ELECTRICITY, MEDICAL. Electricity, in its application to medicine and surgery, is employed in the following forms: 1. Electrization, by electricity of high tension, as obtain ed by friction of glass in the common electrical machine; 2. Galvanization, by current elec tricity of quantity, as set in motion by the voltaic battery; and 3. Faradization, by induced or interrupted currents, produced by magneto-electric or electromagnetic induction coil machines.
Electrization.—Frictional electricity is now seldom employed in therapeutics, on account of the inconvenience experienced in the management and insulation of the glass or common electrical machines; vet the powerful stimulant and counter-irritative effect of sparks drawn from the affected parts is still recommended in paralytic affections, in chorea and other nervous diseases; and the succussion produced by shocks from the Leyden jar is undoubtedly the most effectual remedy in amenorrhoea.
Galvanization.—The effect of passing a voltaic current from a battery of many ele ments through the living body, is to cause a shock or contraction of the muscular tis sues, succeeded with a distinct interval by a momentary sensation or flow of heat due to the electric and nervous (?) polarization of the circuit. During the continued passage of the current, slight tingling sensations and elevation of temperature are observed, especially in those parts in contact with the electrodes or poles, which become painful and congested, and finally inflamed and ulcerated. On opening the circuit, the depolar ization of the tissues which ensues is accompanied by a second shock and subsequent glow of heat, which arc powerful in proportion to the length of time the circuit has remained closed. The amount of contraction in the muscle has relation to the intensity rather than the quantity of electricity passed through it—that is, to the rapidity with which the electric state is changed, rather than the amount of that change. The calorific effect of the current is proportionate to its quantity. Thus, a single pair of plates of platinum and zinc, an inch square (charged with chromic acid), will, under ordinary circum stances, exercise little or no physiological effect; but if the same pair be divided, so as to form a compound battery of twelve smaller pairs, its application will be attended with the shocks and calorific effects described. A furtherdivision into 24 or more pairs
increases the shock, but the sensation of heat becomes less marked. With certain limit ations, therefore, the shock of the battery depends on the number of its elements, with out regard to their size, its calorific effect to the area of its plates. The nerves of the organs of special sense, when subjected to galvanization, evidence phenomena pecul iar to their proper function. Thus, the passage of the current through the retina is attended by the sensation of a flash of light, which is bluish when the positive pole is applied to the eye, and tinged with the complementary orange when the force is trans mitted in the opposite direction.. A faint sensation of light is also perceived when the skin of the face or mucous membrane of the mouth is galvanized, caused by reflex action from the sentient filaments of the fifth pair of nerves which are distributed to those parts. Galvanization of the ear gives rise to bubbling, ringing, or cracking sounds, and occasionally to distinctly musical tones; that of the tongue, to an acid taste under the positive pole, and an alkaline taste under the opposite one; that of the lining mem brane of the nose, to sneezing and a peculiar smell, which differs with the direction of the current. The continuous gentle action of small single and compound voltaic arrange ments has been more or less successfully employed in paralysis, amaurosis, and neural gia, either by application to the surface of the body, or carried directly to the affected parts by needles thrust into them (galvano-puncture). More powerful batteries, con sisting of six or eight cells of the carbon battery of Bunsen, the nitric acid battery of Grove, or the platinized zinc battery of Strethill Wright, have been used to coagulate the fibrinous contents of aneurismal sacs—to decompose calculi in the bladder (?)—and to render platinum plates or wires incandescent, for the surgical cauterization of inter nal parts not otherwise easily accessible.