14 RESPONSE IN THE LIVING AND NON-LIVING 
It may, however, be that this limitation is not justi- 
fied, and surely, at least until we have explored the 
whole range of physical action, it cannot be asserted 
definitely that a particular class of phenomena is by its 
very nature outside that category. 
Electric response in plants,——But before we proceed 
to the inquiry as to whether these responses are or are 
not due to some physical property of matter, and are to 
be met with even in inorganic substances, it will perhaps 
be advisable to see whether they are not paralleled by 
phenomena in the transitional world of plants. We 
shall thus pass from a study of response in highly com- 
plex animal tissues to those given under simpler vital 
conditions. 
Electric response has been found by Munck, Burdon- 
Sanderson, and others to occur in sensitive plants. But 
it would be interesting to know whether these responses 
were confined to plants which exhibit such remarkable 
mechanical movements, and whether they could not 
also be obtained from ordinary plants where visible 
movements are completely absent. In this connection, 
Kunkel observed electrical changes in association with 
the injury or flexion of stems of ordinary plants.' My 
own attempt, however, was directed, not towards the 
obtaining of a mere qualitative response, but rather to 
the determination of whether throughout the whole 
range of response phenomena a parallelism between 
animal and vegetable could be detected. That is to 
1 Kunkel thought the electric disturbance to be due to movement of 
water through the tissue. It will be shown that this explanation is in- 
adequate. 
