

INTRODUCTION. 95 



Reymond in his investigations, reduce to zero the part of the nerve- 

 current led off by the electrodes, so that no current is indicated by 

 a galvanometer inserted in the nerve-circuit, through which the 

 two opposed currents pass. 



I always employed, on the contrary, far stronger exciting cur- 

 rents. If, for instance, the nerve-current was compensated in the 

 ordinary way by a derivation-circuit of 5 cm., the first break- 

 contractions began with a derivation-circuit of 10 to 20 cm. 



In this respect my experiments differ from those of Hering, who 

 employed far weaker currents and very excitable preparations. 

 Hering says that it is necessary for the success of his experiments 

 that the frog's limb employed should be excited even by closure and 

 opening of the nerve-current. In my first series of experiments I 

 never used such preparations, and in my second, referred to in a 

 preliminary communication 1 , I did not particularly study their 

 behaviour, since Hering had already thoroughly done so. 



To prevent misunderstanding, or rather to remove those which 

 have already arisen 2 , I must further explain that I do not suppose 

 that by compensating the nerve-current in the ordinary way I can 

 reduce the currents present in a nerve to zero. On the contrary, a 

 nerve, whose current is compensated in the ordinary way, behaves, 

 as Hermann has clearly explained 3 , like a nerve without any external 

 circuit. Opening of a circuit through which a current exactly com- 

 pensating the nerve- or muscle-current passes cannot, as was found 

 by Hering- and Biedermann and emphasised by Hermann, elicit any 

 excitation in the nerve or muscle, for no electric change whatever 

 is thereby occasioned in its fibres. 



But the conditions are, I think, quite different if the currents 

 used are not of the strength of ordinary compensation-currents, but 

 far stronger. In this case it is really possible, by means of so-called 

 over-compensation, to make the nerve currentless, if not in its whole 

 length, yet assuredly in a certain part. With the exceedingly com- 

 plicated conditions under consideration, it will, I think, be best to 

 consider the nerve trunk in four sections, which are affected as 

 follows by the strong counter - current. In the first, perhaps 

 smallest, section, the nerve-currents are unaltered, their lines of 

 flow differing too much from those of the counter-current for any 

 alteration to be produced. In a second section, however, the nerve- 



1 Breslauer iirztliche Zeitschrift, 1882, No. 23. 



2 Virchow's Jahresbericht iiber Physiologic, by Gad, 1882, p. 193. 



3 Pfliiger's Archiv, xxx. p. 14. 



