574 COMPARATIVE ELECTRO-PHYSIOLOGY 



of the increased excitability of A at the anode, and also 

 of the greater intensity of excitation conducted towards it, 

 the balance was disturbed, and the resultant response took 

 place by the enhanced galvanometric negativity of that 

 point. The responsive current thus constituted an increment 

 of the polarisation-current, as seen from the arrows, of which 

 the thin inner represents the polarisation and the thick outer 

 the responsive current. On now reversing the current again, 

 the right-hand end being made anode and more excitable, 

 the resultant response was found to take place by the 

 enhanced negativity of that point, thus again constituting 

 a polarisation increment (fig. 355). I give here two different 



FIG. 354. FIG. 355. 



Figs. 354, 355. Experimental Arrangements for Showing so-called 

 Polarisation-increment by the Joint Effect of Increased Excitability 

 at Anode and Enhanced Conduction of Excitation electrically Uphill 



sets of photographic records, obtained with the nerves of 

 fern and frog respectively. Balance was first obtained at 

 the beginning of the record, but on the passage of the 

 polarisation current, this balance was found to be disturbed. 

 When the right end of the balance was made anode, the 

 resultant response on excitation was Up, demonstrating the 

 enhanced excitability of the anodic point. When the right- 

 hand end, however, was made kathode, the balance was 

 upset in the opposite direction, that is to say, down, showing 

 that the left-hand anodic point was now the more excitable. 

 Fig. 356 gives a record of these responses as obtained from 

 the nerve of fern, and fig. 357 from the nerve of frog. The 

 responsive currents in these cases, it should be noted, are in 

 the same direction as the polarising current. 



