ELECTRICITY, MEDICAL USES OF. Three forms of electricity are used in medicine: Static, galvanic, and faradic.
Static electricity is obtained from a machine in which glass plates are rapidly revolved against chamois rubbers or horsehair brushes. The elec tricity is produced in a succession of sparks. which may be received in a Leyden jar, or in the body of a patient, insulated by being placed on a glass-footed chair. Static electricity has but little quantity, but an enormous eleetro-motive force; the current has high potential and high frequency but is devoid of appreciable electro lytic effects. Its use in medical practice is to modify and regulate funetional processes, includ ing secretion, excretion, sleep. respiration, eircula tion, and nutrition.
Galvanie electricity is obtained from a galvanic battery, composed of several cells connected in the usual way, the terminal wires being inserted into metal binding posts, to which electrodes are fastened. The elements used are zinc and carbon in most wet batteries, and the fluid in which they are immersed is it so lution of bichromate of potash containing sul phuric acid. and also a salt of mercury, that the zinc may be continuously amalgamated. A eurrent-eontroller, or switeh, is so arranged that one, two, three, or more cells may be used at a time, according to the strength of eurrent de sired. The electrodes. or terminals, whWh arc applied to the body, are composed of metal covered with sponge., and insulated so as to be grasped by the wooden handles by the physician without drawing off the current. The sponges are wet before applying. Galvanism causes a contraction of the muscle against which the elec trode is applied, on application and again on withdrawal. During the interval of applieation there is a sensation of heat (also of pain if the amperage be great) and of tingling. A sensation of light, a metallic taste, or a buzzing sound is experienced when the •urrent is passed through the retina, the tongue, or the ear respeetively. Galvanism is applicable in treating very many conditions and diseases of the nervous system, as well as of the greatest use in diagnosis of dis ease.
Faradism is (shined from a faradic battery. An important part of this apparatus is a small induction mil eonsisting of a core of short. straight. soft iron wires. of lame diameter. around which is coiled many feet of wire. Through the wire is run an electric current which when interrupted causes an induced current to Pow in a second and surrounding coil and turns the iroll core into an elect Pass ing through the coil to the spring-support of the vibrator. the current goes to the num point on the interrupter. and thence back to the cell. completing the circuit. But as the cur rent, in passim the coil, makes the iron core an electro-magnet, it furnishes the energy that attracts the hammer on the spring-support, which. drawn to the magnet, breaks the circuit in leaving the platinum point of the interrupter; the current then ceases, the iron core loses its magnetism. the spring ceases to be attracted to the iron core, and its tension causes it to return to its former position. in which it touches the platinum point of the interrupter again, and :gain the circuit is closed. Thus the circuit is made and broken With extreme rapidity and frequency. The secondary coil is insulated from the primary coil aml it-. terminals are connected with the electrodes. The rapid making and breaking of the current in the priniary produces an induced current in the secondary which can be regulated at will by the operator. This induced current is applied to the human body by means of elect rodes. as in the galvanic battery. The effects of
faradistn are wholly electrotonie. It is useful in mild cases of spinal and peripheral paralysis. Changes of circulation or of molecular state may be excited in central organs by reflex irrita tion produced by faradism. General faradism is beneficial in gout and rheumatism. myalgia (rimscular rheumatism), in widespread eczema. in constipation due to indigestion. in hypo chondria, hysteria, and neurasthenia. Local faradism is beneficial in but few cases which are not ameliorated in larger measure by galvanism. Faradism is useful in testing conditions of mus cles: but here, too, galvanism is of greater value. Speeial electrodes of various shapes are used in applying the current to different parts of the body. A that oval electrode, about 6 by 4 inches, is useful in application-. to the abdomen or spine; a small, pointed electrode, for singling out one muscle of a -mall area, or testing a nerve; a small oval bean-shaped electrode, fastened to a rubber-covered wire. for swallowing in order to electrify the interior of the stomach; an electrode -shaped like a knitting-needle. with all but a half Mel' of the tip insulated, for intrauterine use; a wire brush for special use with the faradic cur rent, etc. An interrupting electrode is so made 1 hat with the thumb of the hand that applies the electrode the circuit may he closed and opened at will for testing accurately. A special electrode is arranged for the insertion in its extremity of bib paper saturated with a ding in solution, which is carried into the skin. when a current is passed. using this as the cathode. This is (-ailed the kataphonic electrode. A galvanic battery is furnished with a device by which the current may be run in different directions by moving a switch, thus altering the polarity of an electrode without moving it. This is especially useful in testing for degeneration in a muscle. Normally the cathodal elo-ure contraction of It muscle is greater than the anodal elosure contraction. If degeneration has oeeurred in a nerve supplied to a muscle the anodal and cathodal closure con tractions may he equal. or the anodal may he greater than t he cathodal. Fa rad ie contractility is less in muscle supplied by It degenerated nerve than in one in a normal condition. Its ua-aus of the kata phonic electrode a medicine like iodide of potas sium may be used lot-ally in definite quantity, as in a glandular enlargement; or cocaine may be applied over the painful spot in a neuralgia or neuritis. or may be applied to the gum of a sen sitive tooth before tilling or extraction is ac complished.
Besides the use of elect•ization in several dis eases. as stated under their own titles, in para graphs on treatment, galvanization is of immense value in exercising paralyzed muscles. securing their nutrition. and preventing their atrophy until relief of the central condition has been ac complished or regeneration of nerves been secured. In surgery the electrolytic action of the galvanic eurrent is employed in destroying tumors; hyper trophied tissue, as in the nasal cavity; removing !nevi and birthmarks. or superfluous hair, etc. The galvanic current is also utilized in heating a cautery for searing a surface or area, to secure a cicatrix; for causing counter-irritation, etc., its utility over the ordinary or Pacquelin's cautery being largely due to the fact that it can be placed in position when cold, and instantly heated to the required degree by passing through it a current of known amperage. For further information. con sult Rockwell, Medical and Surgieal Uses of Electricity (New York, 1S96). See DENTISTRY.