PHENOMENA OF MUSCLE AND NEEVE. 321 



CM I A 



Polarisation after-currents 



(of short duration) 



p 7 ' 7 7 7 



Action after-currents in nerve ... **- 



(of long duration) a a a' 



Action after-currents in muscle ... * * 



a a" 



It lies in the nature of the excitation after-current that it should 

 be much more prolonged than the polarisation after-current, which 

 as well in the tissues as in the conducting axis schema, in all cases 

 rapidly disappears. Nothing is more natural therefore than that 

 the conflict of the two currents should express itself in the double 

 character of the after-currents actually observed, the first phase of 

 which always indicates the polarisation, the second the action- 

 current. Further, the more the action-current is developed in 

 comparison with the polarisation-current, the more will the first 

 phase of the doubly-directed current tend to disappear, as also 

 must be the case when the magnet has a slow swing. 



We have therefore to expect that 



(1) The intrapolar region should show an after-current which is 

 first (opposed to the polarising-current), and then + : 



(2) The anodal extrapolar region an after-current first + and 

 then : 



(3) The kathodal extrapolar region an after-current which is 

 always + . 



Now the relations established by experiment agree in all points 

 with these. That given above under i is the' actual condition as 

 stated in du Bois-Reymond's treatise, those given under 2 and 3 

 were stated previously by myself and A. Fick, and are fully estab- 

 lished by the present investigations. 



It is further readily intelligible that the intrapolar action- 

 current, du Bois-Reymond's second positive phase, should only 

 appear after currents which are strong and of short duration ; 

 strong, because only then is the breaking excitation sufficiently 

 prolonged to overlap the polarisation after- current, and of short 

 duration, because the latter current is not so markedly developed by 

 short as it is by long closure, and thus the complete concealment of 

 the action-current by the polarisation is not so easily produced. 



Further proof of the correctness of my explanation is furnished 

 by the circumstance discovered by du Bois-Reymond himself, that 

 his positive phase, our current of action, is intimately connected 



Y 



