362 



EXCRETION. 



Pier. 117. 



soda and magnesia. One of these is the "triple phosphate," phos- 

 phate of magnesia and ammonia (2MgO,lSrH 4 0,PO 5 4- 2 HO). The 

 other is the phosphate of soda and ammonia (NaO,NH 4 0,HO,PO o 4- 

 8HO). The phosphate of magnesia and ammonia is formed from 

 the phosphate of magnesia in the urine (3MgO,P0 5 -f 7HO) by 

 the replacement of one equivalent of magnesia by one of am- 

 monia. The crystals of this salt are very elegant and charac- 

 teristic. They show themselves throughout all parts of the mix- 

 ture ; growing gradually in the mucus at the bottom, adhering to 



the sides of the glass, and 

 scattered abundantly over 

 the film which collects upon 

 the surface. By their refract- 

 ive power, they give to this 

 film a peculiar glistening 

 and iridescent appearance, 

 which is nearly always visi- 

 ble at the end of six or seven 

 days. The crystals are per- 

 fectly colorless and transpa- 

 rent, and have the form of 

 triangular prisms, generally 

 with bevelled extremities. 

 (Fig. 117.) Frequently, also, 

 their edges and angles are 

 replaced by secondary facets. 

 They are insoluble in alkalies, but are easily dissolved by acids, 

 even in a very dilute form. At first they are of minute size, but 

 gradually increase, so that after seven or eight days they may 

 become visible to the naked eye. 



The phosphate of soda and ammonia is formed, in a similar 

 manner to the above, by the union of ammonia with the phosphate 

 of soda previously existing in the urine. Its crystals resemble 

 very much those just described, except that their prisms are of a 

 quadrangular form, or some figure derived from it. They are 

 intermingled with the preceding in the putrefying urine, and are 

 affected in the same way by chemical reagents. 



As the putrefaction of the urine continues, the carbonate of am- 

 monia which is produced, after saturating all the other ingredients 

 with which it is capable of entering into combination, begins to 

 be given off in a free form. The urine then acquires a strong 



PHOSPHATE OF M A u N t: s i A AND AMMONIA; 

 deposited from healthy urine, duriug alkaline fermen- 

 tation. 



