PHOSPHATES (from phosphorus) (in physi ology). The following phosphates play an active part in the chemistry of the animal body.
Phosphate of coda occurs in three forms.NaPO„ Na,EPO,, and in NaTI,PC).. called respeetiv(ly the basic, neutral. and acid salts. These are all soluble in water. fly exposing the second of these salts to a red heat pyropriosphate of soda, Na,P?i„ is formed, and by similarly treating the third, no taphosphoc, results. Phosphate of soda in one or the other of the above forms is a constituent of all the lluids and soft tissue- of the body, and is espeeially abundant in the urine and bile. Pyrophosphate and metaphosphate of soda are found in the ashe- of animal tissues after incineration, but they result merely from the ac tion of heat on the neutral and acid salt-. The salts of sodium are always associated with the corresponding salts of potassium, and what is said of the derivation. elimination, and physio logical importance of the one is equally applicable to the other. The alkaline phosphates obviously are derived from the food, being either ingested a such or converted within the organism from other alkaline salts. Elimination is effected chiefly through the kidneys and intestinal canal. In the carnivorous animals, whose blood is much richer in phosphates than that of herbivora (the ash of the blood of the dog, for example. from 12 to 14 per cent. of phosphoric. acid. while that of the ox or sheep does not contain more than from 4 to 0), these salts are carried off the urine; but in consequence of the formation of free acids as products of the disintegration of the tissues, a portion of the base is abstracted from the originally alkaline phosphates, and a corre sponding portion of phosphoric acid is liber ated. The originally alkaline salt is thus ren dered neutral or even acid : and the occurrence of the acid phosphate of soda. in the urine is thus explained. In the herbivorous ani mals, on the other hand. the urine no phosphates. the whole of the phosphoric acid taken in their food being eliminated by the intes tinal canal in the form of the insoluble phos phates of lime and magnesia. Although the gen
eral distribution of the phosphates of the alkalies in the nutrient fluids I there is 40 per cent. of theta in the ash of the blood-cells: 28.4 per cent. of phosphoric acid and 23.5 of potash in the ash of cow's milk: and about 70 per cent. of phos phoric acid in the ash of the yolk of egg) is in it self an indication of their importance. the exact nature of their function- is not completely under stood. Liebig has specially drawn to 1 he peculiar grouping of the acid and alkaline fluids of the animal body. The permanence of this grouping is chiefly maintained. especially in herbivorous animals. by the conversion within the body of alkaline and neutral phosphates into acid phosphates by the means already described. Moreover. all tissue-forming substances (the pro tein bodies) are, so closely connected with phos phates that they remain associated during the solution and subsequent re-precipitation of these substances; and the ash of developed tissue, as muscle. lung. liver. etc.) always afford evidence that acid existed in the re cent tissue; and. further. no exudation from the blood-vessels can undergo transformation into cells and fibres. or. in other words. become or ttanized. phosphate: are present. Another proof of the share taken by the phosphates in the format ion and functions of tissue is the fact that. Althowth herbivorous animal: take up a very small quantity of phosphates in their food. and altlowth their blood is very poor in these salts. their contain a- large a proportion of hosphates as the corresponding parts of car nivora. Lastly, the fact that one equivalent of the alkaline phosphate of soda, pos sesses the property of absorbing as much carbonic acid as two equivalent, of carbonate of soda, leads to the belief that the power of attracting carbonic acid, which the strum of the blood pos sesses, is due as much to the phosphate as to the ea clionnte of soda, and that, consequently, phos phate of soda plays all important part in the res piratory process.