Page:The American Cyclopædia (1879) Volume XI.djvu/347

 MEDICAL ELECTRICITY 335 platinum wire of different thicknesses, and of various forms and lengths, to meet the require- ments of different cases, are connected with portable conducting wires in such a manner as to admit of the most convenient applica- tion. In electro-therapeutics two forms of cur- rent are used : the direct battery current, and the induced, electro-magnetic, magneto-elec- tric, or faradic currents. (See ELECTRO-MAG- NETISM, and MAGNETO-ELECTRICITY.) When the direct current is employed, the operation is called simply galvanization ; when the induced or interrupted current is used, the process is called faradization. The direct current may be used of such strength and so applied as to produce decomposition of the fluids and solids of the parts to which it is applied, an opera- tion which has received the name of electro- lysis. Needles of various forms and sizes are employed as electrodes. They are inserted into the diseased parts, and the therapeuti- cal results are dependent in a great measure upon the fact that diseased parts are more readily destroyed by electrolytic action than sound parts. Batteries for electrolytic pur- poses should be coupled for intensity, as quan- tity arrangement produces too much heat, and has not sufficient intensity to overcome resis- tance. The general effects of electricity upon the various parts of the body are as follows : When a current from 12 or 16 Grove's ele- ments is passed through the brain, by placing one electrode upon some part of the cranium, which should be slightly moistened, and the other upon some other part of the body, as along the spinal column, or in the hands or under the feet, flashes of light appear on breaking the current, and a metallic taste is perceived. M. Erb has demonstrated that the skull offers no obstruction to the passage of the current. Galvanization of particular parts of the brain will excite contractions of the muscles. Matteucci showed that electric stimulation of the crura cerebri is followed by muscular contractions; but the most marked effects of electricity are upon the special senses. If a metallic plate connected with one electrode is placed upon the forehead and the other over the infra-orbital nerve, it will cause the sensation of a vivid flash of light. Galvanic stimulation of that part of the sym- pathetic system supplying the iris will pro- duce dilatation of the pupil. % The sense of hearing is also intensified, and favorable re- sults have been obtained by repeated applica- tions of the continuous current through the parts containing the different portions of the ear. The olfactory nerve is not affected by the induced or faradic current, but a moder- ately strong continuous current will produce a peculiar odor, which is not to be confounded with that of ozone, afforded by the friction machine. The sense of taste is easily affected by the galvanic current. A simple experiment consists in placing a plate of zinc beneath the tongue and a plate of a more negative metal, 543 VOL. xi. 22 as copper or silver, above it, and bringing the edges of the two together, when a flash of light and a metallic taste will be perceived. Electrization of the motor nerves results in a contraction of the muscles which are supplied by them, which occurs upon the closing of the circuit, ceasing when the current is broken. The effect is greatest when the negative elec- trode is applied to the nerve and the positive to the muscle. Hitter found that when the current was applied in the direction of the nerve its excitability was diminished, but in the other direction the irritability was in- creased. If the electrodes are applied to the surface of the body, a sense of warmth will be felt in the part. A strong current will pro- duce a sense of prickling or tingling, which may increase to a state of extreme pain. With the interrupted or faradic current, if the breaks are made slowly, the sensation will differ from that which occurs when they are very rapid ; and this will vary with the part operated upon, and with the variety of elec- trode employed. A moist sponge may occa- sion only a slight disturbance; but a bundle of pointed wires may create an intense sensa- tion. The amount and distributions of the nerves beneath the skin will also be followed by a difference of sensation. Remak holds that the nearer the nerves are to the brain the greater will be the excitability. The applica- tion of the continuous current for any great length of time will diminish sensibility. Fara- dization and static electricity have but little influence upon the sympathetic system of nerves ; but the continuous current from a battery of many couples may be passed through many parts of it. When the cervical portion is electrically insulated, dilatation followed by contraction of the pupils occurs, the pulsations of the heart are less frequent, and the tension of the arterial walls is diminished. That the vaso-motor system of nerves may be decided- ly affected appears from the fact that galva- nization excites the peristaltic action of the intestines, and greatly affects the calibre of the capillaries and larger blood vessels. The stomach and intestines and other abdominal organs are readily influenced by applying the electrodes at either side of the abdomen, or by applying one electrode over the abdomen and the other along the spinal column. The continuous current sent through the splanch- nic nerves increases the peristaltic move- ments of the intestines, while faradization diminishes them. The details of the practice of electro - therapeutics, especially from the fact that changes are liable to be made, are purposely omitted in this work. See " Elec- tricity in its Relations to Practical Medicine," by Dr. Moritz Meyer, translated and edited by W. A. Hammond, M. D. (New York, 1869) ; u A practical Treatise on the Medical and Sur- gical Uses of Electricity," by George M. Beard, M. D., and A. D. Rockwell, M. D. (New York, 1871) ; " Clinical Electro-Therapeutics," by Al-