Two Lectures on Tumours of the Larynx; Their Pathology, Symptoms, and Treatment, with Illustrative Cases
Authors: D. Newman
Journal: BMJ (1886)

to Dr. Stone that an alternating current might be expected to show too low a resistance, because of the electro-chemical capacity of the body which it would treat like conductivity.4.There was, probably, also considerable self-induction, a term which he was free to confess involved much difficulty.Self-indutction.-The possibility that self-induction played a con- siderable part in the actions now under consideration, was very strongly brought to mind by the highly suggestive Presidential Address, delivered by Professor Hughes to the Society of Telegraph Eng,ineers and Electricians, on January 28th, 1886.Professor Hughes had sketche(d the history of the discovery of self-induction in the following words."Induced, or secondary currents, in a near but independlent circuit, were discovered by Faraday in 1831 ; and the phenomenon of the self-inductioni of au electric current in its own wire, was observed by Henry in 1832, and traced to its cause in 1834 by Faraday, who proved that, -on sending a current through a wNire, a momentary induced currenit, ini the opposite direction, is evoke(d in its own wire ; also tlhat, on the cessation of the primary current, a second induced, or ' extra current' is excited in the direc- tion of the primary.The effect is greatly augmentedl when the wire forms a coil, as we then have, in addition, the reaction of superposed cuirrents ; but the effect exists to a great extent, even when the wire forms but a single loop, or a straight wire with the earth forming the returning portion of the loop, as in all telegraph lines."Dr. Stonle saidl tlhat, though tlhere was still some controversy as to the mathematical interpretation of the facts brought forward by Pro- fessor Hughes, he believel that they pointed to a new direction, in which researchl rnight be )rosecuted by physiologists.Professor Hughes divide(d the cu.rent ilnto stable andt variable periods ; the con- tinuous cuirrent was in the stable, the alternated and interrupted in the variable perio(l.It was in the latter that iniduction took place.Instead of the time-honoured Neef's bammer of the induction-coil, Professor Hughes employed his own invention, the microphone, or a snmall colntact-breaking clock.This allowed the use of the ordi- nary nmeter-bridge for measuring resistance, in combination with the sonometer, by which means Inot only resistance, but self-induction coul(d be mcasured.A straight meter-bridge, with a platinum silver-wire, and two sliding conitacts, was showli, joined up with the latest form of the Hughes sonometer, consisting of two concentric coils of wire, on cylin- drical bobbins, the innier being movable round an axis passinig through the diameter of the outer coil.When the two coils were at right angles to each other, a pointer, attached to the inner one, indicated zero, there being no self-induction betweeni them inthis position.The connections formed a most ingeinious combination of the meter-bridge with the sonometer.A current, slowly interrupted bythe contact-breaking clock, was then passed through a standard resistance, and through the samne muan as had been before experimented on, the series of tele- phones distributed about the room still acting as sensitive galvano- meters in the bridlge.Approximate silence was obtained in the tele- phones by means of the sliding contacts, which was rendered coin- plete by rotating the moving incdex and coil of the sonometer, until an equal and opposite amilount of self-induction to that of the human body had been introduced.With this instrument, which had only recently come into his hands, Dr. Stone hoped to be able to balance resistance and self-induction separately ; but, as yet, the time duriing which it had been at his dis- posal had been too short to allow him to arrive at complete measurements.The method of using the instrument was, however, successfully deemonstrated.Genteral Considerationts.-In bringing his lectures to a conclusion, Dr. Stone expressed his conviction that there was a great field open for research in this direction.The whole foundation of physiological electricity required to be strengthened and re-examined.It was, indeed, a stately building, but its physical basis was unsafe, and, uIntil this was made firm, the entire superstructure was in danger.If this