This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
For the sight, galvanism is preferable to electricity by induction, as it is more powerfully stimulant to the organ of vision.* If either of the inductive machines be used, the electro-mag-netic with a double wire should be preferred, as the more energetic of the two. The application may be made carefully to the ball, and around the orbit.
* Dr. Julius Althaus, of London, who is high authority on electrical subjects, states that a very feeble galvanic current applied to the face, such as may be excited by the contact of a silver and copper coin, is sufficient to cause a flash of light; while, if a number of large plates are used, as in Grove's or Daniell's battery, the influence on the retina is so great, that instantaneous blindness might result. The effect is greater when the current is directed to the mucous membrane, whether of the eye, the nostril, or the mouth, than to the skin, and greater when to the skin previously moistened than dry. But, though thus energetic in its action on the organ of vision, the continuous or galvanic current exerts little influence over the muscles of the face, which are powerfully acted on by faradism or the interrupted current, while the latter has little action on the eye. Hence the great importance of a proper discrimination in the application of the different currents to affections of the face. For deficiency in the nervous power of the retina, galvanism would be the remedy; in palsy of the muscles, faradisation; and if, in the latter case, galvanism should be employed, it would not only do no good to the muscles, but might seriously disturb the healthy vision. (Med. T. and Gaz., Aug. 1862, p. 219.) - Note to the third edition.
In operating on the ear, the external meatus should be half filled with warm water, and a metallic wire from one of the poles should be introduced into the liquid, while the other excitor is applied to the nape of the neck; or the second excitor, protected by caoutchouc, except at the end, may be introduced through the nostrils, so as to come into contact with the Eustachian tube. As the tympanum, however, is very sensitive, great caution must be observed.
When the electric influence is wanted in the organ of smell, a small sound, protected as usual except at the extremity, may be passed over the Schneiderian membrane; when in that of taste, the same instrument may be passed over the sides of the tongue and the palate; the second excitor, in both cases, being applied to the back of the neck.
The testicle being very sensitive, must be operated on with caution; two excitors being placed near each other upon the scrotum. For operating on the vesiculae seminales, one excitor may be introduced into the rectum, and the second into the bladder, if there be no contraindication; otherwise the latter may be applied on the external surface. In insensibility of these organs generally, the influence should be directed along the whole course of the urethra, as well as to the different parts externally.
Notwithstanding the localization effected by these methods, a secondary influence will sometimes be extended to the nervous centres, against which it is necessary that the operator should be on his guard. The pain itself produced in the part necessarily affects the cerebral centres; and, when care is taken to limit the current by keeping the poles near together, this is the chief, if not exclusive source of general disturbance that may be apprehended. In cases of paralysis of sensation, as well as motion, none of this effect is experienced. The muscle may contract; but, however long the operation may be continued, the patient is sensible of no inconvenience. Even reflex action from the spinal centres is excited by this localized contraction only in certain pathological conditions. But when there is no loss of sensibility, much care is necessary. Certain individuals are, from idiosyncrasy, so exceedingly susceptible, that a slight influence, even insufficient to cause local sensation, occasions faintness, giddiness, dimness of vision, nausea, vomiting, and general feelings of torpor or numbness. These persons are unfit subjects for the use of the remedy. The pain occasioned by the interrupted current has been employed successfully in overcoming the obstinacy often exhibited in feigned diseases. Under the impression that the electricity is employed as a remedial agent, the malingerer, unwilling longer to submit to the pain, acknowledges himself cured by the remedy. (Dr. Addinel Hewson, Am. J. of Med. Sci., Jan. 1861, p. 111).
In 1825, M. Sarlandiere proposed the direct application of the electric influence to deep seated parts by means of acupuncture; and, seconded as the measure was by the recommendation of Magendie, it acquired for a time great reputation, and was extensively resorted to. It consisted in introducing very sharp needles through the skin into the part or organ which it was desired to excite, particularly the muscles, and passing the current through them, so that in proceeding from point to point of the needles it must necessarily traverse the part. But the results have not corresponded with the first sanguine expectations, and the measure is at present seldom resorted to. Nor is it now necessary in medical practice; as the methods of M. Duchenne accomplish the same end more effectually and less disagreeably. The objections urged by M. Duchenne against it are, 1. that the electrization of the muscle cannot be separated from that of the skin; 2. that the cutaneous excitement being confined to the course of the needle, surfaces of considerable extent could not be stimulated; 3. that the contractions caused by it are irregular and cannot be foreseen; 4. that to excite the whole of a muscle, especially a large one, so many needles must be introduced that few patients would be found willing to bear the pain; and 5. that, if it be desired to excite the muscle by passing the needle through the nerve, the operation is almost always impracticable. Nevertheless, acupuncture may sometimes be usefully employed by surgeons for the discussion of tumours, and for promoting the coagulation of the blood in a neurisms. Platinum, or gold needles, should be used preferably to steel; as the latter may become oxidized, and thus irritate the parts. When a galvanic battery is used, the parts penetrated by the needle are apt to become inflamed, and a caustic effect is not infrequently produced.
Great importance has been attached to the transmission of the electric current along the nerve, and in one direction rather than another, in imitation of the course of nervous influence. But much of what has been said on these points has been purely theoretical. M. Duchenne has come to the following conclusions. 1. In man, whatever may be the direction of the currents, or the degree of vitality of the nerves they traverse, the same results are always produced, when the conductors are applied to any portion of the course of the nerves; namely, muscular contractions and sensations. 2. A current prolonged for a considerable time along a healthy nerve, whether it be continuous, or interrupted with rather short intermissions, weakens neither the contractions, the sensations, nor the voluntary movements, and produces no reflex phenomenon above the point excited. 3. A current long protracted in a nerve considerably debilitated, notably lessens its excitability, but without influencing the voluntary motions. 4 Changes in the direction of the current exercise no appreciable influence over the muscular contractility or sensibility in man. 5. Electrization of the terminal nerves of a limb produces sensations only in the points excited. 6. The currents which pass from the nervous extremities to the nervous centres, act principally on the sensibility of the limb, and produce, above the point excited, contractions which are irregular, and little proportionate to the intensity of the sensations. 7. Finally, the mode of electrization, by reflex action, has little efficacy in the treatment of palsy, and sometimes causes persistent neuralgia in the excited limb. (Duchenne, pp. 99, 100.) Should there be cerebral lesion existing at the time, it might do serious mischief. (Ibid., p. 97.) A fact worthy of recollection is, that electric excitation of the surface is more effective in bringing on reflex muscular contraction, than excitation of the muscles themselves. (Ibid., p. 33).