ELECTRICAL BREAK-EXCITATION. 121 



stimulation, according- to Hermann, would again occur at the 

 anode, which however is now furthest from the muscle. In this 

 case the excitation, which may be made of the same strength as in 

 the previous case, has now likewise an anodic (intrapolar) tract to 

 traverse, but soon reaches the catelectronic region, which it does 

 not again leave, even when it has passed the neighbourhood of the 

 cathode. This excitation would therefore reach the muscle, not 

 diminished, but increased in intensity; for it follows from the 

 earlier, but particularly from the exceedingly valuable recent re- 

 rearches of Tigerstedt, that an excitation always increases in 

 intensity in passing the cathode or the catelectro tonic region of 

 a nerve. With a descending current therefore the excitation at 

 the anode would reach the muscle reinforced, with ascending 

 currents it would do so diminished in strength. In other words, 

 the imperfect break-contraction would appear in the case of a 

 descending current with a small fall of current-strength : with 

 ascending currents, on the other hand, only with a much larger 

 fall ; for the former weak excitation would be reinforced in passing 

 the cathode, while the latter stronger one would be weakened in 

 passing along an anodic tract. 



But we see that exactly the opposite actually occurs of what 

 would occur if Hermann's theory were true. Ascending currents 

 have only to be slightly, but descending currents very greatly 

 diminished in strength to produce an imperfect break-contraction. 

 This result is readily intelligible according to our theory ; for the 

 conditions for an imperfect break-contraction are nearly the same 

 as for a complete break-contraction. That is to say, a reversal of 

 the current occurs, and at opening of descending exciting currents 

 the anode of the polarisation after-current intervenes between the 

 point of stimulation and the muscle, while at opening of ascending 

 exciting currents the cathode (at which excitation occurs in every 

 case) of the polarisation after-current is next the nerve. 



Hermann 1 will no doubt object to my argument that he can 

 explain all the above results by means of his theory of polarisation 

 increment. For at opening of ascending currents the excitation 

 would occur at the anode and pass to less positive parts of the 

 nerve, while at opening of descending currents the excitation, 

 starting likewise from a point whose polarisation is strongly 

 positive, would pass into parts negatively polarised. In the first 



1 See Hermann, Handbuch der Physiologic, ii. part i. p. 165, and Pflliger's Archiv, 

 vi. p. 359. 



