THE LACTATES, AND UREA AS IT EXISTS IN URINE. 151 
viously freed from its first salts, are principally formed of lac- 
tate of urea. 
If we evaporate urine, rendered perfectly neutral by baryta, 
we obtain, after filtration, a liquid which, treated with etheri- 
sed alcohol and evaporated in the open air or in vacuo, deposits 
crystals of lactate of urea. This salt is accompanied, in healthy 
urine, by free lactic and phosphoric acids, of which the pre- 
sence may be readily recognised by the following process. 
Treat the brown product, resulting from the concentration of 
urine, with sulphuric ether ; there is thus separated a very 
acid liquid, which, evaporated and mixed with oxide of zinc 
and baryta, will give lactate of zinc and phosphate of baryta. 
The granular precipitate produced by ether is principally com- 
posed of lactate of urea. 
Being convinced that urea does not exist in human urine 
in a free state, but combined solely with lactic acid, we en- 
deavored to ascertain whether this principal was combined in 
the same manner in the urine of other animals. 
A certain quantity of the urine of a cow was evaporated to 
five-sixths in an alembic. The thick brown residue, sha- 
ken up with alcohol of 35°, gave rise to an abundant de- 
posit, of a grayish yellow color, containing hippuric acid and 
alkaline carbonates, which were separated by the filter. The 
alcoholic liquor, evaporated slightly, furnished a brown pro- 
duct, which soon became a pulpy mass ; this was express- 
ed, and after being purified by carbon and boiling alcohol, de- 
posited small needle-shaped crystals, which were neutral to 
test paper, and of a sharp, somewhat bitter, and slightly musky 
taste. 
This crystalline mass was treated 
1. By nitric acid. There was a slight effervescence, and 
there was obtained pearly, lamellar crystals of nitrate of 
urea, and long crystals of hippuric acid, (uro-benzoic acid of 
Berzelius.) 
2. By hydrochloric acid and heat. A musky odor was de- 
veloped, a brownish red deposit of a resinous aspect was form- 
