The ground or occasion of this expression might from hence arise, that Toads are sometimes observed to exclude or spit out a dark and liquid matter behind: which we have observed to be true, and a venomous condition there may be perhaps therein, but some doubt there may be, whether this is to be called their urine: not because it is emitted aversly or backward, by both sexes, but because it is confounded with the intestinal excretions and egestions of the belly: and this way is ordinarily observed, although possible it is that the liquid excretion may sometimes be excluded without the other.
As for the stone commonly called a Toad-stone, which is presumed to be found in the head of that animal, we first conceive it not a thing impossible: nor is there any substantial reason why in a Toad there may not be found such hard and lapideous concretions. For the like we daily observe in the heads of Fishes, as Cods, Carps, and Pearches: the like also in Snails, a soft and exosseous animal, whereof in the naked and greater sort, as though she would requite the defect of a shell on their back, Nature near the head hath placed a flat white stone, or rather testaceous concretion. Which though _Aldrovandus_ affirms, that after dissection of many, he found but in some few: yet of the great gray Snails, I have not met with any that wanted it: and the same indeed so palpable, that without dissection it is discoverable by the hand.
Again, though it be not impossible, yet it is surely very rare: as we are induced to believe from some enquiry of our own, from the trial of many who have been deceived, and the frustrated search of _Porta_, who upon the explorement of many, could scarce find one. Nor is it only of rarity, but may be doubted whether it be of existencie, or really any such stone in the head of a Toad at all. For although _Lapidaries_ and questuary enquirers affirm it, yet the Writers of Minerals and natural speculators, are of another belief: conceiving the stones which bear this name, to be a Mineral concretion; not to be found in animals, but in fields. And therefore _BÅtius_ refers it to _Asteria_ or some kind of _Lapis stellaris_, and plainly concludeth, _reperiuntur in agris, quos tamen alii in annosis ac qui diu in Arundinetis inter rubos sentesque delituerunt bufonis capitibus generari pertinaciter affirmant_.