CHAPTER XVII 



ON CONDITIONS OF REVERSAL OF NORMAL POLAR 

 EFFECTS IN LIVING TISSUES 



Effect of high E.M.F. — Effects at two stages, A and B — Experimental verifica- 

 tion of ^ stage effect — Similar effects seen in protozoa — Experimental verifi- 

 cation of complete reversal at ^ stage — Law of polar effects under high E.M.F. 

 — Investigation on polar effects by death-response — Reversal of polar effects as 

 due to fatigue, or tissue-modification — Investigation of polar effects by glow- 

 response of fireflies. 



The phenomena ot polar excitation which have been 

 observed in animal tissues are summarised in the formula 

 which is known as Pfliiger's Law, viz. that excitation takes 

 place at the kathode at make, and the anode at break. It 

 has been found, however, by Kiihnc, Verworn, and others, 

 that in the case of the protozoa the polar effects are exactly 

 the opposite ; that is to say, in these instances, it is the 

 anode which excites at make. The inference has hence been 

 drawn, that Pfliiger's law was inapplicable in the case of un- 

 fibrillated protoplasm. 



That this assumption, however, is incorrect, I have 

 already shown, by the fact that the undifferentiated proto- 

 plasm of the plant-body gives rise to polar effects which are 

 in every way identical with the normal polar effects seen in 

 animal tissues. 



It occurred to me that the sttidy of polar effects in plants 

 might throw some light on this anomaly, and that I might 

 thus be able to trace out the stages by which the one effect 

 was gradually transformed into the other, determining further 

 the conditions which were effective in predisposing a tissue 

 towards this reversal. 



Effect of high E.M.F. — In carrying out this investigation, 



