210 ELECTRO-PHYSIOLOGY CHAP. 



But, as we shall see later, the sustained contraction appearing 

 under these conditions in the anodic half of the muscle is really 

 a manifestation sui generis, and does not stand in any causative 

 connection with the normal persistent kathodic closure contraction 

 at the ends of fibres. With regard to the localisation of the 

 break excitation, we must further remark that it takes effect at 

 the anode in exactly the same way as the make excitation 

 at the kathode, since at first only the corresponding half of 

 the muscle twitches, and it is only later, when the excitation at 

 the anode has reached a certain magnitude, that the wave of con- 

 traction propagates itself through the entire muscle, and this with 

 a perceptible decrement, expressed in the different height of 

 twitch in either half. The 'persistent opening contraction is 

 similarly localised in the region surrounding the point where the 

 current enters. 



With the exception of the persistent closure contraction on 

 the side of the anode, occurring as described under certain con- 

 ditions only, it cannot be denied that the facts above stated are 

 collectively much in favour of v. Bezold's view of a polar excitation 

 of muscle by the current. Notwithstanding this, however, the 

 localisation of the closing and opening persistent contraction 

 cannot be taken per se as a strong proof of its validity. For if 

 the persistent closure contraction seems to be localised in the 

 region round the point of exit of the current, the objection may 

 be, and actually has been, made (Briicke, 23), that the current 

 has an excitatory action upon the whole tract, taking further 

 into consideration that this direct excitation in the region of 

 the anode soon becomes ineffective in consequence of a depression 

 of excitability proceeding from the same region. Against this, 

 again, there is the extraordinarily limited diffusion of the persist- 

 ent kathodic closure contraction, as is readily ascertained from mere 

 inspection. It appears desirable to collect more evidence, 

 and in particular to determine positively the fact that at each 

 closing twitch a wave of contraction proceeds from the kathode, 

 at each opening twitch from the anode. Here, again, the method 

 of clamping the muscle by its centre, as described above, affords 

 excellent experimental possibilities. 



Before entering more minutely into the question it will be as 

 well to determine the fundamental point of what is to be under- 

 stood in the electrical excitation of a muscle ~by kathode and anode. 



