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.