134 On the Compofition and Properties 
treafure offered me, what I could not have taken the hberty 
of requefting, namely, permiffion to break off pieces from 
any of the articles, for experiment. Mr. Edward Howard 
did me the honour to take upon himfelf the tafk of writing 
down the reports, and otherwife affifted me. 
At this time I fhall only mention, 
1. That out of 200 {pecimens of urinary calculi, not more 
_ than fix did not contain the animal oxide above deferibed, 
“4. e. about 32 out of 33 contained it. 
a. That the proportion of this oxide was very different ; 
varying from =4, (exclufive of water,) to 122; but, for the 
moft part, varying between 2°, and 49 *, 
3. That the common animal tan ove of urine is free 
quently found in concretions, in very different proportions 3 
but is perhaps never a principal conftituent part of them. 
4. That the above animal oxide was not found ia the uri- 
mary concretions, or any other concretions, of any animal 
but the human kind. 
5. That this animal oxide was found alfo in human ars 
thritic calculi, but not in thole of the teeth, ftomach, intef- 
tines, lungs, brain, &c, 
P. S. I think proper to fubjoin a few experiments, made 
after the preceding paper was written, which afford evidence 
of the truth of fome of my conclufions, and enable us to ex- 
plain fevera] properties of animal concretions. 
I. On an Urinary Concretion from a Dog. 
This calculus may be faid to be a great curiofity, for it is 
probably the only fpecimen in London. I owe the opportu- 
nity of examining it to Mr, H. Leigh Thomas, who met. 
with it in the courfe of his diffeétions; and therefore we 
have unqueftionable authority, that the concretion was 
** In fome urinary concretions, the interior part contained this oxide, and 
the exterior part had none of it. On the contrary, in other urinary con- 
eretions, the extcrior part contained it, and the interior partdid not. 
really 
