434 



Messrs. F. G-otch. and G-. J. Burch. 



" Note on the Electromotive Force of the Organ Shock and the 

 Electrical Besistance of the Organ in Malapterurus eledricus. 9 * 

 By Francis Gotch, M.A., F.B.S., and G. J. Burch, M.A. 

 Oxon. Beceived July 18, — Bead November 16, 1899. 



(From tlie Physiological Laboratory, Oxford.) 



Electrometer Records of the Organ Shock. 



In the month of March of the present year, 1899, the Committee of 

 the Corporation Museum, Liverpool, kindly placed at the disposal of 

 one of us (F. G.) two living specimens of Malapterurus eledricus. They 

 were exhibited at a lecture delivered in London at the Boyal Institu- 

 tion on March 17. One of the fish died from accidental injury, the 

 other was employed by us for the purpose of determining the electro- 

 motive force of the organ shock, and for investigating such other points 

 of interest as were feasible. 



We decided to employ for the determinations the special capillary 

 electrometer made by one of us (G. J. B.), which we had utilised in our 

 researches upon, the electrical phenomena of nerve.* Our previous 

 work upon the organ of Malapterurus rendered it certain that consider- 

 able precautions would have to be adopted in connection with this 

 instrument, since it was a much more sensitive one than those we had 

 used in the researches described in our previous paper upon the sub- 

 ject.! It was therefore first necessary to make a number of prelimin- 

 ary experiments in order to reduce the extent of any excursion due to 

 the organ shock within such limits that it could be recorded. Several 

 trials with different voltages resulted in our employing a non-inductive 

 shunt of three incandescent lamps ; these were placed in parallel be- 

 tween the electrometer connections and had a combined resistance of 

 26 "6 ohms. We diminished the size of the record still further by re- 

 placing the high objective of the projecting microscope by a lower 

 power, Zeiss, B. 



Our previous experiments made in 1895 showed us that the organ 

 shock developed so rapidly that the records then obtained were all too 

 steep to admit of accurate analysis. It seemed certain, therefore, that 

 the recorded curves, due to the rise and fall of the meniscus, would 

 have to be of a more prolonged type in order that the rate of develop- 

 ment of the electromotive force of the shock might be deduced from 

 their analysis. 



In the hope of obtaining curves of a sufficiently prolonged character, 

 both the phy sical and the physiological conditions of experiment were 



* < Eoy. Soc. Proc.,' vol. 63, p. 300, 1898. 

 f 'Phil. Trans.,' B, vol. 187 (1896), p. 347. 



