ELECTROTONUS 



233 



FIG. 99. Effect of Anode as Block. 

 A, Anode ; k, Kathode 



The progressive wave of excitation, 

 initiated at x , stopped by anode, 

 one pair of leaflets to its left. 



at the kathode. Thermal 

 and the excitatory wave was 



either with greater velocity or to a greater distance ; but if 

 conductivity be in any way diminished, the distance to which 

 the excitatory disturbance will be transmitted, will be corre- 

 spondingly reduced. 



The anodic block. — In order to demonstrate the de- 

 pressing action of the anode, I took a leaf of Biophytum, and 

 sent a current through portions of it, entering at A, the anode, 

 and leaving at K, or kathode 

 (fig. 99). The E.M.F. used was 

 two volts, and was thus insuffi- 

 cient to cause responsive action. 

 In this and the following expe- 

 riments, it will be understood, 

 unless the contrary is stated, 

 that the intensity of the elec- 

 trotonic currents was not such 

 as to create any direct action 

 stimulus was now applied at x, 

 found to be stopped at a distance of one pair of leaflets to 

 the left of A. This shows that the depressing effect of the 

 anode acts as a block to the passage of stimulus, and that 

 such depressing action extends to some distance beyond the 

 anode itself. 



Experiments showing differences of anode and 

 kathode. — In order to show that the kathode acts differently 

 from the anode, not offering 

 a block, but rather facili- 

 tating the passage of stimu- 

 lation, I performed another 

 experiment on a leaf similar 

 to the last. In that case, 

 the anode was near the 

 point of application of 

 stimulus. I now made the 

 nearer electrode kathode. 



On next applying the usual stimulus, the excitatory wave 

 passed on through the kathodic area, producing successive 



1 



^fPM 



Fig. 100. Experiment showing the 

 Transmission of Excitatory Wave 

 through Kathodic Area, and its Stop- 

 page by the Anode 



Stimulus was applied at x . 



