ELECTROTONUS 237 



The effect of this imperceptible stimulus, then, which passed 

 through the nearer pair of leaflets, without giving any sign of 

 its presence, became suddenly ' developed ' on reaching the 

 further pair of leaflets, R (fig. 103), which v^^ere rendered more 

 excitable by the neighbourhood of the kathode. 



These peculiar variations of excitability, induced by the 

 action of the anode and kathode, as well as those caused by 

 other physical and chemical agencies, are exactly similar to 

 what are observed in animal tissues under the same influences. 

 They bring out, further, the essential unity of physiological 

 response, as seen in the highly differentiated protoplasm of 

 the animal and the undifferentiated protoplasm of plant 

 tissue. 



Summary 



The anode acts as a block to the transmission of stimulus. 



The effect of the kathode is opposite to that of the 

 anode. 



Motile excitability is diminished at or near the anode, so 

 that previously effective stimulus becomes ineffective. 



Motile excitability is exalted at or near the kathode. 

 Stimulus previously ineffective here becomes effective. 



