ix ELECTRICAL EXCITATION OF NERVE 149 



conductivity, which long outlasts the opening of the polarising 

 circuit (local fatigue). Eutherford (24) indeed has shown, with 

 weaker polarising currents and shorter closures, that conductivity 

 is retarded in anelectrotonus only, while it is accelerated in kat- 

 electrotonus ; it is only with strong currents or longer closure 

 that such acceleration passes into its contrary. It had previously 

 been pointed out by Hermann (25) and Griinhagen (25), and also 

 by Werigo (25), that with longer closure of strong currents the 

 initially augmented excitability of the kathodic points of the nerve 

 gave way to a gradually developing inexcitability, which may 

 amount to complete impenetrability to excitation with even the 

 strongest induction shocks. This state develops in the muscle 

 proportionately with the strength of the polarising current, 

 and may make such a rapid intra- and extra -polar entrance 

 that it is hardly possible to demonstrate the transitory rise 

 of excitability. With weak currents, on the other hand, it is 

 hours before this secondary alteration in excitability makes 

 its appearance. If the polarising current is opened at the 

 moment at which the kathode becomes impenetrable, excitability 

 (conductivity) returns almost instantaneously^to disappear again 

 with renewed closure of the current. V. Bezold attempted to 

 draw conclusions as to conductivity within the intrapolar tract 

 itself, and assumed an indifferent point, halving the area traversed 

 by the current (its position being independent of strength of 

 current), from either side of which conductivity diminished 

 regularly towards both poles. 



In immediate connection with these changes in the excitability 

 of nerve during the electrotonic state, and its direct after-effects/ 

 there is a whole series of excitatory and inhibitory phenomena 

 which must be briefly considered. The opening excitation was 

 referred to above as an after-effect of the passage of current, 

 in Eitter's sense, i.e. a reaction of the nerve to certain alterations 

 produced by the current. Eitter expresses himself character- 

 istically as follows (Beitrage zur naheren Kenntniss des Galvanismus, 

 i. p. 78 ff, 1802): "We have stated that the phenomena which 

 accompany the removal of battery - currents are of peculiar 

 significance. In justification of this assumption we need only 

 emphasise the fact that they appear at the instant in which 

 the organic body and its constituents are withdrawn from the 

 influence of the battery. Hence they are in no way the im- 



