316 
ON VESICATING APPLICATIONS. 
the trees, in which these insects are, at this season more par- 
ticularly, are very apt to be attacked with opthalmia and 
ardor urinse."* 
In the Ann. de Chimie of the year 1804, Deyeux, has 
communicated the result of Beaupoil's examination of Cantha- 
rides; which differs in some respects from that of Thouvenel. 
Beaupoil found that the aqueous decoction of Cantharides, 
when mixed with alcohol or with ether, separates into two 
parts, nearly equal; the one in the form of a black glutinous 
precipitate, insoluble in alcohol, and the other a yellow-brown 
matter which alcohol takes up very readijy. He found that 
both these products, when applied to the skin, produced blis- 
tering in nearly the same time; and that the green concrete 
oil, to which Thouvenel ascribed all the blistering property of 
the fly, took no effect when applied alone, but caused blistering 
when mixed with wax. 
These discrepancies remained unexplained until the year 
1810, when Robiquet made known the details of his more 
accurate and satisfactory analysis of Cantharides. His ex- 
periments bear so forcibly upon the principles under con- 
sideration, that they appear entitled to a more detailed 
account than is met with in those elementary works which 
allude to them. 
Adopting the same means of extraction, by water, alcohol, 
and ether, as the preceding experimenters, Robiquet proceeded 
as follows: Cantharides, in powder, were boiled with repeated 
portions of distilled water until nothing further was yielded 
to the liquid. The residue of the flies, was next treated with 
alcohol, and the tincture thus formed, on evaporation, afforded 
a green oil similar to that obtained by Thouvenel and Beaupoil 
This oil was found to possess no vesicating properties. The 
decoction was now carefully evaporated to the consistence of 
a soft extract. It possessed the vesicating quality of the fly 
in a powerful degree. Boiling alcohol added to this took up 
a yellow matter and left a black glutinous residue. This 
* Materia Medica, Part II., page 1368. 
