PRESENT STATE OF ORGANIC ELECTRICITY. 335 



which in a motor cord induces muscular contraction ; and in 

 a sensory, comniDU or special, sensation. In order, therefore, 

 to determine the nature of the change which occurs during 

 the functional phase of a nerve, Du Bois lieymoud had recourse 

 to electric excitement 



It has already been stated that a nerve is thrown into what 

 has been called the electrotonic condition as long as a con- 

 tinuous electric current passes through a portion of it. Xow, 

 as mnscular contraction is induced at the closing and opening 

 of the circuit, and at the movements of variation in the density 

 of the exciting current, and as sensation also occurs most 

 vividly under similar conditions, it was necessary to examine 

 the electrotonic state, as produced by variable or intermitting 

 currents. For, as a variable or alternating electrotonic state 

 promised the greatest resemblance to a state of continuous 

 functional activity, its investigation might be expected to 

 throw some light on the change which takes place in the 

 ordinar}' electric condition of a nerve when it is thrown into 

 action. 



Du Bois Eeymond found that the galvanometer as distinctly 

 indicated positive and negative variations in the currents which 

 passed through it, when these currents were derived from the 

 extremities of a segment of nerve which was in an intennit- 

 ting, as when it was in a continuou.s, electrotonic state. "When, 

 however, the interruptions of the exciting primary current 

 become very frequent, the negative variation of the derived 

 currents becomes more marked, and even the positive varia- 

 tion, diminishes. It appeared probable, therefore, that by pro- 

 ducing the electrotonic state of tlie nerve by rapidly alternat- 

 ing currents, the negative condition already indicated might 

 be increased It was consequently found that if, after the 

 needle had come to rest in the deflection by the ordinar}- 

 nerve-current from either end of the segment, a rapid series of 

 alternating currents be transmitted through a portion of the 



