The successful researches of Robiquet in his labors on the Cantharis Vesicatoria, have demonstrated that the cristallisable neutral substance to which he gave the name of _Cantharidine_, is the proximate epispastic principle of the blistering cerate on which the physician depends in most cases, where an extended and yet deep revulsive action is necessary, whether it is derived from the cantharis vesicatoria or from other members of the trachelid family. The experiments of Mess. Lavini & Sobrero of Turin, have confirmed the supposition made by analogy, of the indentity which exists in the vesicating principle of all these coleopters, and there is a strong presumption that our commerce will soon be enriched with the beautiful cantharis, (C. nutalli,) abounding in the midst of our rising South Western States, and that it will eventually supersede the cantharis vesicatoria we obtain from abroad. If adulteration would not destroy, by its baneful influence, the advantageous form of complex extracts, we could obtain a desirable amelioration of our officinal cerate, by substituting for the powdered cantharides an equivalent proportion of the oleaginous liquid, with which they are saturated in the fresh state, and which is possessed of all the vesicating properties of the insect. That liquid is prepared in various parts of the Sardinian kingdom, especially at Verceil, where it is extensively used by veterinary surgeons in preference to the preparations from the powdered insect, it { 73} producing deeper revulsion. It is also used, diluted in bland oleaginous substances for stimulating the activity of feeble serous exudations. As for the present we have not generally access to that natural product of the cantharis, we must select those insects in the best possible conditions, and endeavor to fix their active principle in such a manner as will diminish the liability to spontaneous volatilisation of which it is susceptible, even at ordinary temperature.
I have been for many years in the habit of preparing a blistering plaster which, I think, has some advantages over our officinal cerate, because it fixes the volatilisable principle, and at the same time rather increases than diminishes its energy.