THEORY OF THE BREAK-CONTRACTION. 



65 



short, we have now to examine whether, in reality, all the facts 

 we find when the current is broken are really in accordance with 

 those which present themselves when it is closed. 



Just as the polarising current produces its exciting effect on 

 closure at the negative pole, so the seat of stimulation at break is 

 at the positive pole, which now becomes the negative pole of the 

 polarisation-current. 



And, just as the positive pole of the polarising current exerts a 

 blocking action, so at break there is a tendency to blocking at the 

 negative pole, for this is now the positive pole of the polarisation- 

 current. Starting from this, we can with the greatest ease establish 

 theoretically the law of contraction. 



Most physiologists of the present day are agreed in expressing 

 the law of contraction in its most general form after Pfliiger's well- 

 known scheme. 



LAW OF CONTRACTION 1 . 



If my interpretation of the make-contraction is correct, the same 

 phenomena must occur when a descending current is broken as 

 when an ascending current is closed, and, conversely, we shall 

 encounter the same phenomena when an ascending current is 

 broken as when a descending current is closed. The first stage 

 of Pfliiger's law will be the only exception, as the current has 

 not yet attained the intensity required to produce polarisation 

 of sufficient strength. The following scheme offers a survey of 

 these relations, the first stage being omitted for reasons already 

 given. 



1 Pfliiger, Untersuchungen iiber die Physiologic des Electrotonus, Berlin, 1859, 

 p. 454. 



F 



