4 4 Dr. Pearson's Experiments and Observations 
as the calculi from the stomach and intestines of the same ani- 
mal) of phosphate of lime, phosphate of ammoniac, and com- 
mon animal matter, which melted like superphosphate of lime, 
after burning away the animal matter and ammoniac. As 
these, and some other experiments, seemed to concur in esta- 
blishing an important truth, I thought it necessary to examine 
an urinary concretion of a horse, which, from its figure and 
size, was unquestionably from the kidney of that animal; for I 
have found by experience, that one cannot depend entirely on 
the accounts in cabinets, nor indeed, sometimes, on the asser- 
tions of persons who collect specimens. 
1. This concretion, which Dr. Baillie was so good as to 
give me, was of a blackish colour, was very brittle and hard, 
and had no smell or taste. It felt heavier than human urinary 
calculi. 
2. Under the blowpipe it became quite black, and emitted 
the smell, weakly, of common animal matter. It was reduced 
very little in quantity, and showed no appearances of fusibility, 
after being exposed for a considerable time to the most intense 
fire of the blowpipe. 
3. .Muriatic acid dissolved this concretion, with effervescence, 
yielding a clear solution; which, on evaporation to dryness, 
left a black and bitter residue. 
4. A little of the residue (3.) being boiled in pure water, to 
the filtrated liquor superoxalate of potash was added ; which 
occasioned a very turbid appearance, and copious white preci- 
pitation. 
5. Nitric acid also readily dissolved this concretion, with ef- 
fervescence. The solution being evaporated, partly to dryness, 
and partly to the consistence of an extract, the dry residuary 
