SIXTH SECTION.

METHODS OF USING INTERRUPTED AND CONSTANT CURRENTS.

Duchenne, De l'Électrisation localisée, 2e édit., 1861 (l. c., pp. 47-102). Rich ters Bericht über die electro-physiologischen Arbeiten des Dr. Duchenne de Boulogne (in Schmidt's Jahrbüchern, Band lxxx., p. 258, et seq.). Dr. B. A. Erdmann, Die örtliche Anwendung der Electricität in Bezug auf Physiologie, Pathologie und Therapie, Leipzig, 1860, pp. 70-164. R. Remak, Ueber methodische Electrisirung gelähmter Muskeln, Berlin, 1856. Dr. H. Ziemssen, Die Electricität in der Medicin, 3. Aufl., Berlin, 1866. Prof. A. Fick, Einige Bemerkungen über die neuere Electrotherapie vom physikalisch-physiologischen Standpunkte, in der Wiener Medic. Wochenschrift, 1856, Nos. 48 und 49. Prof. A. Fick, Die medicinische Physik, Braunschweig, 1856, p. 454, et seq. J. Rosenthal, Physikalische und physiologische Bemerkungen über Electrotherapie, in der Deutschen Klinik, 1858, Nos. 3 und 4. J. Rosenthal, Electricitätslehre für Mediciner, Berlin, 1862, p. 158, et seq. Brenner, Versuche zur Begründung einer rationellen Methode in der Electrotherapie, genannt: die polare Methode (Petersb. Med. Zeitschrift, 1862, Band iii., p. 257, et seq.).

THOUGH We have for a long time endeavored to direct the electrical current, for therapeutical purposes, into certain diseased organs, parts of organs, or tissues, and to avoid the neighboring parts as much as possible; though we have succeeded, for instance, in electrizing individual muscles, in conducting the electrical current into the bladder, etc., and have further, in order to avoid the burning of the skin, covered the excitors with soft moist leather, and, on the contrary, when we wished to irritate the skin, have placed the metallic plate on its dry surface-yet, to Duchenne is due

the honor of having systematically introduced local galvanization or faradization, of having extended it, and of having given to it technical terms. It was reserved for German science and thoroughness, scientifically to maintain and establish what French practical tact without understanding had discovered.

Duchenne based his method on the following observations: 1. If we place two dry electrodes on a dry, hard skin, there appear, at the points of contact, sparks accompanied with a peculiar crackling. 2. If in such a case we moisten one electrode, a superficial sensation is perceived at the point which is in communication with the dry electrode. 3. If we moisten a little the skin, the epidermis of which is thick, under both electrodes, there follows a strong superficial sensation, but no sparks nor crackling. 4. If both skin and electrodes are considerably moistened, neither sparks, crackling, nor burning are perceived at the points of contact, but phenomena of contraction connected with a corresponding sensation.

We are thus able to allow the electrical current to act only on the skin or on the tissues lying under it. Duchenne discovered that the first-mentioned phenomena-sparks, crackling, and burning-are the result of irritating the skin alone, and that the last mentioned-the contractions and the accompanying sensation-are the result of the irritation of the muscles or nerves alone. Two pathological cases led him to these conclusions. He placed the dry electrodes on the exposed crureus muscle of a wounded person: there followed contraction, accompanied with a peculiar constricting sensation; the dry electrodes laid on a muscle covered with uninjured skin produced a sensation of burning, but no muscular contractions; the electrodes (covered with moist sponges) now placed on the same part of the skin induced again muscular contractions, with their accompanying sensation. A second wounded person had the radial nerve at the lower part of the forearm destroyed, and there followed loss of electrical

contractility and sensibility in the muscles of the posterior part of the forearm, while the sensibility of the skin, its nerves not being injured, remained fully normal. In this case dry electrodes placed on different parts of the forearm always produced an intense burning, while moist sponges on the back part of the forearm excited neither contraction, nor the usually accompanying sensation.

