96 



ANIMAL ELPXTRICITV.— LECTURE IV. 



consisted of a platinum wire in a solution of zinc 

 sulphate, and in that case there was no marked 

 difference of magnitude between the anodic and the 

 kathodic extrapolar currents. 



Here is another core-model, composed of a zinc 

 wire in a solution of sodium chloride ; in this case 

 the effects are unequal. On closure of the polarisinor 



OT volt 



o'3 



0-4 



0-5 

 0-6 



Fig. 42 (2369). — Extra-polar ( = "electrotonic") currents of frog's nerve, 

 produced by polarising currents of increasing strength, from 0"i to 0"6 volt. At 

 each strength the A. and K. currents are taken twice. Their magnitude may be 

 approximately estimated by reference to the standard deflection of O"00i volt re- 

 corded at the commencement of the observation. 



current in one direction (to the right), there is a well 

 marked anodic extrapolar current (to the right). On 

 closure of the polarising current in the opposite 

 direction (to the left), there is a much smaller kathodic 

 extrapolar current to the left. 



These two core-models reproduce to us what we 

 shall find to be the rule in the case of the nerves of 



