Observations on the Operation and Use of Mercury in the Venereal Disease

by Andrew Duncan

The degree of evacuation which, in any case, arises from the employment of mercury, will, it is natural to imagine, be proportioned to the quantity of active mercury which is introduced into the system. But, in whatever way mercury acts in the cure of the venereal disease, it may then be supposed to act most powerfully when it is present in the system in most considerable quantity. In this point of view, then, the evacuation which arises from the use of mercury is to be considered merely as an index of the quantity of the medicine which is introduced into the system in an active state; and the cure may be proportioned to the evacuation, only as pointing out the degree in which the mercury exists in the habit. Even supposing, then, that the foundation upon which this argument is built were not to be called in question, yet, taken in its greatest latitude, it is still at best but doubtful; and from it no conclusion can be drawn in favour of the theory which it is brought to support.

The second argument mentioned in proof of the supposition that mercury acts, in the cure of lues venerea, as an evacuant, was, that the cure produced by mercury depends more upon the stimulant power of the preparation employed, than upon the quantity of mercury which is used.

This argument may be answered in the same manner with the preceeding. It is indeed true, that different preparations of mercury, when used in equal quantities, have by no means equal influence in the cure of lues venerea. There is seldom an opportunity of observing what would be the effects of the most stimulant preparations, as, in the venereal disease, they are by no means in common use; and as, from their action on the alimentary canal, they exert very violent effects, without entering the circulating system. They, in general, operate very roughly, both as emetics and purgatives; but it is not clear that, in the venereal disease, any benefit has been obtained from their effects in either of these ways. It can therefore by no means be allowed, that the foundation of this argument, in its full extent, is strictly true. It cannot indeed be denied, that some preparations of mercury, which possess a considerable stimulant power, have a greater influence in the cure of lues venerea, than several others which are less stimulant. So far, then, the foundation upon which this argument is built, must be allowed to be just, and its weight, as tending to establish this theory, requires a refutation.

But, even admitting it to be just, without any reserve, still, no more than from the former, can any conclusion be drawn from this in favour of the theory which it is meant to support. It has already been observed, that, in whatever way mercury operates in the cure of lues venerea, its good effects may always be supposed to be proportioned to the quantity of the medicine which enters the system in such a state as to become active there. But the quantity of active mercury entering the system can in no case be judged of from the quantity of the preparation which is employed. One preparation of mercury much more readily admits of a mixture with the animal fluids than another; in consequence of this, it will find a more ready entrance into the system. And further, this variety in the facility of access into the system, not only holds in different preparations, but even in the same preparation at different times.

In proof of the first of these propositions, we have a convincing example in the difference which is observable between the effects arising from the use of crude mercury, and of this metallic substance, when no other means are used to render it active than simple trituration. It is well known, that even a very inconsiderable quantity, taken in this last way, will soon shew its effects at the most remote excretories of the body; in the other, although swallowed to the quantity of many pounds, it is a very rare occurrence that any effects can be observed from which it can be concluded, that it has, in any degree, entered the mass of circulating fluids.

But it was likewise alledged, that mercury, used at different times, although given in equal quantities and in the same form, produces very different effects. Crude mercury, as has already been observed, although swallowed in considerable quantities, rarely produces any other effect on the body, than what arises from the passage through the alimentary canal. This, however, although generally, is not universally the case. On some occasions, when taken in this way, it operates with as great activity as when used in any other form; and, from many well attested instances, it appears, that, by being swallowed even in a crude state, a high salivation has been excited. In this we have an instance in which a remarkable difference of effect arises from the employment of the same preparation at different times. This difference cannot arise from the quantity of mercury employed; for while, in some cases, no operation of the nature here mentioned takes place from the use of a large quantity, in others, it will be excited where an inconsiderable quantity only has been taken. The difference of effects here observed, then, must be ascribed to some other cause; and it is most reasonable to refer it to particular accidents in the constitution at the time the medicine is used. In these cases, where no operation takes place from its use, it may be concluded, that the whole quantity of mercury swallowed has passed through the alimentary canal in the same state in which it was taken in. When, on the other hand, an operation upon the salivary glands, or any other excretory remote from the alimentary canal, is observed from the use of crude mercury, it may be concluded, that part of the mercury, from some peculiarity in the habit at the time, such, for example, as the presence of superabundant acid in the stomach, has been brought into such a state as to be capable of entering the circulating system. From these instances, then, it evidently appears, that the facility with which mercury enters the system, admits of very great variety. And from this a strong objection may be adduced against the argument here brought to support the hypothesis that mercury cures lues venerea by its evacuant power.

It is alledged, that mercury cures lues venerea by the evacuation it occasions; because the good effects derived from its employment are observed to be more in proportion to the stimulant power of the preparation which is used, than to the quantity of mercury taken. The data, however, here assumed by no means lead to the conclusion deduced from thence. The most stimulant preparations of mercury, by their action on the primæ viæ, are in general immediately expelled from the system. When this happens, they have no influence in the cure of venereal complaints. When they are not thus expelled, their nature is such that they most readily enter the system. Their superior action, then, may be accounted for without supposing that it depends on their producing the most considerable evacuation.

From the facts as here stated, it indeed follows, that the good effects obtained from mercury are greatest in those cases in which the mercury enters the system in most considerable quantity. The evacuation, it is true, is then likewise greatest. But this will unquestionably follow as the necessary consequence of the presence of active mercury in the system, and can by no means be concluded to be the cause of the cure. The evacuation which occurs in this case, then, as was observed in the objections adduced against the last argument, can be considered only as an index of the quantity of active mercury which is present in the system. The superior activity, therefore, which some stimulant preparations possess, when compared with those of a milder nature, is by no means a proof of the supposition that mercury cures lues venerea by means of the evacuation which it produces; and this argument, as well as the former, may be set aside.

The third argument mentioned in favour of this theory, and the last which we proposed to consider, is, that the same good effects, in the cure of lues venerea, may be obtained from the employment of other evacuants, as from that of mercury; and particularly, that the venereal disease is cured in a similar manner by the use of guaiac.

This argument, if well founded, would indeed be a conclusive proof of the theory, in support of which it is here adduced. Evacuation may be occasioned by a great variety of other means besides mercury. The influence of any discharge, as tending to cure lues venerea, will fall more particularly to be considered in stating the objections against this theory. A full answer, then, to the first part of this argument, would at present be superfluous: But it may be observed, that it is by no means a common practice to attempt the cure of lues venerea by the safest and most effectual evacuants now in use; and that, when evacuants are employed for the cure of other diseases, while a venereal infection at the same time exists in the system, it is never found to yield to them. This first part of the argument, then, may be shortly answered, by denying it to be true.