440 THE URINE. 



Inorganic Constituents. The inorganic ingredients which 

 occur in the urine are mainly in the form of chlorids, phosphates, 

 sulphates, and carbonates, combined with sodium, potassium, 

 ammonium, calcium, and magnesium, and are excreted to the 

 amount of about 25 grams per diem, of which about 15 grams are 

 sodium chlorid, derived almost exclusively from that taken in 

 with the food. 



The inorganic constituents eliminated in the urine come from 

 (1) the inorganic constituents of the food, and (2) from the de- 

 structive metabolism of the body -tissues. In the first group are 

 the chlorids and the principal part of the phosphates; in the 

 second, the sulphates, which occur in but small quantities in the 

 food, and a small part of the phosphates. 



Chlorids. Although the urine contains some potassium chlorid, 

 it is mainly by sodium chlorid that these salts are represented. 

 Inasmuch as its quantity in the urine depends upon that taken 

 in with the food, this is subject to considerable variation. In 

 disease any process which results in taking sodium chlorid from the 

 blood will correspondingly diminish its excretion in the urine ; 

 this occurs in the exudations which accompany pneumonia and 

 pleurisy. When these are absorbed, the chlorid of sodium again 

 enters the blood and the quantity in the urine is increased. 



Phosphates. In the metabolism of the tissues of the body 

 some of the phosphorus contained in nuclein, lecithin, and prota- 

 gon is oxidized, producing phosphoric acid, which in the form of 

 phosphates is excreted in the urine ; the amount of this is, how- 

 ever, small. Most of these salts which occur in the urine are 

 derived from the food ; hence their quantity is increased with an 

 animal diet, while with a vegetable diet it is diminished. The 

 phosphates of plants are not absorbed by the animal, because of 

 their insolubility, hence in the urine of herbivorous animals these 

 salts are deficient. The amount of phosphoric acid daily excreted 

 in human urine is about 3.5 grams. 



The phosphates exist in two forms : (1) Alkaline and (2) 

 earthy. The alkaline phosphates are those of sodium and potas- 

 sium ; while the earthy phosphates are those of calcium and mag- 

 nesium. 



Sodium dihydrogen phosphate, also called acid sodium phos- 

 phate, NaH 2 PO 4 , is the principal factor in giving urine its acid 

 reaction, although associated with it in this office is calcium 

 dihydrogen phosphate, Ca(H 2 PO 4 ) 2 . When the reaction of the 

 urine is neutral there are also present disodium hydrogen phos- 

 phate, Na 2 HPO 4 , calcium hydrogen phosphate, CaHPO 4 , and mag- 

 nesium hydrogen phosphate, MgHPO 4 . When the urine is alka- 

 line these may also be present, accompanied by the normal phos- 

 phates, Na 3 PO 4 , Ca 3 (PO 4 ) 2 , Mg 3 (PO 4 ) 2 , or these latter may replace 

 the former. 



