THE DEDICATION 239 



the twining of tendrils, the heliotropic movements of some 

 towards and of others away from light, and the opposite 

 geotropic movements of the root and shoot, in the direction 

 of gravitation or away from it. My latest investigations 

 have established a single fundamental reaction which 

 underlies effects so extremely diverse. 



Finally, I may say a word of that other new and un- 

 expected chapter which is opening out from my demonstra- 

 tion of ' nervous ' impulse in plants. The speed with which 

 the nervous impulse courses through the plant has been 

 determined ; its nervous excitability and the variation of 

 that excitability have likewise been measured. The nervous 

 impulse in plant and in man is found exalted or inhibited 

 under identical conditions. We may even follow this 

 parallelism in what seem extreme cases. A plant carefully 

 protected under glass from outside shocks, looks sleek and 

 flourishing ; but its higher nervous function is then found 

 to be atrophied. But when a succession of blows is rained 

 on this effete and bloated specimen, the shocks themselves 

 create nervous channels and arouse anew the deteriorated 

 nature. 



A question long perplexing physiologists and psy- 

 chologists alike is that concerned with the mystery that 

 underlies memory. But now, through certain experiments 

 I carried out here, it is possible to trace ' memory im- 

 pressions ' backwards even in inorganic matter, such 

 latent impressions being capable of subsequent revival. 

 Again the tone of our sensation is determined by the 

 intensity of nervous excitation that reaches the central 

 perceiving organ. It would theoretically be possible to 

 change the tone or quality of our sensation, if means could 

 be discovered by which the nervous impulse would become 

 modified during transit. Investigation on nervous impulse 

 in plants has led to the discovery of a controlling method, 

 which was found equally effective in regard to the nervous 

 impulse in animal. 



Thus the lines of physics, of physiology and of psychology 



