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The Influence of Homodromous and Heterodromous Electric 



Currents on Transmission of Excitation in Plant and Animal. 

 By Prof. J. C. Bose, M.A.. D.Sc, C.S.I., CLE., Presidency College, Calcutta. 



(Communicated by Prof. S. H. Vines, F.R.S. Received June 2, 1914.) 



I have in a previous paper* described investigations on the conduction of 

 excitation in Mimosa pudica. It was there shown that the various 

 characteristics of the propagation of excitation in the conducting tissue of 

 the plant are in every way similar to those in the animal nerve. Hence it 

 appeared probable that any newly found phenomenon in the one case was 

 likely to lead to the discovery of a similar phenomenon in the other. 



A problem of great interest which has attracted my attention for several 

 years is the question whether, in a conducting tissue, excitation travels 

 better with or against the direction of an electric current. The experimental 

 difficulties presented in the prosecution of this enquiry are very numerous, 

 the results being complicated by the joint effects of the direction of current 

 on conductivity and of the poles on excitability. As regards the latter, 

 the changes of excitability in the animal nerve under electrotonus have been 

 demonstrated by the well-known experiments of Pfliiger. In a nerve-and- 



_rD 



p s 



(a) 



A B C V ^ 



(b) 



Fig. 1. 



muscle preparation, the presence of a pole P is shown to induce a variation of 

 excitability of a neighbouring point S. When P is kathode, the excitability 

 of the point S, near it, is enhanced ; stimulation of S, previously ineffective, 

 now becomes effective, and the resulting excitation is transmitted - to M, 



* Bose, " An Automatic Method for the Investigation of Velocity of Transmission of 

 Excitation in Mimosa? ' Phil. Trans.,' B, vol. 204 (1913). 



VOL. LXXXVIII. — B. 2 Q 



