152 THE LACTATES, AND UREA AS IT EXISTS IN URINE. 
ed, which, purified by boiling water, gave, on evaporation, 
handsome prismatic crystals of hippuric acid. 
3. By a slight excess of baryta. Alcohol of 40° was then 
added, and the liquid, after filtration and evaporation, deposit- 
ed yellow crystals, which nitric acid changed in the super-ni- 
trate of urea. The deposit not taken up by the alcohol, treat- 
ed with hydrochloric acid and boiling water, on being filtered 
and evaporated, yielded crystals of hippuric acid. The hip- 
purate of urea, artificially prepared and submitted to similar 
operation, presented characters which were entirely identical. 
Experimentsof the same kind were made with the urine of the 
horse with like results, except only that the volatile principle 
of the products exhaled the odor peculiar to the horse, and not 
to the cow. This odor, which is foreign to the hippuric acid, 
appears to proceed from a volatile resinous principle. 
We were desirous of extending these researches to the ex- 
cretions of birds and serpents. One of us had in possession a 
certain quantity of the excrements of the boa. We triturated 
these with pure baryta and a little distilled water, and, after 
moderately drying the mass, treated it with alcohol of 40°. 
The liquid, filtered and evaporated, gave, as a residue, a mat- 
ter which nitric acid converted into supernitrate of urea. This 
latter principle was separated by means of carbonate of potassa 
and absolute alcohol. Urea had not been before noticed as 
one of the constituents in the excretory matters of reptiles. 
Finally, the dried dung of the pigeon and the canary bird 
was moderately heated with distilled water and hydrate of ba- 
ryta ; there resulted a mass which was dried and subjected to 
alcohol of 40°. The alcoholic solution was deprived of any 
slight excess of baryta by means of carbonic acid, and then 
distilled. The residue, of a yellowish white color, treated 
with nitric acid, gave rise to supernitrate of urea. The baryta, 
separated by the filter, retained, as in the preceding case, 
much uric acid, which allowed of no doubt but that the urea 
existed in the state of urate ; retaining the name uric acid, 
but which M. Liebig now considers as a combination of urea 
with a peculiar acid or a radical. 
