It is but a few years since this most valuable medicine first became known to the profession. Dr. Coindet, of Geneva, in Switzerland, has inseparably associated his name with the medical history of iodine, by having been the first to employ and recommend it. Knowing from antecedent discovery that it existed in burnt sponge, and aware of the usefulness of that remedy in goitre, he was led to suppose that iodine might be the real curative agent, and accordingly gave it a trial in the disease, which, as every one knows, is very prevalent in that region. His success fully answered his expectations; and, in a paper communicated, July 25th, 1820, to the Society of Natural Sciences at Geneva, he made known his invaluable discovery. The efficiency of the remedy in goitre naturally led to its employment in other tumefactions, especially the scrofulous; and the favourable reports made of it rapidly diffused its reputation throughout the medical world. The names of Brera, Lugol, and Manson are also favourably connected with the early history of iodine, especially in its relation to scrofula. The medicine was now experimented with in every kind of disease, and under the most opposite circumstances, and the most extravagant estimate was made of its wonderful powers. Time, however, has had its usual effect of moderating enthusiasm; and, with the advantage of abundant experience, and a cooler judgment, we are at the present day better able, than a few years since, to determine its real value, and proper position in the Materia Medica.

By far the most useful applications of iodine are those connected with its alterative properties. it is not unfrequently used for its influence over the secretory functions, and often also exclusively for its local effect. Under these three heads may be embraced all its important uses.

A. Preparations Containing Free Iodine

Its efficiency in this respect is prominently displayed in the resolution of various tumefactions. in all chronic enlargements and indurations of inflammatory origin, or mere hypertrophies from excess of the nutritive function, whatever may be the special character of the inflammation, or the seat of the tumefaction, whether in the glands, the cellular or ligamentous tissue, the muscles, periosteum, or bones, much advantage may be expected from the resolvent properties of iodine; and in such cases, there is, on the whole, no one remedy which equals it in the universality of its applicability, not even mercury. To the cure of carcinomatous, tuberculous, or melanotic tumours, or other heterologous formations, or of the indurations resulting from cartilaginous or osseous degeneration, it is wholly inadequate, as indeed are all other known deobstruent remedies. it has appeared to me that its extraordinary efficiency, in the resolution of chronic tumefactions, may be best explained by the theory, already advanced, of its special influence in promoting the normal process of disintegration; of stimulating, in other words, those changes in the ultimate constituents of the tissues, which, after these tissues have run their course of service, effect their destruction and elimination, while new structure takes their place, in its turn to go through the same changes. it is generally admitted that the vital powers, in these abnormal formations, are less vigorous than in the healthy tissue, and less able to resist influences tending to their destruction. it is no violent assumption, therefore, to take for granted that their ultimate structure yields, more readily than the healthy, to the over-stimulation directed to it by the iodine; while, for the same reason, its powers of repair are more feeble. Consequently, while, in the healthy tissues, the more rapid disintegration may be supplied by an equally excited nutrition, and no change of bulk take place, the contrary is the case in the affections under consideration, which lose more than they gain, and thus return in the end to the normal state. in this view, iodine may act on them with equal efficiency, whether it is conveyed to the tumours through the circulation, or reaches them by an endosmotic penetration.

It is not, however, solely in tumefaction, that iodine proves useful. in disease of perverted action, in which an abnormal condition has been impressed upon the tissues, which prevents them from the due performance of their respective offices, and which shows itself in ulcerations, eruptions, pains, and disordered function of various kinds, the use of iodine is often followed by the most happy results. The change which it produces in the ultimate organic constituents of the tissues, causing the old to be broken up and disappear, carrying with them their abnormal tendencies, while new and healthy structure takes their place, is very probably the source of its efficiency.

A third condition, in which the alterative powers of iodine show themselves, is one in which noxious substances, particularly the metallic, may have been deposited in the tissues, and, remaining fixed there, either by their insolubility, or their affinity for the organic constituents of the tissues, keep up a constant irritation, and consequently continued evidences of morbid action. As before explained, in the articles on mercury and lead, iodine, or at least the alkaline iodides, probably act in these cases by forming soluble combinations with the foreign matter, and thus causing it to be carried off from the tissues in the current of the blood, and ultimately eliminated. For this very interesting view of the curative influence of iodine, in certain obstinate affections, the profession is mainly indebted to M. Melsens.

Having endeavoured to understand the modus operandi of iodine as a remedy, and thus to discover rational grounds for its use, we are next to consider the special diseases in which it has been found useful.

Goitre. There are few complaints in which iodine shows more extraordinary curative powers than in this. Tumours of large size, and the growth of years, will often begin to give way as soon as the system is under the influence of the remedy, and will proceed onward, in steady progress towards a cure, under its continued use. it certainly will not cure carcinoma of the thyroid gland, nor any one of those new formations or degenerations in which the normal structure has been displaced by the diseased; but in all cases of pure hypertrophy, or resulting from an obscure chronic irritation or sub-inflammation in the tissue, in other words, all cases of simple goitre, as distinguished from other special diseases which may be seated in that as well as in any other tissue, a cure may be reasonably hoped for. The cases of this disease which have most commonly fallen under my personal observation have been in young women; and these have almost invariably yielded to the preparations of iodine. The remedy should be employed both internally and topically; and I have myself preferred the iodide of potassium in both ways, giving it internally in solution, and applying it externally, in the form of ointment, two or three times daily. Not unfrequently the disease will yield to the external use of the remedy alone. Sometimes the tumour, instead of yielding immediately, seems to be stimulated into inflammation; swelling, and becoming somewhat painful. in such cases, the local application should be omitted for a time, and replaced by emollient cataplasms, until the swelling has subsided; or a few leeches may be applied; but, after the subsidence of the inflammatory symptoms, the remedy should be resumed.* i do not believe that iodine is at all competent to correct the scrofulous diathesis. By its careful use, so as rather to favour than to impair digestion, it may contribute with other measures, such as exercise in a pure air, wholesome and nourishing food, the use of cod-liver oil, etc., to improve the general health, and thus, in some degree, to act favourably in the disease; but unassisted, it has little power, and certainly no specific power over the morbid tendency. it is to the cure of the local affections, while other means are employed to amend the state of the system, that iodine should be specially addressed.