116 THE NATURE OF THE 



may now be placed side by side with these agents ; it differs from 

 them only apparently, since its disappearance only excites when 

 accompanied by a reappearance of the stimulus. Nerve behaves to 

 a current in some respects like an elastic body ; it is not merely 

 disturbed from its equilibrium on closure, but on opening- overshoots 

 its position of equilibrium in returning, before finally coming to 

 rest. It is in this sense that I understand the almost prophetic 

 sayings of Volta and Bitter in connection with this subject. 



Volta 1 imagined that on breaking the conducting circuit an 

 obstacle is suddenly presented to the electric current, against which 

 it strikes, and rebounding gives rise to a wave in the opposite 

 direction. Bitter 2 , on the other hand, said that the make-stimulus 

 is imparted to us, while we ourselves impart the break-stimulus. 

 Bitter's words are : ' We have said that the phenomena occurring 

 on opening the circuit of a galvanic battery form a subject of 

 particular importance. We have now to justify this statement, 

 and do so by drawing attention to the great fact that these 

 phenomena occur at the moment when the organic body and its 

 parts are withdrawn from the influence of the battery. They can 

 in no way however be due to a direct action of the battery; for 

 how could the battery produce such an effect when it is no longer 

 present ? The organism which was in its circuit must itself pro- 

 duce the effect, and can only do so in virtue of having been in 

 the circuit, for apart from this there would have been no effect 

 produced.' If Pfliiger concludes from these words that ' Bitter 

 imagined that a special state produced by the current disappears, 

 which disappearance is accompanied by a contraction, as is every 

 disturbance of the internal equilibrium of the nerye,' I cannot infer 

 the same from Bitter's words ; for on the disappearance of the 

 current there might just as well reappear a state which had been 

 kept in abeyance by the passage of the current, and act as a 

 stimulus in reappearing. 



Hermann goes on to make the further objection : ' But what 

 seems to me more important is, that if we accept this conception 

 we abandon the advance of most importance embodied in Pfliiger's 

 law, the acknowledgment, namely, that the excitation is due, not 

 to the current itself, but to a definite change of state produced 

 by it in the nerve-electrotonus, as expressly stated in Pfliiger's 

 enunciation.' 



1 Du Bois-Reymond, Untersuchungen iiber thierische Elektricitat, Bd. i. p. 314. 



2 Gilbert's Annalen, 1801, xxiii. p. 30, quoted by Pfliiger, Elektrotonus, p. 74. 



