iv ELECTROMOTIVE ACTION IN MUSCLE 447 



the stronger. With very strong currents and long closure, the 

 negative kathodic polarisation may become as strong as the 

 equally abterminal muscle current which shows itself the 

 electrodes being unaltered on killing the end of the muscle. 

 Induction currents, too, give negative kathodic polarisation, but it^ 

 is essentially weaker than the positive anodic polarisation pm- 

 duced by the same strength of current on the same muscle 

 (sartorius). The conclusion therefore is that with growing strength 

 and duration of the exciting current, the kathodic region of the 

 muscle (physiological kathode) becomes increasingly more negative 

 in comparison with the centre. If this were an equivalent 

 phenomenon to those of physical, internal polarisation, the nega- 

 tive polarisation current would as has been shown necessarily 

 appear in approximately equal proportions on leading off from any 

 point of the interpolar tract, and this, as Hering shows, never is 

 the case. When the two galvanometer electrodes are placed 

 at the margin between the upper and middle third of the sartorius, 

 the exciting current being led in as before through the bones, no 

 polarisation current can be observed, or it is so insignificant as 

 compared with the anodic and kathodic polarisation that it may 

 practically be neglected. The relatively weak effects in the inter- 

 polar tract on the application of very strong currents, with 

 prolonged closure, are sufficiently explained by the fact that the 

 polar points of the muscle are never limited exclusively to its 

 ends, due inter alia to the fact that the sartorius not infre- 

 quently exhibits short fibres which end, or begin, somewhere in 

 the length of the muscle. On the other hand, the appearance 

 of persistent opening and closure contraction of course produces 

 inequalities in the individual parts of the interpolar region. 

 There is thus no reason for assuming internal polarisation of the 

 muscle-substance in du Bois-Eeymond's sense. All the phenomena 

 of negative kathodic polarisation can be referred to chemical altera- 

 tion (excitation, or local fatigue) in the kathodic points of the fibres 

 collectively. 



Nor are the later experiments of du Bois-Eeymond more 

 convincing, in which the application of a current of ten Grove 

 cells to the curarised sartorius, produces after 1525 minutes' 

 closure " a secondary electromotive force in the reverse direction 

 to the polarising current in every tract of the muscle," its magni- 

 tude increasing with the length of the tract led off. For the 



