excitable, and excitation was caused by the discharge of ·1 microfarad condenser charged to ·3 volt.
Stimulation by Induction-shock
Excitation may be induced by means of a single or repeated shock from an induction coil. In my own experience I was at first under the impression that this mode of stimulation was not suitable for repeated quantitative experiments, as I found that the plant was liable to become insensitive owing to the fatigue or injury caused by the shock. Later, however, I was able to trace this difficulty to the
Fig. 10.—Record of responses to stimulation by condenser discharge.
employment of an intensity of shock which was in excess of a certain critical value. I had in fact been misled by the prevailing belief that the excitability of the plant was considerably lower than that of the animal. Hence I employed an intensity of current which was unnecessarily high. This induced fatigue and consequent insensitiveness. Afterwards I discovered that in so far as its sensitiveness to electrical stimulation was concerned, Mimosa was in no way inferior to the animal. Quantitative results will be given later, in justification of this statement. Avoiding, then, an intensity of stimulus which was too great, and allowing proper resting-intervals, I found that the efficiency of induction-shock as a mode of stimulation was all that could be desired. It has also the great advantage of
