CHAPTER XVIII 



POLAR EFFECTS UNDER STRONG CURRENTS 



Abnormal polar reactions in Protozoa — Transformation of polar reaction 

 in leaf of Mimosa from Type II. to Type III. under strong current — 

 Further transformation to Type IV. under stronger current — Ex- 

 hibition of Type III. and Type IV. by leaflets of Mimosa, Biophytum, 

 and Averrhoa carambola — Law of polar action of strong currents. 



It has been shown in a preceding chapter that the charac- 

 teristic effect of a feeble current in various plants was 

 excitation at make of kathode, but that with a moderate 

 current there was excitation not only at the make of kathode 

 but also at the break of anode. These two types of effect 

 corresponded to those recognised in the case of animal 

 tissues under Pfluger's Law as Stage I. and Stage 11. It 

 will be remembered that in the case of Protozoa the polar 

 reactions have been found to be very different from these. 

 Thus Kiihne found that in Actinosphaerium excitatory con- 

 traction took place at the make of both kathode and anode, 

 and that excitation again took place at the break of kathode. 

 The excitatory formula here, then, may be expressed as 

 Km Kb Am. 



It will be noticed that we have here the abnormal 

 reactions of anode-make and kathode-break. Verworn has 

 corroborated and extended these observations. He further 

 finds that Amphistigma is excited by both anode and 

 kathode at make. There was apparently no effect at break. 

 The excitation formula in this case is therefore Km Am. 



From these abnormal effects it has been suggested 

 either that the polar effects in fibrillated and unfibrillated 



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