. Electricity in diseases of the eye, ear, nose and throat . to C. and through the pa-tient X, by means of the electrodes D. and E. to the— supply wire, is controlled by the switch C. Whenthe switch is placed at B., the resistance of the wholecoil, added to that of the patient, allows only a verylittle current to pass, C. is moved towards A. to les-sen the resistance in order to increase the current asrequired. Current Controller.—See Figure 20. In the figure, the current divides at A. passesfrom A. to B. through the coil and through theshunt circuit; that is, from A. through the patient
. Electricity in diseases of the eye, ear, nose and throat . to C. and through the pa-tient X, by means of the electrodes D. and E. to the— supply wire, is controlled by the switch C. Whenthe switch is placed at B., the resistance of the wholecoil, added to that of the patient, allows only a verylittle current to pass, C. is moved towards A. to les-sen the resistance in order to increase the current asrequired. Current Controller.—See Figure 20. In the figure, the current divides at A. passesfrom A. to B. through the coil and through theshunt circuit; that is, from A. through the patient C. to B. There is the same drop in voltage inthe coil between A. and C. as in the patients cir-cuit; hence, the nearer C. is to B. the greater thecurrent through the patient. The coil A. B. is graduated in volts, under the 28 PHYSICS OP ELECTEICITY. condition of its definite resistance, to show the dropin voltage from A. to B. When a patient is throwninto the shnnt circuit, the resistance of A. B. isthereby lessened and the graduation is then not. Fig. 20. strictly accurate; but, on accoimt of the high resis-tance of the patient, the instrument serves as a rela-tive means of selecting the same indicated volts fora particular patient from day to day. The Rheotome.—An Instrument for makingand breaking either the direct or induced current. The wall plate rheotome is a clock work ar-rangement, in which the speed is regulated by a pen-dulum or otherwise. The number of interruptionsper minute varies with the speed of the clock andthe number of brushes on a revolving cylinder whichare made to come in contact with one of the threesprings. EHEOTOME AND EESISTANCE BOX. 29 In Figure 21, the current at C. passes throughB. when the instrument is not in action. When B. ismoved to 1, 2, or 3, the current passes through thespring D., the revolving cylinder A. and its one, two
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