340 



FUNCTIONS OP NUTRITION. 



weather. The elements of two molecules of water unite with those of 

 urea to produce ammonium carbonate, as follows : 



Urea. 

 CH 4 N 2 O + 2H 2 O 



Ammonium carbonate. 

 (NH 4 ) 2 C0 3 



FIG. 84. 



The ammoniacal salt when first produced neutralizes a corresponding 

 quantity of sodium biphosphate, diminishing the acid reaction of the 

 urine. This diminution continues, as the fermentation proceeds, until 

 the acidity disappears altogether. The urine then becomes neutral, 



and subsequently alkaline ; its 

 alkalescence growing more pro- 

 nounced with the accumulation 

 of the ammoniacal salt. 



The time at which the urine 

 becomes alkaline varies with its 

 original degree of acidity and 

 the rapidity of its decomposi- 

 tion. Urine which is neutral 

 at the time of its discharge, 

 becomes alkaline more rapidly 

 than that which has at first a 

 strongly acid reaction. In sum- 

 mer, it is often alkaline on the 

 third, fourth, or fifth day ; while 

 in winter, if kept in a cool place, 

 it may still be neutral at the 

 end of fifteen days. In paraly- 

 sis of the bladder with cystitis, 



where the vesical mucus is increased in quantity and altered in quality, 

 and the urine remains in the bladder for ten or twelve hours at the 

 temperature of the body, it may be distinctly alkaline and ammoniacal 

 at the time of its discharge. In these cases it is acid when secreted, 

 but becomes alkaline while retained in the bladder. 



The first effect of the alkaline condition of the urine, thus produced, 

 is a precipitation of the earthy phosphates. This deposit slowly settles 

 on the sides and bottom of the vessel, or is partly entangled with certain 

 animal matters, forming a thin, opaline scum on the surface. There are 

 no crystals at this time, the deposit being entirely amorphous and gran- 

 ular. 



The next change is the production of a new salt, the ammomo-mag- 

 nesian phosphate, by the combination of ammonia, formed from urea, 

 with the magnesium phosphate already present in the urine. This 

 change is represented as follows : 



Magnesium phosphate. Ammonia. Ammonio-magnesian phosphate. 



MgHP0 4 + NH 3 MgNH 4 P0 4 



The crystals of this salt show themselves throughout all parts of 

 the mixture, entangled in the mucus at the bottom, adhering to the 



CRYSTALS OF AMMONIO-MAGNESIAN PHOSPHATE, 

 deposited from healthy urine, during the alkaline 

 fermentation. 



