THE NITROGENOUS PRINCIPLES OF URINE. 295 
of urine, suffers decomposition, and its elements, combin- 
ing with the elements of water, are completely transformed 
into carbonate of ammonia. 
Urea, Water. Carbonate of Ammonia. 
CO N,H, + 2H,O = 2(NH,), H,0,CO,. 
As we have learned from Way’s experiments, clay is 
able to remove from urine the “ferment” which occasions 
its putrefaction. 
Urea is abundant in the urine of all carnivorous and 
herbivorous mammals, and exists in small quantity in the 
urine of carnivorous birds, but has not been detected in 
that of herbivorous birds. 
Uric acid (C,H,N,O,)* is always present in healthy 
human urine, but in very minute quantity. It is the chief 
solid ingredient of the urine of birds and reptiles. Here 
it exists mainly as urate of ammonia.** The urine of 
birds and serpents is expelled from the intestine as a white, 
thickish liquid, which drics to a chalk-like mass. From 
this, uric acid may be obtained in the form of a white 
powder, which, when magnified, is seen to consist of mi- 
nute crystals. By powerful oxidizing agents uric acid is 
converted into oxalate and carbonate of ammonia, and 
urea. Peruvian guano, when of good quality, contains 
some 10 per cent of urate of ammonia. 
Hippuric acid (C,H,NO,)} is commonly abundant in 
the urine of the ox, horse, and other herbivorous animals. 
By boiling down fresh urine of the pastured or hay-fed 
cow to *|, its bulk, and adding hydrochloric acid, hippuric 
acid crystallizes out on cooling in four-sided prisms, of- 
ten two or three inches in length. 
* Carbon .......... 35.72  * Carbon......... 32.43 + Carbon............ 60.74 
Hydrogen...,.... 2.38 Hydrogen...... 3.78 Hydrogen......... 4.96 
Nitrogen.........33.33 Nitrogen .......37.84 Nitrogen ........., %.82 
OxyPen..cevsayes 28.57. Oxygen........ 25.95 Oxygen ...........26.48 
