The power of conduction is also modified by age. In young specimens the conduct­ing power is low, the conductivity is at its maximum in fully grown organs; but a decline of conductivity sets in with age.

The tonic condition of a tissue has an influence on conductivity. In an optimum condition, the velocity is the same for feeble or strong stimulus. Excessive stimulation induces a temporary depression of the conduct­ing power.

The effects are different in a sub-tonic tissue: velocity of trans­mission increases with intensity of stimulus; after-effect of stimulus is to initiate or enhance the conduct­ing power. The conduct­ing path is canalised by stimulus.

VII.—ON ELECTRIC CONTROL OF EXCITATORY IMPULSE

By

Sir J. C. Bose.

I have in my previous works[L] 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.