ELECTRICITY. 763 ELECTRIC LIGHTING. Aviien interrupted causes an induced current to How in a second and surrounding coil and tunis the iron cure into an electro inajjnet. Pass- inj; through the coil to the spring-support of the vibrator, the current goes thence to the plati- num point on the interrupter, and thence back to the cell, completing the circuit. But as the cur- rent, in passing through 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 interrui)ter; 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 again the circuit is closed. Thus the circuit is made and broken with extreme rapidity and frequency. The secondary coil is insulated from the primar>- coil and its terminals are connected with the electrodes. The rapid making and breaking of the current in the primary 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 electrodes,as in the galvanic battery. The effects of faradism 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 ■ (muscular 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. Special electrodes of various shapes are used in applying the current to ditTerent parts of the body. A flat oval electrode, about 6 by 4 inches, is useful in applications to tho abdomen or spine; a small, pointed electrode, for singling out one muscle of a small area, or testing a nerve; a small oval bean-shaped electrode, fastened to a rubber-covered wiie. for swallowing in order to electrify the interior of the stomach ; an electrode shaped like a knitting-needle, with all but a half- inch of the tip insulated, for intrauterine use; a wire brush for special use with the faradic cur- Tent, etc. An interrupting electrode is so made "that with the thumb of the hand that applies the electrode the circuit may be closed and opened at -ivill for testing accurately. A special electrode is arranged for the insertion in its extremity of bib- ulous paper saturated with a drug in solution, which is carried into the ekin, when a current is passed, using this as the cathode. This is called ■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. Xormnlly the cathodal closure contraction of a muscle is greater than the anodal closure contraction. If degeneration has occurred in a nerve supplied to a muscle the anodal and cathodal closure con- tractions may be equal, or the anodal may be greater than the cathodal. Faradic contractility is less in muscle supplied by Vol. VI.— «9. a degenerated nerve than in one in a normal condition. Hy means of the kata- phonic electrode a medicine like iodide of potas- sium may be used locally in delinile quantity, a3 in a glandular enlargement; or cocaine may be applied over the |)ainful spot in a neuralgia or neuritis, or may be applied to the gum of a sen- sitive tooth before filling or extraction is ac- complished. licsidcs the use of electrization in several dis- eases, as stated under their own titles, in para- graphs on treatment, galvanization is of inuncnse valvie in exercising paralyzed muscles, securing their nutrition, and preventing their atrophv until relief of the central condition has been ac- complished or regeneration of nerves be<'n secured. In surgery the electrolytic action of the galvanic current is employed in destroying tumors; hyper- trophicd tissue, as in the nasal cavity; removing na'vi and birtluuarks, 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 Pacqvielin's cavitery 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, cim- sult Rockwell, Medical and Surgical Uses of Electricity (New York, 1896). See Dentistry. ELECTRIC-LIGHT BUG. See Fisiikiller. ELECTRIC LIGHTING. Illumination pro- duced by the conversion of electrical energy into light, practically always through the agency of either are or incandescent lamps. The electrical energy-, or electric current, is produced by dy- namos (see Dvx.vmo-Electric M.cniXERY), driven most frequently by either steam-engines or water-power, and sometimes by other forms of mechanical power, such as wind. The dynamos may produce direct or alternating current, of either high or low potential, which is brouglit to the lamps through a system of wires. The arc light is produced when an electric current passes across a space between two rods or pencils of car- bon which have been in contact and then slightly separated. (See Electric Arc.) In the incan- descent lamp an electric current passes through a carbon filameut mounted in a glass bulb, from which the air has been exhausted. The carbon filament offers considerable resistance to the cur- rent, so that the energy of the latter is trans- formed into heat. When the carbon is sufliciently heated it liecomes incandescent and emits light. The arc lamj) was the first to be dereloped, and while its incepti<m dates from the very beginning of the nineteenth century, its general use for lighting was only during the last twenty years of that <'entury and preceded that of the incan- descent lamp by only a few years. In l.S()2 one lamp of this kind was installed in a liglithoise at l)ungeness. Supplied with current from a ciunbrous Holmes magnetoelecfric machine, this light was in use for many years, and is credited with being the first electric lamp in regular ser- vice. Oranmie's dynamo of 1,S70 marked an era in electrical development, yet there were hut two electric-light exhibits at the Centennial Exhibi- tion at Philadelphia in 187(5. Only 2.3 years later the revised list of electric lighting exliibits at the Paris Exposition included 200 entries. In 1878 P;iul .latilochkolV's "electric candle' made a sen-
