x ELECTROMOTIVE ACTION IN NERVE 295 



on the preservation of normal structural conditions in the nerve, 

 but also, fundamentally, upon its conductivity. 



Moreover, it can be shown that at a time when no trace of 

 electrotonic action is demonstrable during ether narcosis at a 

 distance from the exciting tract, there are strong and regular 

 electrotonic currents in its immediate vicinity, and the reaction 

 of these under prolonged etherisation is of great interest. 



Normally there is without exception a marked difference in 

 the strength of electromotive action on the side of the anode and 

 of the kathode respectively, which is most distinct under the 

 action of weak and medium battery currents. It follows that 

 katelectrotonic deflections often fail altogether, or appear only as 

 a trace at a distance from the exciting tract, while on reversing 

 the current auelectrotoiius may appear in its full strength, other 

 conditions being uniform. Even in the vicinity of the exciting 

 tract the difference between kat- and anelectrotonic deflections is 

 considerable, the latter being often more than double. 



This reaction is completely altered with progressive etherisation, 

 i.e. the anelectrotonic deflections rapidly diminish at uniform excita- 

 tion, while the katelectrotonic effect remains at first unaltered, or may 

 even increase slightly. Subsequently there is always a point at which 

 the kat- and anelectrotonic defiections are completely equalised, in 

 respect of magnitude as well as of time-distribution, and this persists 

 whatever the strength of current. It should also be remarked that 

 with increasing current intensity the increment of deflection is 

 approximately proportional in the later stages of ether narcosis. 

 If the narcosis is sufficiently protracted, the katelectrotonic effect 

 will also be modified in course of time (as would be anticipated), 

 but the increasing diminution of the deflections will then keep 

 pace with the simultaneous diminution of arielectrotonus. 



If the narcosis is interrupted only when all trace of electro- 

 tonic action has disappeared, there is no recovery of the normal 

 vital properties of the nerve ; it is then, anatomically and 

 physiologically, dead the medullary sheath of the single fibres 

 exhibiting the familiar clefts by which dead nerve is characterised. 

 But if the preparation is removed earlier directly after the 

 heterodromous electrotonic deflections have been equalised from 

 the action of the ether, and placed in a moist chamber, recovery 

 will at once set in, as evidenced by a rapid increase in f/ir 

 magnitude of the anelectrotonic deflections, with constancy of 



