RELATION OF ELECTROTOiS'US TO EXCITEMENT. 139 



may be induced by repeated separate irritations, for 

 instance, by inductive shocks, or by frequently and 

 repeatedly closing and opening a current. It thus 

 appears that variable currents are better adapted 

 for effecting the excitement of a nerve than are con- 

 stant currents. Inductive currents, though their dm'a- 

 tion is extremely short, may be regarded as similar to 

 constant currents which are re-opened immediately 

 after being closed. True pulsations may indeed be un- 

 failingly elicited, even with constant cinrrents, if, by 

 using suitable apparatus, they are but momentarily 

 closed, and are then again reopened. But experience 

 of the law of pulsations shows that either the closing 

 or the opening are under certain circumstances alone 

 sufficient to elicit pulsations. As we know that the 

 altered condition called electrotonus is produced in the 

 nerve by closing the current, and that on the opening 

 of the current this condition gives place, if not im- 

 mediately, yet after a short time, to the natural con- 

 dition, we may, therefore, assume that the excitement 

 of the nerve is actually due to the fact that the nerve 

 passes from a natural into an electrotonic condition, or 

 back again from this into its natural state. We may 

 suppose that the smallest particles of the nerve are 

 transferred, on the intervention of electrotonus, from 

 their normal into changed positions, and that this mo- 

 tion of the particles is under certain circumstances con- 

 nected with excitement. We have, however, found 

 that a nerve, when electrotonus intervenes, is distin- 

 guishable into two parts, the conditions of which evi- 

 dently differ ; for in the one, that of katelectrotonus, 

 the excitement is increased, while in the other, that 

 of anelectrotonus, it is decreased. It might, therefore, 



