That mankind were, in a very early stage of their existence, not only acquainted with the deadly effects of certain natural substances when applied in minute quantities, but that they availed themselves of such knowledge for the accomplishment of the worst purposes, is very satisfactorily shewn by the records of sacred as well as profane authors. But such is the ambiguity of ancient writers upon this subject, and so intimately blended are all their receipts with the practices of superstition, that every research, however learned, into the exact nature of the poisons which they employed, is necessarily vague and unsatisfactory. Of this one fact, however, we may be perfectly satisfied, that they were solely derived from the animal and vegetable kingdoms, for the discovery of mineral poisons was an event of later date; owing however to the defect of botanical nomenclature, it is even doubtful whether the plants which are designated by the terms _Cicuta_, _Aconitum_, &c. in ancient authors, were identical with those we designate by the same names. (See _Pharmacologia_, edit. v. vol. 1, p. 66.) With respect to the poisons of _Locusta_, all cotemporary writers speak of the venom of the toad as the fatal ingredient of her potions, and in the Alexipharmaca of _Dioscorides_ we find the symptoms described, which are said to be produced by it;[123] but what is very extraordinary, the belief of the ancients on this matter was all but universal. _Pliny_ is express on the subject; _Ætius_ describes two kinds of this reptile,[124] the latter of which, as Dr. _Badham_ has suggested, was probably the frog, as well from the epithet, as that he ascribes deleterious powers only to the former. It is scarcely necessary to observe that this ancient belief has descended into later times; we find Sir _Thomas Browne_ treating such an opinion as one of the vulgar errors; and we have before alluded to the legend of king _John_ having been poisoned by a wassail bowl in which matter extracted from a living toad was said to have been infused. In still later times, we have heard of a barrel of beer poisoned by the same reptile having found its way into it. _Borelli_ and _Valisnieri_ maintain that it is perfectly harmless, and state that they had seen it eaten with impunity. _Spielman_[125] expresses the same opinion, “_Minus recte itaque effectus venenati a bufonibus metuuntur._” _Franck_,[126] on the contrary, accuses _Gmelin_ of too much precipitancy in rejecting the belief respecting toad-poison,[127] Modern naturalists recognise no poisonous species of toad; even the most formidable of the species, to appearance, that of Surinam, is said to be perfectly harmless.