II 8 PLANT RESPONSE 



Parallel types of response in living organic, and in 

 inorganic matter. — Such being the difficulties involved in 

 the explanation of a single class of phenomena, on the 

 chemical hypothesis of assimilation and dissimilation, it may 

 be well next to turn our attention to the conclusions suggested 

 by the observation of response in matter generally. And for 

 this purpose it is best to take the responses obtained from 

 inorganic matter in particular, the hypothetical assimilation 

 and dissimilation being in that case out of the question. 

 With regard to the mode of observation, I have already 

 explained how the molecular derangement consequent on 

 stimulus may be studied, either (i) by recording the change 

 of form ; or (2) by recording the variation of conductivity ; 

 or (3) by recording the electromotive variation. 



As an example in the first place of responsive contraction 

 in inorganic matter, we may select for our investigation the 

 response of india-rubber, under thermal stimulation. In this 

 case, chemical changes, either up or down, are impossible. 

 The second, or conductivity variation method, may be used 

 in the case of metallic powders, the stimulus being that of 

 Hertzian radiation. In this case also chemical action 

 may be excluded, the experimental material being usually 

 placed in naphtha. In the third case, again, where response is 

 obtained by means of the electromotive variation, under 

 mechanical stimulus, the substance used is platinum, the 

 most chemically inactive of metals, electrolytic contacts being 

 made by water. 1 The possibility of chemical action is thus 

 reduced to a minimum, and the assimilatory change entirely 

 excluded. 



It will be found, however, that in all these cases of in- 

 organic response, in which substances, physically and chemi- 

 cally widely unlike, are subjected to diverse forms of stimula- 

 tion, and have their responses tested and recorded by absolutely 

 different methods, the results obtained are exactly parallel. 

 All alike, when sufficient intervening periods of rest are 



1 For details of these investigations and results, see Bose, Response in the 

 Living and Non-Living. 



