

CHAPTER IX 



DETECTION OF PHYSIOLOGICAL ANISOTROPY BY ELECTRIC 



RESPONSE 



Anomalies in mechanical and electrical response Resultant response determined 

 by differential excitability Responsive current from the more to the less 

 excitable Laws of response in anisotropic organ Demonstration by means 

 of mechanical stimulation Vibrational stimulus Stimu'ation by pressure 

 Quantitative stimulation by thermal shocks. 



IT has been customary, as we know, to ascribe the varied 

 movements of plant-organs under external stimulus, to the 

 presence of different specific sensibilities ; and, indeed, it 

 would seem at first sight impossible to reduce such highly 

 complex and apparently unrelated phenomena, to the terms 

 of a single fundamental reaction, common to all alike. There 

 is no denying, for instance, that certain plant-organs, when 

 acted on by light, bend towards it, and others away. I have 

 elsewhere shown, 1 however, that all these diverse movements 

 are clearly traceable to one fundamental excitatory reaction, 

 and that the different effects observed are due merely to the 

 differential excitabilities of various parts of the structure ; 

 and that the resultant movement is in all cases brought 

 about by the greater contraction of the more excited side. 



Passing next to the electrical response of living tissues, 

 animal and vegetable, we encounter many anomalies. Not 

 only will one tissue give positive, and another negative 

 response, but we find also that the same tissue will give 

 sometimes one and sometimes the other. These apparent 

 inconsistencies are often due, as we shall find, to the differential 

 excitability of anisotropic structures a factor in the problem 

 which has not hitherto been recognised. An investigation on 



1 Bose, Plant Response. 



