A laboratory manual of electrotherapeutics . the rapidity of interruptions by this method canbe considerably increased. But we have yet failed to findan instrument with a spring vibrator in which the numberof interruptions can be made to reach 200 per number of interruptions in an induction coil currentis one of the important elements in producing physio-logical and therapeutic effects, since the greater theirfrequency the more the sharp and irritating quality of thecurrent is reduced, and the more soothing it is in itsinfluence. Numerous attempts have been made to securemore rapid
A laboratory manual of electrotherapeutics . the rapidity of interruptions by this method canbe considerably increased. But we have yet failed to findan instrument with a spring vibrator in which the numberof interruptions can be made to reach 200 per number of interruptions in an induction coil currentis one of the important elements in producing physio-logical and therapeutic effects, since the greater theirfrequency the more the sharp and irritating quality of thecurrent is reduced, and the more soothing it is in itsinfluence. Numerous attempts have been made to securemore rapid and uniform interruptions by other arrange-ments than that of the spring vibrator, but so far thedevices have been either too complex or expensive tocreate much demand for them. The Englemann segmentedrotary interrupter, run by an electric motor, is capable ofgreatly increasing the number of interruptions and withperfect uniformity, but its cost places it beyond the reachof the majority of those using induction coils. 6 S: LABORATORY MANUAL. Fig. 37. Form of Induction Coil, used in thisLaboratory. The Secondary Coil.—The secondary coil is theinduction coil proper, and the current derived from it canbe caused to vary considerably in strength and quality at the will of the op-erator. This coil isalways made of finerwire than that usedin the primary usually has a muchgreater number ofturns also and thelength of the wire is,of course, propor-tionately our laboratory ex-perimental coils thesecondary is woundwith number 31 wire and has 3 layers, the length of wireused being about 180 feet, the resistance of which is about35 ohms. Most secondary coils for physicians use arenow made of still finer wire. Number 36 is preferred bymany, and the number of layers is as many as eight or tenor even more. The finer the wire the greater the number of turnsmade in each layer, and as each additional turn of wireadds one to the frequency with which the lines of magneticforce
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