Definition and Historical Development

By the term metallotherapy is meant a curative method in which metals are applied to the affected area.

The influence of the noble metals over the bodily functions has been believed in from the remotest times within the historical period, and this belief has been acted on by many influential persons down to nearly our own era. The action of magnetic iron contributed to this mystical notion. Then came the wonder-working Mesmer. To the action of magnets was added that mysterious force evoked by the agencies employed by the Mesmerists. From such elements a pretended method of cure was elaborated, and a great many charlatans throve on the profits of the "system." Probably the most sustained success in this department of popular notions was effected by Dr. Perkins, of Connecticut, who invented a combination of metals arranged in the form of a cylinder, about six inches in length and two inches in circumference, which he called a tractor. Provided with a suitable handle, the tractor was slowly passed over the affected area, and the morbid process was drawn out or dispersed. Perkins's tractors excited great interest in this country, and in England an immense enthusiasm. An institution—known as the Perkinian Institute—was established in London, and many of the nobility and gentry resorted to it to be cured by the application of the tractors. In a book published by the son, there may be found many certificates of cures thus effected. These results are the less surprising when interpreted by the aid of subsequent developments from metallotherapy. Mesmer, Perkins, Hahnemann, appeared nearly simultaneously, and the theories of these three apostles of new creeds were developed by the revolutionary spirit of the times, rather than by original study, and were not the products of a systematic application to the truths of such science as then existed.

Metallotherapy, as now understood, had its origin in the experiments of Dr. Burq, which were first announced in a note addressed to the Academy of Sciences, and subsequently embodied in his thesis for the medical doctorate in 1851. He stated that a plate of metal—a silver coin, for example—applied to the skin, may remove the paralyses of motility or of sensibility occurring in hysteria; that the same metal was not equally successful in all cases, and that idiosyncrasies exist, so that in respect to each individual there is a special metal, active and curative. In one subject it may be gold, in another silver, and in a third copper, which has the power to restore the lost motility or sensibility. Burq also maintained that the same metal taken internally, whether in the form of a natural mineral water or in a pharmaceutical preparation, produced the same result. In other words, when a piece of metal, a coin, selected according to the special sensibility of the subject, is applied to an hysterical patient having permanent hemianaesthesia, the return of the normal sensibility is effected in from ten to twenty minutes through a space of some extent, above and below the point of application. Numbness, tingling, and other disorders of sensation, dysaesthesia, etc., precede the return of sensibility to the anaesthetic area. The restoration of the sensibility proceeds from the point of application of the metal, and enlarges in all directions until the whole side returns to the normal. At the same time, an elevation of the temperature recognizable by the thermometer, and an increase of motor power as shown by the dynamometer, take place. These changes in the state of the sensory nerves are coincident with dilatation of the capillaries. The special senses undergo the same modifications. Sight, hearing, taste, and smell, are also in the condition of anaesthesia, and as the general sensibility is restored, these special organs return to their normal state.

Such, in brief, were the facts announced by M. Burq. A commission, with M. Charcot at its head, was appointed to investigate the phenomena of metallotherapy. Hitherto the statements in regard to the effects of metals had been received with positive incredulity; but the commission not only confirmed the accuracy of Burq's observations, but added some new facts. The first discovery made by them was the phenomenon of "transfer." By this term is meant a transference of functional powers. When the sensibility, the temperature, and the muscular power are restored to the side which had been anaesthetic, the other or normal side loses a part of its general and special sensibility. The commission also ascertained that when metals are applied for the relief of hemianesthesia due to old organic lesions of the nervous centers (such, for example, as cerebral hemiplegia), sensibility is restored also, but in a more durable manner. Thus, in a case of anaesthesia of ten years' duration, produced by a cerebral lesion, this symptom yielded to the application of gold. Other instances of the same character, and equally significant, were reported by the commission. These facts led Charcot to entertain the supposition that the effects produced by the application of the metals are really due to electrical action. It was ascertained, indeed, that electrical currents measurable by the galvanometer are caused by the contact of the metals, and, conversely, that electrical currents of corresponding strength induced the same results as the metals, including the phenomena of transfer. The intensity of the current varies with the metal. In the case of a patient impressionable to gold, a current of two to twelve degrees suffices to restore the sensibility and the muscular force, while in one sensitive to copper, a current of forty to fifty degrees is required to effect the same result (Petit).

As was above stated, when the metal to which the subject is found to be sensitive when applied locally, is given by the stomach, the same result is reached—that is, the anaesthesia is replaced by normal sensibility, the temperature rises to the natural level, and the muscular power is restored. The commission discovered the remarkable fact that if, after the normal is thus resumed, the metal is again applied, the original anaesthesia comes on. To this return anaesthesia Charcot has applied the term metallic anaesthesia. A feeble electric current applied under the same conditions produces, also, a return anaesthesia, which is called postelectric. When the metallic plates applied to the skin are composed of metals superimposed, the same results as those obtained by a single metal are not produced. Thus, if in a patient sensible to gold a piece of silver is laid on the gold, the effects proper to the latter do not follow. The results due to the application of gold may be rendered durable in some cases by superimposing a piece of silver. If, after the effects produced by the application of a metal to which the patient is sensitive, another metal is placed above the first, the results due to the former may be fixed or rendered permanent.

Notwithstanding the incredulity with which these observations on the action of metals were at first received, they have come to be generally accepted. Prof. Westphal, after a study of metallotherapy at Paris, made some investigations at Berlin, which, on the whole, were confirmatory. Charcot's observations were also sustained by the experiences of Thompson, Horrocks, and Wilks. An important contribution to the subject was made by Dr. Hughes Bennett, when he found that other substances besides metals caused the same results. In this experience we have an illustration of the old and well-known fact that discoveries are being constantly reproduced. When the Perkins excitement was at its acme, Dr. Haygarth, of Bath, announced that wooden cylinders made in imitation of the genuine tractors had the same curative effects. It is clear, however, as M. Vigouroux has well said, that not all substances have the same action. This fact has also been demonstrated by Dr. Hack Tuke, who, having caused the anaesthesia to disappear by the action of a metal, substituted a piece of carbon of similar size and appearance, but the effect did not follow.