some light on the obscure phenomena of
fatigue in animal tissues.

FOOTNOTES:

[10] Biedermann, _Electro-physiology_, p. 86.

[11] Biedermann, _loc. cit._

CHAPTER VI

PLANT RESPONSE--ON DIPHASIC VARIATION

Diphasic variation--Positive after-effect and positive response--Radial
E.M. variation.

When a plant is stimulated at any point, a molecular disturbance--the
excitatory wave--is propagated outwards from the point of its
initiation.

#Diphasic variation.#--This wave of molecular disturbance is attended by a
wave of electrical disturbance. (Usually speaking, the electrical
relation between disturbed and less disturbed is that of copper to
zinc.) It takes some time for a disturbance to travel from one point to
another, and its intensity may undergo a diminution as it recedes
further from its point of origin. Suppose a disturbance originated at C;
if two points are taken near each other, as A and B, the disturbance
will reach them almost at the same time, and with the same intensity.
The electric disturbance will be the same in both. The effect produced
at A and B will balance each other and there will be no resultant
current.

By killing or otherwise reducing the sensibility of B as is done in the
method of injury, there is no response at B, and we obtain the
unbalanced response, due to disturbance at A; the same effect is
obtained by putting a clamp between A and B, so that the disturbance
may not reach B. But we may get response even without injury or block.
If we have the contacts at A and B, and if we give a tap _nearer_ A than
B (fig. 26, _a_), then we have (1) the disturbance reaching A earlier
than B. (2) The disturbance reaching A is much stronger than at B. The
disturbance at B may be so comparatively feeble as to be negligible.

It will thus be seen that we might obtain responses even without injury
or block, in cases where the disturbance is enfeebled in reaching a
distant point. In such a case on giving a tap near A a responsive
current would be produced in one direction, and in the opposite
direction when the tap is given near B (fig. 26, _b_). Theoretically,
then, we might find a neutral point between A and B, so that, on
originating the disturbance there, the waves of disturbance would reach
A and B at the same instant and with the same intensity. If, further,
the rate of recovery be the same for both points, then the electric
disturbances produced at A and B will continue to ba