Effects

In a dose varying from five to twenty grains, calomel generally operates briskly as a cathartic, producing copious bilious stools, which, when the dose has been somewhat large, are usually of a dark-brown colour, often approaching to black, though yellow in thin layers, and of a peculiar characteristic odour. In smaller doses, the medicine vol. ii. - 36 acts as a laxative; and the stools, instead of being dark, are now, for the most part, of a bright bilious yellow. in some instances, especially in children, they are green. it is not difficult to explain these different appearances. When the bile is eliminated in moderate excess, by small doses of the medicine, it has its normal colour of yellow. When produced in great excess, under a powerful stimulus to the liver, it is dark-brown, in consequence of the concentration of its colouring matter, but becomes yellow if diluted, or viewed in thin layers by transmitted light. if it meet with an acid in the bowels, it is rendered green, and this is particularly apt to be the case in children.

The purgative action of calomel is usually slow. if taken at bedtime, it will frequently not operate until morning; and generally from five to eight hours elapse before any decided effect is experienced. in most cases, its operation is sufficiently easy, with little or no inconvenience to the patient; but frequently a little nausea and griping pain are felt, about the time that purgation commences, or a little before. it very rarely produces any immediate evidence of irritation of stomach.

But, though thus efficient and generally moderate, it is, in a relatively few instances, very much otherwise. I do not now refer to those cases in which the medicine may be impure from contamination with corrosive sublimate, or may be administered with substances calculated to render it poisonous, as muriate of ammonia or nitromuriatic acid. Given in this manner, it may be violently irritant in any case. But the instances I now have in view are those in which the medicine is given in its perfectly normal state, and without improper accompaniment. This violent action of calomel is confined to a comparatively few individuals, and is connected with constitutional peculiarity or idiosyncrasy, as it is the same with them under all circumstances. These persons have constitutionally a strong susceptibility to the purgative action of the medicine. The dose which, in most persons, operates kindly, occasions in them vomiting and purging of bile, with excessive nausea, and severe spasmodic pain in the stomach and bowels; in fact, a complete attack of cholera morbus, which, however, so far as I have observed, always subsides in a few hours, or may be checked by the administration of an opiate. in these same individuals, a small dose, as a grain, or even half a grain, will operate once or more on the bowels, producing bright bilious discharges, and with no great inconvenience, but still some griping pain, and feelings of nausea or sinking in the epigastrium. This peculiar susceptibility I have known to be hereditary. in all these cases, the unpleasant effects are not produced for several hours, proving that they are not the result of a direct irritant action of the calomel on the gastric mucous membrane, but arise probably from the bile thrown out into the duodenum.

A peculiarity of the purgative operation of calomel is, that it is not increased by an increase of the dose after a certain point. Up to that point, it obeys the general law of acting in proportion to its dose; but, when the quantity has been ascertained capable of producing the full cathartic effect, it may be almost indefinitely increased, without any or with very little increase of the discharges; and, indeed, the effect is sometimes lessened. it will be seen, when we come to the consideration of the mode in which calomel acts as a purge, that this peculiarity can be satisfactorily explained.

Another interesting point is that neither this, nor any other preparation of mercury, is disposed to operate specially on the bowels when admitted into the system through the outer surface.

Occasionally, when taken as a purgative, calomel will salivate. This is not apt to happen when it operates well upon the bowels, and, therefore, occurs less frequently from large than small doses. But there are individuals peculiarly susceptible to the constitutional influence of mercury, who are always salivated by calomel in purgative doses, whether given alone or in combination with other cathartics. One of the worst cases of ptyalism I ever witnessed was produced by eight grains, given as a purge to a female affected with erysipelas. For such persons mercurials should be prescribed with great caution, and in very small doses.

Children require much larger doses of calomel as a purgative, pro-portionably, than adults. A quantity which will generally operate readily on a grown person, will often scarcely act on a child two years old, unless aided by other cathartics. Generally speaking, calomel acts mildly, though effectually, on children. in a very few instances, when it has failed to purge, I have known it to produce a slight ptyalism in infants; but this is extremely rare. in two or three cases, it has seemed to me to be the cause of ulcers in the mouth, in children from one to three years old, when due caution was not observed to secure a purgative effect by the subsequent administration of castor oil; but the ulcers healed without difficulty, and no evil resulted. As to the fears entertained of deformity of the limbs, spinal disease, white swellings, etc., I believe they are quite chimerical. it is highly probable that these affections have occurred in children to whom a dose of calomel had once been given; but they might as justly be ascribed to a dose of magnesia, or rhubarb, or castor oil, or even more justly to the milk of the mother, which the child takes every day. Out of hundreds of infantile cases, in which I have seen calomel purges administered, I have in no one instance known of any permanent injury.