52 Exirad of Fourcroy and Vauquelin’s 
matter. 4. The oxalic acid, which is produced under fome 
morbific circumftances. 5. Siliceous earth, which is found 
in it only very rarely. ‘Fhe four firft fubftances are conftant 
in it; the other two are only accidental, and therefore we 
pafs them over till after the examination of calculi arifing 
neceflarily from urine, and of which the conftituent matters 
have been diffolved in that liquid. Another new fact ob- 
tained by our labour is, that the particular matter which 
gives to urine its diftinguifhing characters, is converted, by 
means of the fermentation excited by the prefence of the ge- 
latinous body, into ammonia, carbonic acid, and acetous acid, 
and from thefe new products there arife in urine very re- 
markable changes. The analyfis of putrid urine differs, there- 
fore, very much from that of frefh urine. 
It refults from thefe refearches, by which human urine 
has become much better known than it was before, that it 
contains ten pr incipal or canftant fubftances, characterifed in 
the following manner ; 
A. Muriat of foda, which cryftallifes jn oCtaedra in eva- 
porated urine. 
B. Muriat of ammonia; the natural o¢taedral form of 
which is modified into a cube by its unjon with the parti- 
cular urinary matter like that of the preceding, and pafles 
through the fame combination from the cube ta the otta- 
edron, 
C. The acid phofphat of lime, forming about the 7ooth 
part of urine, confidered formerly as an earth, precipitating 
itfelf by the addition of alkalies, which take from it its excefs 
of acid ; carrying always with it a gelatinous matter which 
this acid held in folution, and rendering urine turbid at the 
moment when the ammonia is difengaged. 
D. Phofphat of magnefia, decompofed by alkalies, and 
giving its earth mixed with the phofphat of lime which is 
depofited ; becoming a triple falt, and feparating itfelf in 
cryftals by the fpontancous formation of ammonia. 
E, The phofphat of foda, efflorefcing in the air, and always 
united to the phofphat of ammonia. 
F. The phofphat of ammonia, little abundant when the urine 
is freth 5 increafing much by decompofition and the jorma; 
tion 
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