This substitution of one excretion for another, if I may use the expression, is particularly apt to occur under the use of mercury, and seems to arise from the nature of this medicine being so stimulating that we cannot retain it in the system: if one vent is denied it, it quickly finds another. Hence it is that people under the effects of mercury are so subject to an increased secretion from the kidneys and intestines, and from the glands of the mouth and throat.
It is of great consequence in most cases, in conducting a course of mercury, as much as possible to prevent its running off, and as we cannot wholly confine it, our plan is to direct it to that channel thro’ which it passes off most slowly; for it is well known that this and some other medicines, while they particularly excite any one excreting organ, are not apt to pass off at the same time in considerable quantity by any other. Now the channel by which mercury passes off most slowly is the glands of the mouth, and fauces. Our view, therefore, is generally to direct it to this channel, and the degree in which it increases the secretion from these glands is a sufficiently accurate measure of the quantity of mercury in the body, as we generally find that the effects of mercury in removing disease are proportioned to the degree in which it affects the mouth. Besides the discharge, and consequently the debility, occasioned by the same quantity of mercury, is less when it excites these glands, than when it acts on the skin and bowels.
While it increases the secretion from the glands of the mouth and fauces, it irritates and inflames them, and the inflammation it excites when the quantity which passes in this way is great, often becoming considerable and spreading to neighbouring parts, much uneasiness is sometimes occasioned.
The symptoms of salivation form the chief of the bad effects, which are peculiar to this medicine. They are indeed unpleasant, but they are unattended with danger. It is rarely proper to induce them. A physician may practice for several years without meeting with one instance in which salivation is necessary; and the extent to which the older practitioners were accustomed on every occasion to carry the use of mercury, may be regarded as one of the greatest abuses which have opposed the beneficial employment of this medicine. It has certainly more than any other tended to confirm the prejudices against it. All its good effects can in most cases be obtained by slightly affecting the mouth, and keeping up this affection for a longer or shorter time, according as the complaint proves more or less obstinate.