RESPONSE BY VARIATION OF ELECTRICAL RESISTIVITY 54! 



only by the variation of resistance, but also by varying 

 polarisation and excitatory electromotive effects. 



The question still remains, What is the nature and 

 significance of this induced variation of resistance? As the 

 effects which have been referred to are generally seen to be 

 induced after excitation, and to constitute its after-effect, 

 does it follow that the diminution of resistance takes place 

 as a remote consequence of other excitatory changes ? 

 Or is it but a different manifestation of that fundamental 

 molecular change, induced by excitation, of which the 

 electromotive variation and change of form are other and 

 independent expressions ? 



I showed in the first chapter of this book that one 

 identical molecular change may be detected in different 

 ways, according to the method of observation. Thus the 

 same excitatory change is shown both in change of form 

 and in electromotive variation. That either manifestation 

 takes place in entire independence of the other is shown, 

 for instance, when the mechanical response of Mimosa or 

 Desmodium is restrained, under which condition the electro- 

 motive response proceeds as before. Excitatory changes, 

 similarly, may express themselves independently either by 

 electromotive variations or by changes of electric resistance. 

 It was, in fact, by means of the latter method, that of the 

 variation of resistance, that I first demonstrated the responsive 

 molecular changes which take place in inorganic matter. 1 



If living tissues, therefore, really respond to excitation 

 in a manner similar to the inorganic, it should be possible 

 to obtain from them response-records by a new method, 

 that of Resistivity Variation alone. In order to demonstrate 

 this inference, it will be necessary to show that such varia- 

 tion of resistance takes place immediately on excitation, 

 and not as an after-effect. We must, however, ascertain 

 whether this method of Resistivity Variation does or does 



1 Bose, De la GMralitt des Phenotnenes Moleculaires produits par F Elec- 

 tricitl sur la mattire Inorganique et stir la Matiere Vivante. (Travaux du 

 Congres International de Physique. Paris, 1900.) 



