ELECTROTONUS 575 



On referring to the experiments on polarisation increment 

 and decrement which have just been described it will be noticed 

 that the excitatory reaction is the same in both cases, taking 

 place by the enhanced galvanometric negativity of the more 

 excitable anodic point. The seeming difference in the 

 electrotonic variation in the two cases lies simply in the fact 

 of the different dispositions of the galvanometer. This 

 occupied, in the first case, the position of a shunt in the 

 polarisation-circuit, while in the second it was placed in 

 series. 



From the investigations which have been described, we 

 shall now find ourselves in a position to explain the various 



FIG. 356. FIG. 357. 



FlG. 356. Photographic Record of Responses in Nerve of Fern, under 

 Anodic and Kathodic Action, as described in Figs. 354 and 355. 

 The upsetting of the balance is upwards, when the right-hand end of 

 the balance is made anode, proving the enhanced excitability thus 

 induced. Resultant response downwards when the right-hand end of 

 the balance is made kathode. 



FIG. 357. Photographic Record of Similar Effects in Nerve of Frog. 



experiments of Hermann and Bernstein, and to show that 

 these, although apparently conflicting, are really mutually 

 consistent. First, then, to take Hermann's experiment, and 

 referring back to figs. 341 and 342, in which the galvanometer 

 is placed in series in the polarisation-circuit, we find this to 

 be an instance in which we have to deal almost exclusively 

 with the effect of anode and kathode on excitability. 

 Simultaneous excitation of the anodic and kathodic points 

 by alternating induction currents, induces greater excitation, 

 and consequent enhanced negativity of A. The responsive 



