Response in the Living and Non-Living

by Jagadis Chandra Bose

Effect of temperature.—Similar considerations lead us to expect that a moderate rise of temperature will be conducive to increase of response. This is exhibited in the next series of records. The wire at the low temperature of 5° C. happened to be in a sluggish condition, and the responses to vibrations of 45° to 90° in amplitude were feeble. Tepid water at 30° C. was now substituted for the cold water in the cell, and the responses underwent a remarkable enhancement. But the excessive molecular disturbance caused by the high temperature of 90° C. produced a great diminution of response ([fig. 65]).

Fig. 65.—Responses of a Wire To Amplitudes of Vibration 45° and 90°

(a) Responses when the wire was in a sluggish condition at temperature of 5° C.
(b) Enhanced response at 30° C.
(c) Diminution of response at 90° C.

Diphasic variation.—It has already been said that if two points A and B are in the same physico-chemical condition, then a given stimulus will give rise to similar excitatory electric effects at the two points. If the galvanometer deflection is ‘up’ when A alone is excited, the excitation of B will give rise to a downward deflection. When the two points are simultaneously excited the electric variation at the two points will continuously balance each other. Under such conditions there will be no resultant deflection. But if the intensity of stimulation of one point is relatively stronger, then the balance will be disturbed, and a resultant deflection produced whose sign and magnitude can be found independently by the algebraical summation of the individual effects of A and B.

It has also been shown that a balancing point for the block, which is approximately near the middle of the wire, may be found so that the vibrations of A and B through the same amplitude produce equal and opposite deflection. Simultaneous vibration of both will give no resultant current; when the block is abolished and the wire is vibrated as a whole, there will still be no resultant, inasmuch as similar excitations are produced at A and B.

After obtaining the balance, if we apply an exciting reagent like Na₂CO₃ at one point, and a depressing reagent like KBr at the other, the responses will now become unequal, the more excitable point giving a stronger deflection. We can, however, make the two deflections equal by increasing the amplitude of vibration of the less sensitive point. The two deflections may thus be rendered equal and opposite, but the time relations—the latent period, the time rate for attaining the maximum excitation and recovery from that effect—will no longer be the same in the two cases. There would therefore be no continuous balance, and we obtain instead a very interesting diphasic record. I give below an exact reproduction of the response-curves of A and B recorded on a fast-moving drum. It will be remembered that one point was touched with Na₂CO₃ and the other with KBr. By suitably increasing the amplitude of vibration of the less sensitive, the two deflections were rendered approximately equal. The records of A and B were at first taken separately ([fig. 66], a). It will be noticed that the maximum deflection of A was attained relatively much earlier than that of B. The resultant curve R′ was obtained by summation.