300 



ELECTRO-PHYSIOLOGY 



CHAP 



augmented resistance. But if polarisation occurs at the point at 

 which the lines of current pass from the fluid into the metal, 

 and if there is in consequence such a marked " resistance " 

 that the resistance due to unequal length of the lines of current 

 is practically out of consideration, there is evidently nothing 

 to prevent a wider diffusion of the current in the moist sheath 

 along the core (Hermann). 



As is obvious from the accompanying schema, a branch 

 current must flow in every extrapolar leacling-off circuit, at what- 

 ever point it is applied, in the direction of the polarising current 

 (Fig. 214). The following observations of Hermann (39, v. p. 



A 



270) point to the same result. " In Fig. 215 the lines Ah and Cg 

 show the path that would inevitably be taken by the current if 

 there were no polarisation, in view of the thinness of the moist 

 sheath and good conductivity of the metal core, in order to pass 

 from the electrode points A and C to the core. If polarisa- 

 tion occurs at h and g, the metal (e.g. platinum in dilute 

 sulphuric acid) would be charged with hydrogen at h, with oxygen 

 at g. The platinum point h, which is charged with hydrogen, 

 would then be electrically active towards the uncharged points 

 near it h-Ji^, and currents would be generated in the moist sheath 

 in the direction shown in the figure. These currents give off 

 hydrogen at h-Ji^ oxygen at h, but in a quantity insufficient to 

 neutralise the fresh hydrogen which is constantly being deposited 

 by the current. The charged points 7^ are now electromotive to 

 their uncharged neighbours /to, fresh currents /t^t., arise which 



