It is indeed true, that much benefit has been alledged to be obtained from guaiac in the cure of the _lues venerea_. Experience, however, has sufficiently demonstrated, that these testimonies are not altogether to be relied upon. The influence of guaiac may perhaps be very considerable in certain stages of _lues venerea_, when the malignity of the disease is already overcome by means of mercury; or in particular climates, where the nature of this infection seems to be in some degree different from what it is in this country. But, how far the good effects of guaiac are established by facts in this climate, and before a cure has been attempted by mercury, is still a matter of great doubt. And, at any rate, even the most sanguine advocates for the use of guaiac will allow, that the good effects obtained from its use are by no means to be put in competition with those which are derived from the employment of mercury. But, even admitting all that has been said in favour of guaiac to be strictly true, still it does not follow, that it cures the _lues venerea_ by evacuation. Many medicines which operate much more powerfully as evacuants have no such effect. And, what was formerly said with regard to the cure of _lues venerea_, being proportioned to the evacuation produced by mercury, may perhaps, with equal justice, be applied to guaiac. It cannot be, with certainty, concluded, that the evacuation in either case is to be looked upon as the cause of the cure, since, in both, it may only be its concomitant. From this argument, then, nothing can be inferred, which has any tendency to establish the truth of the theory in support of which it is adduced. Thus have we examined the different arguments used in favour of the supposition, that mercury cures _lues venerea_ by acting as an evacuant. And, from this examination, it appears, that they admit of satisfactory answers. What has then been said in proof of the theory, can by no means be considered as sufficient to establish its truth. But the insufficiency of the arguments adduced in support of it, is not the only reason for not adopting it. There are many objections to this hypothesis, which would have been sufficient for rejecting it, even supposing that the arguments brought to prove it had been such, that no falacy in them could have been detected. That this theory, then, may, with less hesitation, be set aside, it will be necessary to mention a few of these objections.