For many years after its introduction into practice, it was confined to a few diseases. At length it occurred to physicians, that a remedy, which in these proved so efficacious, might produce similar effects in other cases; and such has been the success of the trial, that during the last twenty years mercury has been coming into general use, with a rapidity unequalled in the history of any other medicine. But the more we are assured of its value, the more cautious we ought to be in its employment; both because it is of the greater consequence to prevent any prepossession against it, and because we know that there is no active medicine which can safely be trifled with. The prejudices which prevail against the use of mercury seem to arise from three sources; the nature of the complaints in which it was first employed; the uneasiness which even its salutary operation, when carried to a certain extent, necessarily occasions; and the bad consequences which sometimes attend an improper use of it. It is surprising, that the first of these causes should operate against its use; yet such is the confusion which naturally creeps into our ideas on subjects in which we are not habitually interested, that the prejudices of not a few originate from this cause. Of such a prejudice it is surely unnecessary to say any thing. The other objections to the use of mercury are of more weight. Like all other medicines which increase the secretion by the skin, the use of mercury tends to debilitate, and render the body more susceptible of cold. When mercury does not encrease any other excretion, the debility it occasions seems to be proportioned to the degree in which it promotes perspiration; and medicines which promote perspiration in a greater degree produce more sudden debility. We see a degree of weakness produced by the operation of James’s powders, or of Dover’s powders, (opium and ipecacuanha), in a few days which a moderate course of mercury would not occasion in many weeks. Such is the tendency of mercury to promote the secretion by the skin, that it often runs off in this way almost as fast as it is received into the system, particularly on its first being used; so that it is sometimes difficult to make a sufficient quantity be retained to produce its desired effect. Some of the good effects of mercury seem, in a great measure, to arise from this action of it, particularly its tendency to counteract the inflammatory disposition and to relieve actual inflammation.