When the mercury is thrown on the kidneys it passes off, as by the skin, without uneasiness of any kind; and as in this case also, the only bad consequences are, that the mercury, instead of acting on the system for the cure of the disease for which it is given, is drained from the body, and the patient is sometimes weakened by the increased discharge. Mercury may, to a certain degree, be diverted from the kidneys by the use of certain astringent medicines. Those which direct it to the skin, by increasing the action of this organ, will divert it from the kidneys; but by this we should lose, not gain, as it is thrown off by the former more rapidly than by the latter.
In many cases the action of mercury on the kidneys is salutary, and our aim is as much as possible, by the use of diuretic medicines, to direct it to this channel; for it happens with respect to the kidneys, as with respect to the bowels, that whatever tends to irritate and increase the discharge from them, solicits the mercury to them. It is partly in this way that it often proves a cure in various species of dropsy.
As far as we have considered the effects of mercury, its debilitating tendency seems to arise from the evacuation it occasions. But it debilitates in another way, which has not been sufficiently attended to. Whatever weakens the stomach and bowels is soon felt in every part of the system, and even medical men, as far as I can judge, are not in general sufficiently aware of the bad effects which often arise from the internal use of mercury. To prescribe calomel, one of the most active preparations of this medicine, with the same freedom, and for the same purposes, as rhubarb or senna, is in my opinion altogether a misapplication of it.
Few things apply to the stomach and intestines a more hurtful irritation. I have often seen temporary dysentery induced by a few doses of calomel, and I am convinced from many cases that its habitual or even occasional use as an aperient, however innocent it may seem at the time, seldom fails at length to debilitate the powers of digestion, and is often productive of still worse consequences. Calomel is frequently given to children because it has little taste, and may be given in small compass. But it is better to give a milder medicine, tho’ a larger quantity may be required. Perhaps the smallness of the quantity in which it operates is of itself a sufficient objection, for there is no aperient which operates in very small quantity that operates mildly, as we might have foreseen, although the trial had not been made. For my own part, I know of few instances in which the internal use of mercury seems proper. There are some cases where powerful means are required to rouse the bowels to action, or a strong stimulus applied to their exhaling vessels is beneficial; and mercury is sometimes successfully employed internally for the removal of worms, but in ordinary cases we can surely with equal advantage use a less irritating medicine.
When mercury is not employed as an aperient, but for the purpose of impregnating the system, what advantage is there in giving it by the mouth. It seldom happens that we cannot give as much as we wish by the skin. I have known many who were less debilitated by an ounce of mercury taken by the skin, than by half a dram received even in the smallest doses into the stomach.
In short, the objections to the use of mercury by the skin, seem all to resolve themselves into the two above treated of, the debility occasioned by an increase of some of the excretions, and a greater susceptibility to the effects of cold.[B] While there are the same objections to the internal use of mercury, there are far more weighty ones, which are not the less so, because we cannot with the same precision define them. All that we know of them is, that they chiefly consist in a debility of the stomach and intestines, which gives rise to the various dyspeptic complaints, flatulence, acidity, diarrhœa, and dysentery, effects which I have so often witnessed from the internal use of mercury, that I have for some years almost wholly abandoned it, except in the cases above alluded to.
[B] It is unnecessary to notice a variety of groundless opinions, respecting the effects of mercury, which prevail among the vulgar, that it remains for ever in the system, causes a rottenness of the bones, &c. These are similar to the prejudices which prevailed respecting the bark for a long time after its introduction into practice, that it was formed into masses in the stomach and bowels, from which it could never be expelled; that nobody survived the use of it more than seven years, &c.
The precautions suggested by what has been said will, I believe, in every instance, prevent the bad effects of mercury, with the exception of the symptoms of salivation, which it is now and then necessary to induce. It will be proper to take a cursory view of these precautions.