334 Professor Oliver Lodge [June 1 , 



Prof. Gotcli, at Liverpool, I too have tried the nerve and muscle pre- 

 paration of the frog, Fig. 15, and we find that an excessively violent 

 stimulus of a rapidly alternating character, if pure and unaccompanied 

 by secondary actions, produces no effect — no stimulating effect, that 

 is, even though the voltage is so high that sparks are ready to jump 

 between the needles in direct contact with the nerve. 



All that such oscillations do, if continued, is to produce a tem- 

 porary paralysis or fatigue of the nerve, so that it is unable to 

 transmit the nerve impulses evoked by other stimuli, from which 

 paralysis it recovers readily enough in course of time. 



This has been expected from experiments on human beings, such 

 experiments as Tesla's and those of d'Arsonval. But an entire 

 animal is not at all a satisfactory instrument wherewith to attack 

 the question ; its nerves are so embedded in conducting tissues that 

 it may easily be doubted whether the alternating type of stimulus ever 

 reaches them at all. By dissecting out a nerve and muscle from a 

 deceased frog after the historic manner of physiologists, and applying 



Fig. 15. 



Experiment of Gotch and Lodge on the physiological effect of rapid 

 pure electric alternations. Nerve-muscle preparation, with four 

 needles, or else non-polarisable electrodes applied to the nerve. 

 C and D are the terminals of momentary rapidly alternating electric 

 current from a conductor at zero potential, while A and B are the 

 terminals of an ordinary very weak galvanic or induction coil 

 stimulus only just sufficient to make the muscle twitch. 



the stimulus direct to the nerve, at the same time as some other w r ell 

 known y^- of a volt stimulus is applied to another part of the same 

 nerve further from the muscle, it can be shown that rapid electric 

 alternations, if entirely unaccompanied by static charge or by resultant 

 algebraic electric transmission, evoke no excitatory response until 

 they are so violent as to give rise to secondary effects such as heat or 

 mechanical shock. Yet, notwithstanding this inaction they gradually 

 and slowly exert a paralysing or obstructive action on the portion of 

 the nerve to which they are applied, so that the nerve impulse excited 

 by the feeble, just perceptible yl^-volt stimulus above is gradually 

 throttled on its way down to the muscle, and remains so throttled for 

 a time varying from a few minutes to an hour after the cessation of 

 the violence. 



Among trigger methods of detecting electric radiation, I have 

 spoken of the Zehnder vacuum tubes; another method is one used 

 by Boltzmann.* A pile of several hundred volts is on the verge of 

 charging an electroscope through an air gap just too wide to break 



Wied. Ann., xl. p. 399. 



