The selection of an iodide for internal administration is influenced by the type of the individual, by the condition of the heart, and by the purpose to be subserved. If an idiosyncrasy to the action of an iodide exist, its nature and power should be ascertained. When the combinations of iodine with alkaline bases can not be taken, iodide of starch—" amylum iodatum"—may be substituted, and, although not so efficient as a remedy, is far less likely to cause acute iodism, or to set up a gastric catarrh. Also, as the salts of potassium have a more depressing effect on the heart than the corresponding sodium salts, the latter are preferable when long-continued administration is required. On the other hand, if the circulation is active and the forces unabated, iodide of potassium will prove more effective.

The vomiting of pregnancy can sometimes be greatly relieved by drop-doses, every hour or two, of the tincture of iodine. This, like all other remedies for this disorder, is very uncertain, and precise indications for its use have not hitherto been ascertained. Catarrh of the duodenum, catarrh of the biliary ducts, and the jaundice dependent thereon, are, after the acuter symptoms have subsided, greatly benefited by the smaller doses of iodide of sodium or ammonium. This is one of the best remedies for the first stage of cirrhosis. The efficacy of the iodide is increased by combination with arsenic: Rx Ammonii iodid., 3 j; liq. potassii arsenitis, 3 ss; tinct. colombae, oz ss; aquae, oz jss M. Sig.: A teaspoonful three times a day, before meals.

The preparations of iodine and the iodides are, generally speaking, contraindicated in all inflammatory states of the intestinal canal; but in passive hemorrhage, and diarrhoea from atony of the mucous membrane, the tincture or compound solution of iodine in small doses—one or two drops—frequently repeated, renders important service (Schmidt).

Large doses (grs. xv 3 ss) of the iodide of potassium, three or four times a day, often afford remarkable relief in aneurism, and sometimes effect a cure. The author has seen several instances in which great benefit was derived from it, and one case certainly in which a cure apparently resulted. He is, therefore, able to confirm the observations of Chuckerbutty, Roberts, Balfour, and others.

In arteriosclerosis and in sclerosis of the heart, kidneys, and other organs, our French colleagues maintain that the iodides possess distinct curative power, if given in sufficient quantity, for several years. About one drachm daily is the minimum amount that will accomplish the object. As, however, the potash base is more injurious in action than the soda base, the iodide of sodium should be preferred for this purpose. Prof. Sée, Heuchard, and others of the French school, are convinced that the condition of sclerosis, which, as it affects the arterial system, plays an important part in pathogeny, can be arrested, the morbid deposits removed, and the integrity of the vessels restored. Pro- longed use of the iodide of sodium, although not without its disadvantages, can be safely carried on if occasional intermissions are allowed.

In summer catarrh or hay-asthma, the best results are obtained by the use of larger doses, and the efficacy of the iodides is increased by combination with arsenic: Rx Potassii iodidi, oz j ; liq. potassii arsenitis, 3 j ; aquae, oz iv. M. Sig.: A teaspoonful every four or six hours. With the internal use of the iodides may be combined the local use, to nares and fauces, of the following solution: Rx Tinct. iodinii, 3 j ; acid. carbol., gtts. x; aquae destil., oz iv. M. Sig.: Apply with a postnasal syringe. Ethyl iodide is especially valuable inhaled frequently.

The iodide of potassium is one of the most effective remedies which we possess for spasmodic asthma. But it is not adapted to all cases arising under various conditions—a fact which explains the difference of opinion on the subject between Williams, Salter, and others. It is most beneficial when the asthmatic seizures are reflex. Salter, however, holds that we possess no exact indications for its use, and that cases the most diverse are sometimes benefited in a remarkable manner.

