ANIMAL KLIXTRICITV. LECTURE V. II7 



as a polarisation increment.^ I am not satisfied with 

 either of these explanations, but think it more probable 

 that the v. Fleischl's deflection which you have just 

 witnessed is a case of what du Bois-Reymond 

 designated as " positive polarisation," and Hering 

 and Hermann subsequently showed to be an after- 

 anodic action-current." These are the several currents, 

 of which on this view only the after-anodic action- 

 current is apparent to you as a deflection in the 

 direction of the break. Seeing that the nerve and 

 galvanometer scale are facing you, and that the 

 connections are such as to make deflections on the 

 scale signify directions of current in the nerve (you 



^ Hermann, Handbuch, vol. ii., p. 167. 



- There is still a fourth possibility, i.e., that the effect in the 

 direction of the break may be due to a superiority of the 

 polarisation current after make over the polarisation current 

 after break. Although under the ordinary conditions of 

 physical experiment, the electrolysis by a break-current 

 exceeds that by the corresponding make-current, it is con- 

 ceivable that the polarisability of living matter may be such 

 that the longer make-current may produce a greater electrolysis 

 than the shorter break-current. 



The so-called " positive polarisation" or post-anodic action- 

 current, which is in the same direction as the exciting current, 

 is very readily intelligible as the effect of a post-anodic zinca- 

 tivity. It is easy to demonstrate. Its theoretical counter- 

 part during the passage of an exciting current, and opposed 

 to that current, is equally readily intelligible as the effect of 

 kathodic zincativity. It is, as far as I can see, insusceptible 

 of dived demonstration. 



