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Prof. J. C. Bose. Influence of Electric 



We have seen further that a perfect parallelism exists in the conductivity 

 variation induced in the plant and in the animal by the directive action of 

 the current. No explanation could be regarded as satisfactory which is not 

 applicable to both cases. Now with the plant we are able to arrange the 

 experimental conditions in such a way that the factor of variation of excita- 

 bility is completely eliminated. The various effects described about the 

 plant-tissue are, therefore, due entirely to variation of conductivity. The 

 parallel phenomena observed in the case of transmission of excitation in the 

 animal nerve must, therefore, be due to the induced change of conductivity. 



I may now briefly recapitulate some of the principal facts established in 

 this paper. 



The variation of conductivity induced by the directive action of current 

 has been investigated by two different methods : — 



(1) The method in which the normal speed and its induced variation are 

 automatically recorded ; 



(2) That in which the variation in the intensity of transmitted excitations 

 is gauged by the varying amplitudes of resulting responses. 



The great difficulty arising from leakage of the exciting induction current 

 into the polarising circuit was successfully overcome by the interposition of a 

 choking coil. 



The following summarises the effects of direction and intensity of an 

 electric current, on transmission of excitation through the conducting tissue 

 of the plant : — 



The velocity of transmission is found to be enhanced against the direction 

 of a feeble current, and retarded in the direction of the current. 



Feeble heterodromous current enhances conductivity, homodromous current, 

 on the other hand, depresses it. 



Ineffectively transmitted excitation becomes effectively transmitted under 

 heterodromous current. Effectively transmitted excitation, on the other 

 hand, becomes ineffectively transmitted under the action of homodromous 

 current. 



The after-effect of a current is a transient conductivity change, the sign of 

 which is opposite to that induced during the passage of current. The after- 

 effect of a heterodromous current is, thus, a transient depression, that of 

 homodromous current a transient enhancement of conductivity. 



When the intensity of current is gradually increased, the characteristic 

 conductivity variation is also increased, at first slowly, then rapidly. There 

 is a critical intensity of current above which the conductivity variation under- 

 goes a decline, culminating in an actual reversal. The effect of heterodromous 