Chronic bronchitis, with profuse secretions (bronchorrhoea), is frequently improved by the iodides, more especially the iodide of ammonium. The efficacy of this remedy is increased by the conjoined administration of arsenic. In capillary bronchitis, the author has witnessed most astonishing relief by the rapid administration of iodide of ammonium in small doses. It may be combined with the carbonate, or with the stimulant expectorants. To remove the deposited inflammatory exudations of catarrhal and fibrinous pneumonia, no remedy is more efficient than the iodide of ammonium. To lessen the effect of this remedy on the tissue-changes, arsenic should be combined with it, and every means used to support the body nutrition. The iodide of potassium is one of the remedies resorted to in chronic pleurisy, to promote absorption of effusions. In these cases the iodides are administered steadily for a considerable period, and pilocarpine given, as may be necessary, to increase the sorbifacient action.

Affections of the broncho-pulmonary mucous membrane, alluded to above, in which there is profuse exudation, all inflammatory symptoms having subsided, are advantageously treated by iodine inhalations. The method which the author has found most convenient is the following: A small, wide-mouthed bottle, containing a moistened sponge, is placed in a vessel of hot water. The tincture of iodine (gtts. v—gtts. x) is dropped upon the sponge, and, as the vapor of iodine rises, is inhaled with the vapor of water. This inhalation is serviceable in acute catarrh, hay-asthma, and chronic bronchitis. The carbolate of iodine (tinct. iodi, 3 ij ; acid, carbol., 3 j) may be used instead of the simple tincture of iodine. Ten to twenty drops for inhalation.

But few affections of the brain, non-specific in origin, are benefited by the iodides. According to Niemeyer, the iodide of potassium given to iodism has in few instances cured basilar meningitis. The author, who has used it faithfully in various cases, has not been so successful. Trousseau et Pidoux express their disbelief in the reported cures of tubercular meningitis by this agent. Seguin maintains, on the other hand, that remarkably good results sometimes follow the use of large doses of the iodides in other than specific diseases—in the various subacute and chronic inflammatory affections of the meninges and brain.

No remedy is more efficient in the treatment of certain glandular enlargements of the thyroid, spleen, and lymphatic glands. Goitre is curable by the internal and external application of iodine, when it consists of simple hypertrophy of the gland-elements. Cystic and calcareous degeneration of the thyroid are unaffected by the use of iodine preparations never so vigorously used. One of the best remedies for true goitre, as will be seen hereafter, is the unguentum hydrarg. iodidi rubri. Enlarged spleen, when it consists merely of an hypertrophy of the organ (chronic splenitis), is cured by the internal use of the iodides conjoined with the local use of iodine-paint, or ointment of the red iodide of mercury. The enlargements of the spleen and liver, with functional derangement of these organs, which are caused by malarial disease, are most effectually removed by moderate doses, frequently repeated, of the iodide of ammonium. The author's experience jus- tifies him in strongly urging the combined use of iodide of ammonium and arsenic in chronic malarial poisoning.

The prolonged administration of the iodides has the power to retard the growth and to remove the changes which ensue in chronic Bright's disease (fibroid degeneration), and the arterio-sclerosis accompanying it.

The utility of the iodides is most conspicuous in certain constitutional states. The expectations which were at first entertained of the cure of scrofula by iodine and its preparations have not been realized. The iodides are unquestionably useful in the scrofulous (so called) enlargements of the lymphatic glands, but cod-liver oil and suitable hygienic means are more influential in improving the strumous diathesis. The preparations of iodine are effective only when simple hypertrophy of the lymphatic glands has taken place; if they have undergone caseation, or have proceeded to suppuration, no medicine has any influence over them.

The most important therapeutical applications of the preparations of iodine are in the treatment of constitutional syphilis. For the primary and secondary stage, mercury is generally admitted to be best; but for tertiary symptoms no remedy at all approaches the iodide of potassium. In the secondary affections of the skin, mercury, especially if it have not been given for the primary troubles, is to be preferred in the papular, tubercular, squamous, and pustular syphilides; iodide of potassium in the ulcerating, especially if the patient is cachectic. It may be stated in general that the preparations of iodine are indicated when the patient is under the mercurial cachexia. On the other hand, it is well known that sometimes, even when the tertiary symptoms have not been relieved by a thorough course of iodides, mercury will quickly remove them. But this fact does not invalidate the rule that the iodides are specially serviceable for the tertiary period.