In order to irritate the skin, Duchenne uses three different methods: 1, the electrical hand; 2, entire metallic electrodes; 3, metallic threads. In the first method, which is used only for the face, and in exceedingly irritable patients for other parts of the body, the physician places one moist sponge, connected with a polar wire, on a tolerably sensitive. part of the patient, for instance on the sacro-lumbar region or on the sternum, and taking the other electrode in his hand passes his fingers slowly over the perfectly dry affected part of the skin. In order to irritate the skin or other parts of the body, entire metallic electrodes are used, and carried backward and forward over the dry, or, when it is very hard, somewhat moistened epidermis. If we wish to excite powerfully a small circumscribed spot, we hold on it for a long time the point of an olive-formed or round electrode. The metallic brush, with which we either strike the skin (electrical scourging), or act on the same spot as long as the patient can endure it (electrical moxa), we use for irritating the surfaces of the hands, the soles of the feet, and in very sensible parts of the skin, by drawing it over the surface. Later we will consider the special diseases, in which the electrical irritation of the skin is serviceable here we will only remark, that the local effect at most remains local, and that we must consequently, when we wish to excite a considerable extent of the surface of the skin, subject it in all its parts to this treatment. In those points which, in the normal condition, possess a high degree of sensitiveness, it is well to begin with mild action, gradually increasing it, and as soon as a distinct sensation is pro

duced (especially in the face) to return to the less irritating method.

In order to excite the motor nerves or the muscles, we place the moist electrodes as near to one another as possible on the parts of the skin immediately over these organs. As to the reason for this, we must first remark that the extent of local galvanization cannot be so well indicated as if the muscle or tissue were immediately in contact with the conductors, and were alone acted on by the electrical current. The current here directed from without to any part of the body is most intense at its points of entrance and exit, yet it nevertheless spreads itself throughout the whole body. "Not only does the current," says Du Bois-Reymond," "pass through every molecule and part of a muscle, but also in its natural position through the bones, nerves, vessels, tendons, etc., in contact with it when the thigh is bent upon the abdomen, the lower leg on the thigh, the current passes through each molecule of an abdominal or thigh muscle over the entire foot, lower leg, thigh, abdomen with all its viscera, and, if the leg is placed in water, or is brought in connection with a conducting arch, into the water or the conducting wire."

If Du Bois-Reymond could announce in its generality this proposition in regard to the current of the animal body which is appreciable only through a powerful multiplicator, how much more valid is it where palpable currents from without enter the body! Here the current spreads itself between its in- and out-going points in all directions and through all open paths. But the intensity of the current is not equal in all parts. This depends on different circumstances. 1. On the length of the way between the point of entrance and the point of exit. As the strength of the electrical current decreases according to the length of an intercalated metallic wire, so is its intensity lessened according to the distance between the poles; consequently, when the

1 L. c., Bd. i., p. 687.

metallic conductors are placed on the dry skin one inch apart, they produce a much more powerful sensation than when they are applied at a distance of a foot from one another. 2. The current is strongest in the direct line which is the shortest distance between the conductors; its intensity decreases with the length of the curved way which we conceive to lie between the points of entrance and exit. Let us take an example, which Fick' has given and illustrated by a diagram, and lay one moist electrode on the top of the shoulder and the other on the forearm; all the curves, which the current, in order to reach from one point to another, can pass over, are of tolerably equal lengths, and consequently of tolerably equal resistance; the electricity in this case will distribute itself tolerably equally over the whole arm, and, moreover, when a not very strong current is used, the density will not be at any point so great as to excite muscular action. Had we, on the contrary, laid the two moist conductors near one another on the M. deltoideus, the ways, which the current could pass over, in order to go from one conductor to another, would be quite different as to their length, and the intensities of the current in the various curves would correspondingly differ: even with a weak current the intensity in the direct line between the conductors would be sufficient to produce a strong contraction of the deltoideus, while no disturbance of the neighboring muscles, the biceps and pectoralis, would be visible. Apparent exceptions to this law are found in the physics of the nerves-when, for instance, we excite a part of the N. ischiadicus, there follows a clonic or tonic spasm of the whole leg even to the point of the foot, and all the muscles supplied from the N. ischiadicus become contracted; contraction of the uterus, when one electrode is laid on the vaginal portion and the other on the foot, is to be attributed to the reflex action of the nerves of the neck of the womb, etc. 3. With different conductors the strength of the current is directly as 1 L. c., 457.