286 PROF. J. C. BOSE ON ELECTRIC RESPONSE IN 
equally at the injured and uninjured ends, and the conditions 
of the experiment may thus undergo unknown variations. But 
by the block method, which has just been described, there is no 
injury, the plant is normal throughout, and any physiological 
change (which in plants will be exceedingly small during the 
time of the experiment) will affect it as a whole. 
Plant-Response a Physiological or Vital Response. 
I now proceed to a demonstration of the fact that whatever 
be the mechanism by which they are brought about, these 
plant-responses are physiological in their character. As the 
investigations described below will show, they furnish an 
accurate index of physiological activity of the plant. For it 
will be found that, other things being equal, whatever tends to 
exalt or depress this activity tends also to increase or diminish 
the electric response. 
T shall describe here a few crucial experiments only, in proof 
of the physiological character of electric response. The test 
applied by physiologists, in order to discriminate as to the 
physiological nature of the response, consists in experiments 
as to whether it is diminished or abolished by anesthetics, 
poisons, and exceedingly high temperatures, all of which are 
known to depress or destroy vitality. 
I shall therefore apply these same tests to plant-responses. 
Effect of Anesthetics and Poisons.—I took 30 leaf-stalks 
of horse-chestnut, and divided them into 3 batches of 10 each. 
One batch was kept in water, to serve as control experiment, 
another in chloroform water, and the third in 5 °/, solution 
of mercuric chloride. 
Average response of stalks kept in water —23 divisions. 
» » a chloroform—1 division. 
» » - mercuric chloride—zero oF 
very small. 
Similar results were obtained with leaf-stalks of plane-tree- 
I shall give later a continuous series of response-curves 
showing how, owing to progressive death from the action of 
poison, the responses undergo steady diminution till they are 
completely abolished. | 
Lffect of High Temperature.—A leaf-stalk is taken, and using 
the block method strong responses are obtained at both ends 
A and B. The stalk is now immersed for a short time in water 
