5/0 COMPARATIVE ELECTRO-PHYSIOLOGY 



in relation to it being anode. On excitation the responsive 

 current was in the opposite direction to the permanent 

 current, in consequence of the induced depression of the 

 kathode E' or the induced enhancement of excitability at 

 the relative anode E. In fig. 350 are given the records of 

 these effects. Two different experiments were carried out, 

 on two different specimens of plant nerve, whose records are 

 given in a and , fig. 350. In each of these we observe, first, 



FIG. 350. Photographic Records of Response, illustrating the Enhance- 

 ment of Excitability at Anode, and Depression at Kathode, under 

 Feeble Acting E.M.F\ in two Specimens of Nerve of Fern a and b 



Before application of polarising current there was no resultant response in 

 either case. When E' was made anode, there was an up-response, 

 indicating enhanced excitability of that point. The dotted arrow ^ 

 seen below shows the direction of polarising current. The responsive 

 current is then opposite in direction to the polarising current. When 

 E' is made kathode the resultant response is down, showing depression 

 of the excitability of the point. The responsive current is here also 

 opposite in direction to the polarising current. 



the enhanced excitability due to E' being made anode, 

 which gives rise to up-responses, opposite in direction to the 

 permanent current, shown by the dotted arrow below. The 

 second pair of responses in each case shows the depression 

 of excitability at the kathodic point E', which is tantamount 

 to enhancement of excitability at the relative anode E. An 

 inspection of figs. 348 and 349 will show that the responsive 

 current is always in a direction opposite to that of the existing 

 polarising current, thus constituting the so-called polarisation 