No therapeutical fact is more conspicuous than the cure of syphiloma of the nervous system by iodides. Mental disorders, epileptiform seizures, paralytic states, etc., dependent on gummata, nodes, etc., are usually removed in a manner little short of magical. Neuralgia of the fifth (tic-douloureux), the pain being nocturnal chiefly, or nocturnal pain in the head, is similarly promptly cured. In syphilitic affections of the brain, more imperatively than in the same affections of other organs, are large doses of the iodide of potassium required. The limitation of the dose depends entirely on the physiological susceptibility of the patient, and the influence exerted over the progress of the case. Hence the dose may vary from ten grains to a drachm every four hours, or three or four times a day. The symptoms of iodism—the use of the agent to saturation—should be induced; for this effect is the only measure of the therapeutical power of the remedy. The more promptly iodism can be induced, the better, for the soft nervous tissue may be quickly and irreparably damaged by syphilitic deposits and new growths. Syphilitic paraplegia is equally amenable to the same means; but, as above remarked, much depends on the promptness with which the iodide is used.

Recent experience has conclusively shown the curative power of iodine in malarial fevers. Thus three hundred consecutive cases were, with few exceptions, promptly arrested (Anderson). In some cases no paroxysm occurred after the medicine was administered; sometimes the attacks persisted for two or three days, but then the relief was complete. The official compound tincture of iodine may be prescribed —for adults, ten to fifteen minims, three times a day, well diluted, and before meals. Carbolic acid, itself having considerable anti-periodic power, may be combined with the tincture of iodine. Rx Tinct. iodi, oz| ij; acid, carbolic, 3 ij. M. Sig.: Ten to fifteen minims three or four times a day. The tincture of iodine is stronger than the compound tincture. If quinine be necessary to break up the paroxysms, iodine is highly useful in the interim, as has been indicated. Some recent experiences by Dr. Atkinson, of Baltimore, throw doubts on the previous statements. He found that iodine failed in two thirds of the cases of intermittent fever.

The use of the compound solution of iodine during the course of the first and second week of typhoid fever is known in Germany as the "specific treatment." A very considerable reduction in mortality appears to have followed this method. The solution of iodine or the tincture is administered regularly three times a day, well diluted with water. When it does good, the temperature falls, the nausea lessens, and the diarrhoea is restrained within safe limits.

Chronic rheumatism, when there are present thickening of the fibrous tissues, and inflammatory depositions about joints, tendons, periosteum, and nerve-trunks, is often very signally benefited by the iodides. The cases in which these remedies prove so serviceable are most probably due to syphilitic, mercurial, saturnine, or other constitutional causes. There are, in our modern life, many ways in which these mineral poisons enter the organism, and it is probable that they are often undiscovered and even unsuspected causes of rheumatic symptoms. Lumbago, sciatica, and paraplegia, apparently of rheumatic origin, and curable by the iodides, may not unfrequently be caused by syphilis, mercury, copper, tin, or lead.

The various accidents caused by the metals above named, especially the mercurial and saturnine, are removed by the use of the iodides, notably by the iodide of potassium. With regard to the dose necessary, what is true of syphilis is equally true of the mineral poisons: in order to remove them, the organism must be saturated by the remedy. From fifteen grains to a drachm, three or four times a day, should be given; but the measure of the quantity required is the effect produced. The iodides penetrate into every tissue, convert the deposited metal into soluble combinations, and cause them to be discharged by the various organs of excretion, chiefly by the kidneys. It has been repeatedly asserted that salivation may be induced, and existing salivation increased, by the use of the iodides for the removal of mercurial salts from the organism; but the author has not witnessed any facts which support this statement.

In shin-diseases of syphilitic origin there can be no question as to the utility of the iodides. But these remedies are more especially curative in the tertiary affections, especially in destructive syphilitic ulcerations. Hebra insists, and with justice, that the preparations of iodine are only useful in lupus, whether syphilitic or scrofulous, and do not permanently improve other cutaneous diseases. Greve asserts that large doses of the iodides (Э j- 3 j ter die) rapidly cure psoriasis; and in this opinion specific origin is not said to be necessary to the curative result. Boeck confirms Greve's statements.