286 THE SO-CALLED SECONDARY ELECTROMOTIVE 



incompletely disappeared. I can entirely verify the fact that the 

 appearance of the + after-current, and of this only, is favoured by 

 short times of closure and by strong currents ; that, further, the 

 phenomenon is intimately connected with the vitality and, as 

 I am able to show, with the excitability of the animal-tissue. 

 By fatigue, even when produced by an ordinary tetanus, + after- 

 currents become diphasic, and diphasic ones become entirely . 

 On the other hand, the after-current, especially in a nerve, is 

 a phenomenon which, even in summer, can be demonstrated for 

 from 24 to 48 hours, feebly indeed, but quite plainly ; whilst the 

 4- after-current appears always with fresh preparations, and these 

 alone. As boiling-water, according to du Bois-Reymond, con- 

 firmed by myself, puts an end also to the after-current, possibly 

 the most correct expression of the facts would be this, the after- 

 current is associated with the maintenance of structure, the -\- with 

 that of life. Electrotonus has a certain resemblance to the after- 

 effect, inasmuch as it often shows plainly traces of its presence in 

 exhausted and long-kept nerves. 



If then the + after-effect is thus intimately connected with 

 excitability, the first question which arises is, whether it may 

 not possibly be itself an excitation phenomenon. It is incon- 

 ceivable to me how du Bois-Reymond could have overlooked this, 

 and so given himself the trouble of seeking an explanation in the 

 physics of the future. 



My first thought on reading du Bois-Reymond's communication 

 was that this + after-effect was the current of action proceeding 

 from a prolonged break-excitation. It is well known, as Pfliiger 

 discovered, that both in nerve and muscle the break of a strong 

 current is followed in the anelectrotonic tract by a violent and pro- 

 longed excitation. We may fairly assume that this excitation is 

 strongest and most prolonged at the anode itself, and decreases 

 towards the indifference point. According to the laws of action - 

 currents which I have advanced, a point near the anode must, after 

 break, be negative to one further off, and thus an intrapolar after-cur- 

 rent must be produced having the same direction as the polarising- 

 current ; as, according to Pfliiger, the indifference-point when 

 strong currents are used lies close to the kathode (at least in 

 nerve), this condition must spread throughout the entire intrapolar 

 region. 



This current is so directly necessary, and without being con- 

 nected with any theory is in itself so undoubted, that du Bois- 



