ix ELECTRICAL EXCITATION OF NERVE 155 



strength of current, the action of a single isolated pole. It is 

 clear that if one pole be applied as close to the nerve as possible, 

 while the broad surface of the other rests upon any distant 

 (indifferent) part of the 

 body, the density of the 



current must be unequal X/^ ZZZI_ 



at the physiological anode (iT~^c^ ^ * ^ "#) a) 



and kathode of the nerve, 

 but by no means to such 



an extent that the One p IG . 157. Schema of current distribution in a nerve in 



pole alone is involved in situ ' kk > virtual kathodes ; . virtual anodes - 



(Bernstein.) 



respect of physiological 



action. This might occasionally be the case with minimal 

 currents, but with even a low increase of current intensity 

 the action of the other pole must come into play. Every 

 nerve that has an anode must have a kathode also, even 

 if only one electrode is directly connected with it, and it 

 depends on the ratio of density between the two poles 

 whether one or the other acts alone or preponderatingly. 

 This agrees with the fact that the make twitch (" anodic closure 

 twitch " of the pathologist) is observed in monopolar excitation 

 of a motor nerve with the anode as well as with the kathode. 

 The widespread opinion among pathologists (e.g. Brenner, 27) that 

 the results of monopolar excitation of nerve may, theoretically, 

 be set side by side with the facts of ordinary bipolar excitation, 

 and the recent acceptance of this view by some physiologists 

 (Jofe, 28), cannot be admitted for the study of electrical excita- 

 tion of nerve, although the monopolar method may legitimately 

 be applied in single cases. The above theory would undoubtedly 

 lead, as in the case of Jofe, to false conclusions, con- 

 tradicted by the many facts and experiments underlying the 

 established principles of electro-physiology, which must be the 

 substrate of all future discoveries. We must therefore set aside 

 all attempts to demonstrate the law of contraction in man and in 

 intact animals, since no new points of view can be elicited from 

 them. 



IV. EXCITING EFFICIENCY OF ELECTRICAL CURRENTS 



It is evident that the phenomena underlying Pfliiger's law of 

 contraction must be more or less altered by local or general 



