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in my previous works 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 discovery of a similar phenomenon in the other.

As the transmission of excitation is a phenomenon of propagation of molecular disturbance in the conducting vehicle, it appeared that the excitatory impulse could be controlled by inducing in the conducting tissue two opposite 'molecular dispositions', using that term in the widest sense. The possibility of accomplishing this by the directive action of an electric current had attracted my attention for many years.

I have previously carried out an electric method of investigation, dealing with the influence of electric current on conductivity. The method of Conductivity Balance which I devised for this purpose was found very suitable. Isolated conducting tissues of certain plants were found to exhibit