THE CHEMISTRY OF THE ANIMAL BODY. 959 



example, the separate union of potassium with proteid and of phosphoric acid 

 with proteid, in the functionally active cell. However combined, phosphoric 

 acid is necessary for the organism. 



Detection. A solution of phosphate treated with a magnesium salt dissolved in am- 

 monia containing ammonium chloride, gives a fine crystalline precipitate of magnesium- 

 ammonium phosphate, which on ignition loses ammonia and is converted into magnesium 

 pyrophosphate. 



PHOSPHORUS IN THE BODY. The principal source of supply is derived 

 from the phosphates of the alkalies and alkaline earths in the foods ; it may be 

 absorbed in organic combinations in nuclein, casein, and caseoses ; and it may 

 further be absorbed as glycerin phosphoric acid, which is an intestinal decompo- 

 sition product of lecithin x and probably also of protagon. Phosphorus leaves 

 the body almost entirely in the form of inorganic phosphate, the only exception 

 being glycerin phosphoric acid, which has been detected in traces in the urine. 

 In man and carnivora the soluble primary and secondary phosphates of the 

 alkalies are found in the urine, together with much smaller amounts of the 

 less soluble primary and secondary phosphates of the alkaline earths. There 

 is likewise, even during hunger, a continuous excretion of tertiary phosphate 

 of calcium, magnesium, and iron in the intestinal tract. In herbivora the ex- 

 cretion is normally into the intestinal tract, and no phosphates occur in the 

 urine. This is because herbivora eat large quantities of calcium salts which 

 bind the phosphate in the blood, and they likewise eat organic salts of the 

 alkalies, which become converted into carbonate and appear in the urine as 

 acid carbonates ; such a urine has no solvent action on calcium phosphate. 2 

 In a similar manner a great reduction of phosphate in the urine of man may 

 be effected by feeding alkaline citrate and calcium carbonate, the first to furnish 

 the more alkaline reaction to blood and urine, the second to bind the phosphate 

 in the blood. The more alkaline reaction itself is insufficient to prevent the 

 appearance of phosphates in the urine. 3 On the other hand, starving herbiv- 

 ora, or herbivora fed with animal food, give urines acid from primary phos- 

 phate. 4 



Excreted phosphates may be originally derived from the phosphates of the 

 bones, or from phosphates arising from the oxidation of nuclein, protagon, and 

 lecithin, but by far the greater quantity is derived from the food, or from pro- 

 teid metabolism. In a starving dog, which feeds on its own proteid, it was 

 found that a ratio existed between nitrogen and phosphoric acid in the urine as 

 6.4:1, which approximates that in muscle, i. e. 7.6:1. On feeding meat till 

 nitrogenous equilibrium was established, the ratio became 8.1 : 1. 5 On addi- 

 tion of proteid to the body, a proportionate amount of phosphoric acid is re- 

 tained for the new protoplasm, while on destruction of proteid the phosphoric 

 acid corresponding to it is eliminated. The larger excretion of phosphoric acid 



1 Bokay : Zeitschrift fur physiologische Chemie, 1877-78, Bd. 1, p. 157. 



2 J. Bertram : Zeitschrift filr Biologie, 1878, Bd. 14, p. 354. 3 Op. tit., p. 354. 

 * Weiske : Ibid., 1872, Bd. 8, p. 246. 



5 E. Bischoff : Ibid., 1867, Bd. 3, p. 309. 



