i shall treat first of the effects of iodine and its preparations on the system, and of their therapeutic uses, and afterwards of the different forms in which the medicine is administered. in the outset, it may be proper to say that, as iodine, after entering the circulation, always probably exists in a state of saline combination, it is not the element itself to which the effects are immediately attributable, but its salts; and hence the identity of the general influence exerted by its different preparations.

1. Effects Upon The System

The local effects of iodine and its preparations are more or less irritant, and, in this respect, the elementary substance is more energetic than most of its compounds. When iodine in solution is applied to the skin, it causes a deep orange-yellow or brown discoloration, which, however, often disappears without desquamation, either through the slow evaporation of the medicine, or the agency of emollient or demulcent substances. This would seem to show, that it is rather a mere imbibition than chemical combination which takes place; yet, if the application is made very freely, the epidermis seems to be chemically altered, and, under such circumstances, always exfoliates. inflammation, and, in the highest degree of its action, even a corrosive or escharotic effect, may result from the local use of iodine, especially when in contact with the mucous membranes. Most commonly, when ulceration or sphacelus has occurred, it has probably been the result of a dynamic operation, causing the death of the part through an over-exaltation of its actions; but it is not impossible that, in consequence of the strong affinity of iodine for hydrogen, it may sometimes abstract it from the tissues with a disorganizing effect. The irritant effect of iodine may result from its application in any form, whether solid, liquid, or aeriform, especially to the mucous surfaces.

iodine often exercises a most happy influence in the cure of disease, in doses which produce no other evident sign of their operation, and which are insufficient to disturb health in any discoverable degree. it is, therefore, eminently an alterative medicine.

Given in such quantities as to make its action sensible, it not unfrequently at first somewhat increases the appetite; but this is an effect which it produces in common with most other irritants, and which, if the dose is increased, passes into positive irritation, as evinced by gastric uneasiness, nausea, and some disturbance of the bowels, with or without colicky pains. A very common result of its continued use, even when no obvious irritation of stomach is produced, is soreness of throat, or some degree of inflammation of the air-passages. This may, indeed, be considered as one of the best practical signs of its operation on the system, and, when exhibited, should lead to a temporary suspension of the medicine, or a diminution of the dose. Some degree of headache, or frontal uneasiness, is also not a very uncommon symptom. When the system comes fully and obviously under its influence, the pulse becomes more frequent, the warmth of skin is increased, the stomach is disturbed, the tongue furred, the head often uneasy; in short, a moderate febrile state is produced, which springs from the simply irritant influence of the medicine, not only in the primae viae, but on the system at large through the circulation.

Even under a less degree of its action than is required to produce this febrile state, it exhibits a disposition to increase the secretions. Perhaps there is no one of the secretory functions which is not occasionally stimulated, and yet no one so steadily and prominently, that the medicine can be said to have any special predilection. The skin, the mucous surfaces, the kidneys, the liver, and the salivary glands are more or less excited, one or another, or more than one, probably according to incidental circumstances which may give the medicine some preferable direction. Almost all writers agree in the statement, that the menstrual function also is stimulated. Occasionally, though rarely, profuse salivation has been noticed. in some instances, an effect has been produced on the mouth similar to the mercurial; but there is every reason to suspect that, in these cases, it was really an effect of mercury, liberated through . the influence of the preparation of iodine from an inert condition, in which it had for a longer or shorter time remained in the tissues.

The medicine is said sometimes to produce peculiar effects on the skin. Thus, an embrowned state of the surface, which has in one or more instances followed its use, has been ascribed to it as the cause. But the justice of this ascription may be doubted, when we consider how rare has been the coincidence, and yet how frequently such discolorations have occurred, without any known connection with iodine in any way. What is more certain is, that the medicine occasionally gives rise to eruptions on the surface, erythematous, papulous, eczematous, or impetiginous, which, however, have nothing serious in them, and yield readily on its suspension. iodine produces this effect in common with many other irritants of the alimentary mucous membrane, and of the general system, as copaiba and the turpentines; and there is nothing specific or peculiar in the result. Nor is it common. I have very rarely seen it, though very frequently prescribing iodine to hospital patients.

Absorption is said also to be promoted by iodine; and, in proof of this opinion, the facts are advanced that, when long continued, it produces general emaciation, and sometimes shows a disposition especially to attack the mammae and testicles, and to cause atrophy of these glands. But, in reference to the emaciation, this, I believe, is never induced by the insensible operation of the medicine, and, when it occurs, can readily be explained by the impaired digestion, and otherwise disordered state of the system, resulting from its irritating influence. As to the devastation which it was at one time supposed to produce in the glands specially referred to; this has come to be regarded as one of the apocryphal facts of medicine. So many thousand physicians have now been prescribing iodine for so long a time, and such multitudes of patients have been kept under its influence for months, and perhaps years, without any accident of this kind having been observed, that there is every reason to believe that the instances, which really have occurred of this apparent effect, were in fact simply coincidences. The mamma and the testicle are well known occasionally to wither, under other influences; and, if iodine had any special power of promoting this tendency, the fact would by this time have been established beyond doubt. instead of this general and partial wasting, which, in the earlier history of iodine, were bugbears to the profession, nothing is more common at present than to see our patients enjoying good general health under its prolonged use; and even increase of weight is not uncommon. The old idea, therefore, that iodine specially promotes absorption, must, I think, be abandoned.