PLANT-AUTOGRAPHS—BOSE. 435 
failed to arrest the impulse. This result, at first sight, appears most 
convincing and has been universally accepted as a disproof of the 
existence of nervous impulse in Mimosa. A little reflection will, how- 
ever, show that under the particular conditions of the experiment the 
conducting tissue in the interior could not have been affected by the 
external application of the narcotic, the task beimg, in fact, as diffi- 
cult as narcotizing a nerve trunk lying between muscles by the appli- 
cation of chloroform on the skin outside. 
The question of nervous impulse in plants has thus to be attacked 
anew, and I have employed for this purpose twelve different methods. 
They all prove conclusively that the impulse in the plant is identical 
in character with that in the animal. Of these I shall give a short 
account of three differ- 
ent modes of investiga- 
tion. Itisobvious that 
the transmitted im- 
pulse in Mimosa must 
be of an excitatory, or 
nervous, character: 
(1) If excitation can 
be initiated and prop- 
agated without any 
physical disturbance. 
The central fact in the 
mechanical theory is 
the squeezing out of 
water for starting the 
hydraulic impulse. 
The hydromechanical Fic. 12.—Experimental arrangement for determination of velocity 
of transmission and its variation. Record is first taken when 
theory must necessa- stimulus is applied near the pulvinus at B (latent period) and then 
rily fall to the ground at a distant point on the leaf-stalk at A. Difference of two gives 
if cette is time for transmission from A to B. The band of cloth C is for 
uw excitation can € local application of warmth, cold, anesthetics, and poison. 
effected without any 
mechanical disturbance whatsoever. JI have shown that excitatory 
impulse is initiated under the polar action of current in the complete 
absence of any mechanical disturbance, the intensity of the current 
being so feeble as not to be perceived even by the very sensitive 
human tongue. 
(2) If it can be shown that physiological changes induce appro- 
priate variation in the velocity of transmission of the impulse. 
(3) If the impulse in the plant can be arrested by different physio- 
logical blocks by which nervous impulse in the animal is arrested. 
For the last two investigations the research resolves itself into the 
accurate measurement of the speed with which an impulse in the 
plant is transmitted, and the variation of that speed under changed 
