542 



NERVE. 



interior furnishes the good conducting core, the less concentrated liquid 

 in the wall is the moist envelope. All these models give polarisa- 

 tion effects, although external polarisation is eliminated ; hence these 

 effects must be due to the surface junction existing between the moist 

 envelope and the internal core. 1 The core is a better conductor 

 than the surrounding envelope, so that the passage of the polarising 

 current is followed by the formation of ions around the platinum wire 

 in Hermann's model, and both around and within the moist core of 

 Hering's model. 



Polarisation in Hermann's model. This is presumed to be of 

 the following character. At the anodic contact the current entering 



Hermann's model will 

 traverse the envelope, 

 and leave this liquid 

 to enter the better con- 

 ducting core. There 

 is, therefore, at this 

 point an internal cath- 

 ode (Fig. 280) for the 

 liquid envelope imme- 

 diately around the 

 core, and cathodic ions 



FIG. 280. Internal polarisation around metallic core of Her- are thus developed ill 



mann's model. The polarising current has been led this region. A similar 



through the model from A to 0. The polarisation after internal anode for the 

 effects are indicated by the ions and lines of current now. 



envelope occurs at 



the point where the current leaves the core to enter the envelope 

 (Fig. 281). At both these places, in the neighbourhood of the 

 better conducting core, electrolytic polarisation will be at its 

 maximum, and may be termed, from its position, "internal." The 

 ions of such internal polarisation under the surface anode (A), being, 



moist en velope 

 metallic 



core 



moist envelope 



FIG. 281. Internal polarisation effects around and within liquid core of such 

 a model as Hering's. The polarising current has traversed the complex 

 moist conductor from A to C. 



as far as the moist envelope is concerned, cathodic, will be H, i.e. 

 electro-positive to other portions of the moist conducting envelope. 

 Those under the surface cathode (C) will, for similar reasons, be o, 

 i.e. electro-negative. A current will thus pass through the moist envelope 

 from A to C, outside the core, and back in this from the portion 

 of core under the cathode to that under the anode as shown in 



1 Hermann, Arch. f. d. ges. Physiol., Bonn, Bd. vi. S. 319 ; Bd. xxxiii. S. 103. 



