If this opinion be true, the venereal poison may be supposed to be productive of disease, only when collected at particular parts. This would lead us to conclude, that, if mercury possess a power of destroying the venereal virus when it comes in contact with it, it can only produce a cure of _lues venerea_ from being topically applied to the poison collected at particular parts of the body. Mercury, however, unquestionably does produce a cure of the venereal disease. If, then, it can be shewn, that mercury in reality is an antidote to the venereal virus; and that, previous to its producing a cure, it is topically applied to those parts in which the venereal virus is lodged, we may reasonably conclude, that the cure obtained from its use is to be referred to its action as an antidote from topical application. To establish this supposition, then, it is first necessary to show, that the mercury is in reality topically applied to the venereal matter. Many medicines, taken into the alimentary canal, are known to have the most powerful effects in the cure of diseases very remote from thence. While this happens, there are the strongest reasons for believing, that the medicine itself never passes the alimentary canal, or is in any respect introduced into the system. In such cases, therefore, it evidently produces a good effect on parts to which it is never applied. It may then occur, as a possible supposition at least, that this likewise may be the case with mercury. Mercury indeed produces many good effects by its action on the _primæ viæ_. But, when it is given in any of those forms in which it is of service in the venereal disease, those cases excepted where it is immediately applied to the diseased part itself, various phænomena tend to prove, that it actually does enter the mass of circulating fluids. It is only, from the introduction of mercury into the system, that various actions which it exerts in different parts of the body can be accounted for. Thus, for example, when it excites salivation, whether from being taken by the mouth, or from being rubbed upon the extremities most remote from the salivary glands, there is every proof which can be required that the mercury is actually present at these glands. The taste alone is sufficient to evince this. From the same mark also, we may be assured of the presence of mercury in the mouth, even when it is not introduced into the system in such a quantity as to excite salivation.