278 THE SO-CALLED SECONDARY ELECTROMOTIVE. 



If a current is allowed to flow lengthwise through a tract of 

 muscle, nerve, or electrical organ, and immediately this is broken 

 a portion of the tract is connected with a galvanometer, ordinary 

 internal polarisation i. e. a current opposed to the one led through 

 does not always manifest itself. 



Thus, if the current led into the tissue is very strong (for the 

 thigh muscles at least that of 2 Groves, 5 Groves for the sciatic 

 nerve) and the duration of its closure is very short, an effect 

 appears which is in the same direction instead of in the opposite 

 direction ; or a double effect may show itself, which is first in the 

 opposite and then in the same direction 1 . 



This after-effect in the same direction as the polarising current is 

 connected more intimately with the living condition of the tissue 

 than the one opposed to it in direction ; moreover, its production 

 is more or less clearly favoured by a direction of current which 

 coincides with that of the natural excitation (in muscle and nerve) 

 or of the shock (in electrical organs). 



2. The Theoretical and Controversial Observations of 

 du Bois-Beymond. 



Du Bois-Reymond denotes as 'negative polarisation' the after- 

 effect found by Peltier in a led-through tract, and which is present 

 even with weak polarising currents, especially if these are of 

 long duration. There is nothing to be said against this nomen- 

 clature, except that the word * negative ' is superfluous. That the 

 phenomenon depends upon true galvanic polarisation undoubtedly 

 follows from its whole character, from its direction as compared with 

 that of the current which produces it, its rapid disappearance after 

 the break of this current, the relationship of its magnitude to that 

 of the current and to the duration of closure of the latter, and further 

 the relationship of its amount to the position of the lamina of hetero- 

 geneous substances in the tissues 2 ; a fact discovered by myself, 

 which du Bois-Reymond has omitted to refer to, although such 

 an indication is of much more value than pure speculations 



1 [For convenience of description, the after-effect in the same direction as the polar- 

 ising current, termed by our author ' gleichsinnig,' is denoted in this translation by 

 the sign + , the opposed effect, termed 'gegensinnig,' by the sign , the signs merely 

 indicating the relation of the direction of the after-effect to that of the polarising 

 current. Tr.] 



3 Sec Pfluger's ' Archiv/ vol. v. p. 232. 



