1. Introduction. 



1 IN the investigation of the secondary electro-motive phenomena 

 in the adductor muscle of Anodonta 2 , the most striking- fact seemed, 

 that here, quite contrary to the usual behaviour of the striated 

 trunk muscles of the frog, not only positive anodic but also positive 

 kathodic polarisation is observed, for on leading off from the anodic 

 as well as from the kathodic half of the muscle traversed by the 

 current longitudinally, occasionally an after-current of the same 

 direction and frequently of very considerable strength appears, 

 without simultaneous internal polarisation of the intrapolar tract 

 of any importance at all. Hence, the inference is, that the cause 

 of this phenomenon is to be sought solely in alterations of the 

 substance of the muscle produced by the polarising current at its 

 points of exit. 



The anodic persistent excitation which follows on opening a 

 current of corresponding intensity and duration of closing, explains 

 positive anodic polarisation in a thoroughly satisfactory manner, as 

 has been convincingly shown in investigations already published 3 , 

 whilst the negative kathodic after-current, which, under ordinary 

 circumstances, is prominent in striated muscle, might be proved to 

 be in the main a result of the alteration of the kathodic spots of 

 fibre by the preceding closing excitation. 



It is however intrinsically more difficult to attain a definite 



1 [This paper is the eighteenth in the series of 'Contributions to the general 

 Physiology of Muscle and Nerve,' which have been published during the last six 

 years by Professors Hering and Biedermann of Prague. Ed.] 



a As I have since learnt from a copy of Professor Bernstein's Dissertation, ' De 

 animalium evertebratorum musculis nonnulla,' Berolini, 1862, which he kindly sent 

 to me, but which was unfortunately inaccessible to me at the time when I wrote my 

 work upon the adductor muscle of Anodonta, he was the first to draw attention to 

 the peculiar ' Tonus ' of this preparation, and he had investigated its electromotive 

 actions also before Fick. 



3 See No. VII and No. IX of this work. Also Hering, ' Uber Veranderungen 

 der Muskeln,' &c. Sitzungsber, vol. Ixxxviii. p. 415. 



