It will be most convenient to treat of the remedial uses of mercury, as its physiological effects have already been treated of, first in reference to its insensible or proper alterative action, and secondly to the influences it exerts in the state of full mercurialism.

A. Uses In Reference To Its Insensible Operation

It will be remembered that the influence of mercury, when given so as to produce no observable effect on the system, is exerted chiefly on the hepatic function; and the cause of this preference has been explained. it is with a view almost exclusively to its alterative action on the liver, that the medicine is used in this way. But, notwithstanding this limitation, it will be found that the varieties of morbid condition are not few, in which it proves highly serviceable. The immediate aim is to stimulate and regulate the hepatic secretion; but there are so many affections, which either have their roots in disorder of this function, or are greatly aggravated by it, that the curative effects of the remedy are greatly diversified. Besides, even when the liver itself is not in fault, the increase of its function may operate beneficially by depleting from the portal circulation, and thereby relieving congestion and irritation of all the abdominal viscera which are embraced in this circulation. The secretion of bile may be deficient, deranged, or excessive.

1. Deficient secretion is indicated either by scanty, hard, and dry stools, in which, though the bile is sufficient to give colour to the passages, its whole quantity is very small, or by an absence, more or less complete, of the bilious colouring matter. Several morbid conditions are connected with this state of the passages.

A slight degree of it may be attended simply with constipation. The bowels act sluggishly, because defectively supplied with the bile, which is one of their normal stimulants. in a higher degree, it induces a condition sometimes considered as a phase of dyspepsia, sometimes rather indefinitely called bilious disorder, which is marked by epigastric uneasiness, feelings of vague abdominal discomfort, often colicky pains, defective appetite, slight fur on the tongue, perhaps some sallowness of the face, and more or less mental inertness, depression of spirits, or even intellectual aberration. Jaundice is a still higher stage of the same disorder. in this affection, the secretion of bile has ceased, the stools are clay-coloured, and the yellow colouring matter of the bile, not escaping by the regular emunctory, accumulates in the blood, and is thrown off in the urine, upon the skin, and everywhere through the tissues. All the above disorders are grades of the same affection, which has its foundation in torpidity of the liver; and the remedy is to stimulate that organ to increased secretion. From two to eight grains of the blue mass, or from half a grain to two grains of calomel, given every day or every other day at bedtime, and followed next morning before breakfast by a gentle laxative, will very generally restore the proper colour to the passages, and remove the disorder. in the slightest cases, the cure is often effected by one or two repetitions of the smallest dose; in the severer and more lasting, it may be necessary to persevere with the larger doses for a long time, and even to call in the aid of other measures. A severe and obstinate attack of jaundice may, I believe, often be averted by directing attention to the stools in cases of slight digestive derangement, and, upon finding them deficient in colouring matter, resorting to the alterative mercurial treatment here pointed out.

In another set of complaints, instead of constipation there is looseness of the bowels; and the passages consist of liquid matters, sometimes but slightly tinged with bile, sometimes wholly destitute of it, and resembling oatmeal gruel in appearance. Hence arises a not unfrequent variety of diarrhoea; and I have occasionally seen our endemic cholera take on the same character; the discharges being nearly colourless. Under these circumstances, either from torpor of the liver, or active congestion of the organ interfering with its function, the portal blood is not carried through it with the ordinary rapidity, and consequently accumulates in the blood-vessels of the stomach and bowels, which relieve themselves by excessive secretion of serous or muco-serous liquid. The evacuations are sometimes so copious from this cause as to involve life in danger. in a higher state of the congestion, or a peculiar condition of the blood, the vessels relieve themselves by a sort of hemorrhagic exaltation; the blood oozing from extensive portions of the surface, and mixing intimately with the mucus, so as to produce copious black, tar-like passages. This is melaena. All these conditions, the diarrhoea, namely, the cholera, and the melaena, may be happily treated by the alterative use of mercury, in a manner somewhat different from that above recommended. From the irritable state of the alimentary canal, the doses suitable in constipation might endanger an increase of the irritation. Very small doses frequently repeated, and combined with small doses of opium, are now indicated. One-sixth of a grain of calomel with one-eighth of a grain of opium, may be given every half hour, hour, or two hours, according to the urgency of the case; and, if a speedy checking of the discharge be deemed essential, a grain of acetate of lead may be added to each dose. These doses should be continued until some impression is made on the disease, and then given at gradually lengthening intervals, until it ceases; care being taken not to push the medicine so far as to cause salivation. Sometimes it will be found useful to give the mercurial on this plan only every other day, leaving the patient without medicine, or at least without the mercurial on the intervening day.

In cholera infantum, and the diarrhoea of young children, deficient secretion of bile is an exceedingly common element, and calls for the same treatment. in these cases, the dose of calomel may often be reduced with propriety to one-twelfth of a grain, or even less, every hour, especially when there is vomiting at the same time with purging. Not unfrequently there is excess of acid in the primae viae, evinced either by the sour smell, or greenish colour of the intestinal discharges. Here the blue pill or mercury with chalk may be substituted for the calomel; the former being associated with prepared chalk or oyster shell, in cretaceous mixtures. One-quarter of a grain of the blue pill, or a grain of the mercury with chalk, may be given every hour or two, until bile is sufficiently restored to the passages. in order to make a more rapid impression, the late Dr. Physick was in the habit of treating the bowel complaints of children, over two years of age, with much larger doses of calomel, giving two grains every two hours until the disease was checked. I have occasionally imitated the practice, with the effect of promptly arresting the discharges; but the doses should not be repeated more than three or four times, on any one occasion.