GENERAL SURVEY. 349 



In animal tissues, with feeble current it is found that 

 excitation takes place only at the kathode at make. On 

 moderately increasing the current excitation is found to 

 take place at the make of kathode and break of anode. 

 These effects are included in Pfluger's law of polar excita- 

 tion in animal tissues. I have shown that effects precisely 

 similar to these take place in the vegetal tissues. That is 

 to say, the laws of polar excitation in plant under feeble 

 and moderate currents are : 



I. With feeble current the kathode excites at make 

 and not at break. The anode excites at neither make nor 

 break. 



II. With moderately strong current, the kathode excites 

 at make and not at break. The anode excites at break and 

 not at make. 



The polar reactions in the undifferentiated protoplasm 

 of the plant body are thus identical with those of highly 

 differentiated animal tissues (p. 233). 



The effect of feeble ascending and descending currents 

 in the petiole of Mimosa are parallel to those in nerve-and- 

 muscle preparations. In both cases excitation takes place 

 earlier when the kathode is nearer to the responding organ. 

 As in animal, so also in Mimosa, single induction shock of 

 moderate intensity is, as regards polar actions, effective at 

 the commencement and not termination of the current 

 (p. 206). 



The sensitiveness of Biophytum to an electrical current 

 is remarkably high ; compared to the very sensitive human 

 tongue, the sensitiveness of Biophytum is about ten times 

 as great (p. 251). 



Pfluger's law cannot be taken as a complete statement 

 of the polar action of currents (p. 265). For strong currents 

 there are induced two additional types of reaction : 



III. Under the action of strong current, excitation 

 takes place at the make of kathode and make and break 

 of anode. 



IV. Under still stronger currents, excitation takes 



