334 ELECTRO-PHYSIOLOGY CHAP. 



is inconceivable that there should be reciprocal neutralisation of 

 anodic and katho'dic polarisation, unless the two ions are, so to 

 speak, in immediate juxtaposition. Is it, however, so impossible 

 that the two polarisations should neutralise their respective 

 action upon the living matter, when they merely arise at either 

 border of a visible fibril ? Bernstein further supposes that his 

 series of molecules behave in regard to spatial distribution of 

 polarisation exactly like Hermann's core-model, or the equivalent 

 medullated nerve-fibre, and he refers the excitation at closure 

 and opening of the current solely to the appearance of negative 

 and disappearance of positive ions within the collective molecules 

 of the living matter under the electrode a view that recalls the 

 electrolytic theory of v. Bezold, where electrical excitation is 

 explained by (or at any rate referred to) chemical stimulation 

 from the separated ions. 



It is, however, under any circumstances difficult to explain 

 the opening excitation, as also the alterations of excitability 

 that occur during the passage of current, by a purely chemical 

 theory of electrical stimulation, and Bernstein was compelled to 

 lay down further postulates as to the nature and behaviour of 

 the liberated ions. These are : 



(i.) The negative ion at the kathode (oxygen, or an oxygenated 

 element) is the cause of the closing excitation. 



(ii.) This ion is constantly reduced by a chemical process, in 

 ratio with the mass in which it is developed. 



(iii.) The positive ion at the kathode produces no excitation ; 

 it is not therefore reduced, but accumulates. 



(iv.) The internal polarisation, more particularly at the anode, 

 neutralises the current in the excitable, polarisable conductor, 

 save for a proportionate remainder provided the polarisation 

 is not maximal. 



The active oxygen separated off from the excitable molecules 

 at the region of the kathode tears apart the labile molecules by 

 its oxidising action, whereupon the intramolecular oxygen also 

 conies into play and induces excitation. The alterations of 

 excitability during polarisation are taken by Bernstein to mean 

 that the molecule charged with negative ions (oxygen) is more 

 easily split up, that charged with positive ions less easily ruptured 

 than the unaltered molecules. More particularly in the kathodic 

 region, throughout the closure of the current, there is a slow but 



