CHAPTER XLVIII 



REVIEW OF RESPONSE OF NERVE AND RELATED 

 PSYCHOLOGICAL PHENOMENA 



Transmission of excitation in plants Vegetal nerve Similar variations of 

 receptivity, conductivity, and responsivity, under parallel conditions in plant 

 and animal nerves Conductivity balance After-effect of section on con- 

 ductivity and excitability Function of vegetal nerve in plant-economy 

 Laminae of plant form a catchment-basin for stimulus Motile response of 

 nerve Molecular cycle and characteristic changes in response of nerve 

 Effect of fatigue on transmitted excitation- Similarity of excitatory molecular 

 changes in both afferent and efferent nerves Multiple response induced by 

 strong stimulus in nerve Multiple excitations in nerve during drying 

 Individual contractile responses to constituent tetanising shocks Negative 

 after-effect on abrupt cessation of tetanisation Extra-polar effects similar in 

 plant and animal nerve Inadequacy of Pflliger's Law Under feeble E.M.F. 

 excitability enhanced by anode and depressed by kathode Demonstration by 

 subjective response Under feeble current excitation travels better against 

 than with it Response by variation of electrotonic current due to algebraical 

 superposition of excitatory effect Physico-physiological basis of sensation 

 Identification of positive tone of sensation with hydro-positive wave and 

 negative tone of sensation with negative wave Natural and artificial induc- 

 tion of dissociation of sensation Physical explanation of Weber- Fechners 

 Law Quality of sensation also a factor Conversion from painful to pleasur- 

 able and vice versa at will by electrotonus Memory as an after-effect of 

 stimulus Persistent after-sensation Revival of latent memory-image through 

 differential excitation induced by diffuse stimulation Same effects demon- 

 strated in the inorganic. 



THE next subject to be reviewed is that of the conduction 

 of stimulus. It has been supposed that plants do not con- 

 duct excitation by the transmission of protoplasmic changes, 

 as certain animal tissues are known to do. Even in the well- 

 known case of Mimosa^ where stimulus is seen to induce move- 

 ment at a distance, this was supposed to be the result of hy- 

 dro-mechanical disturbance. This conclusion has been shown, 

 however, to be erroneous, for pure hydrostatic disturbance 



