To determine the manner in which mercury acts on the venereal virus, it might seem requisite that the nature of this poison should first be ascertained. In what the activity of the venereal virus consists, it is difficult, perhaps impossible, to say. Various conjectures have indeed been offered with regard to it. But what has hitherto been advanced upon that subject is so hypothetical as scarce to deserve a serious refutation. What could, therefore, be derived from an inquiry of this nature, without a more perfect knowledge of the subject than has hitherto been attained, would be but of little utility. But, although the peculiar nature of the venereal virus, and those principles in consequence of which it becomes active, are unknown, yet its general effects, as acting on different parts of the human body, are sufficiently obvious. The parts morbidly affected by the venereal virus, at different times, put on different appearances. This, however, is in common to all of them, that, when reduced to the state of an open ulcer, they discharge an infectious matter capable of propagating the disease. It cannot therefore be doubted, that the venereal matter occasions the morbid affections there observed from its actual existence at these places. As the places evidently affected by the venereal poison are frequently very distant from those to which the poison has been first applied, and do not lie in the course of the absorbents, it can only be carried to them in the course of circulation. But, even while the poison is present in the circulating system, no change can be detected on the general mass of fluids; nor in by much the greater part of the solids in the body. Many changes may take place in the fluids of the human body which cannot be said to constitute a diseased state. That such changes may be esteemed morbid, it is necessary that they should manifest themselves over the system in general. If, then, we are to judge by these principles, it follows, that the venereal poison does not produce a morbid state in the general mass of fluids. It evidently acts as a cause of disease in particular parts, whether it first comes to be applied to these by immediate contact with external objects, or arrives at them in the course of circulation. Probably it acts as a morbid cause in these places, from being, by some accident, detained there, in consequence of which the quantity of the poison is increased by assimilation. This opinion, with regard to the influence of the venereal virus in producing the disease, will lead to a different conjecture concerning the operation of mercury, as tending to destroy it.