesi PO,) is analogous, hoth in its chemical and physiological relations, to the corresponding salt of lime, with which it is atm a3's The abundance of this salt in cereals and vegetables explains its presenee in the system. A far less amount of Mils salt than of the corresponding lime-salt seems to he required] by the organism, as is shown by the relative quantities in which they occur in bone (57 of the former to 1.3 of the latter t. and as is further indicated by the fact that. relative ly. far of this than of the lime-salt escapes intestinal absorption, and appears in the excre ments.
I The only phosphates remaining to be noticed are the of urn))))iet (toil nesiu , or triple phosphate, edIP.which oc curs in beautiful prismatic crystals in alkaline urine and urine that is beginning to putrefy, and the phosphate of soda. and ammonia, which is found as a crystalline sediment, in putrid urine.