220 



niYSIOLOGY OF MUSCLES AND NERVES. 



can be expected in experiments of this nature ; and it 

 may be unconditionally inferred from this correspond- 

 ence that negative variation and excitement in the nerves 

 are two intimately connected and inseparable processes, 

 or rather two aspects of the same process observed by 

 different means.^ 



5. The negative variation of the nerve current is 

 not the only electric change known to occur in nerves. 

 Under the name ' Electrotonus ' we have already (ch. 

 viii. § 1, p. 125) mentioned certain changes in the ex- 

 citability which occur in the nerve fibre as soon as an 



Fig. 60. The changes in texsiox during electrotoxls. 



electric current is transmitted through a part of it. 

 These changes in the excitability correspond with 

 changes in the electric condition of nerves, which we 

 called electrotonic. In fig. 60, oi n' represents a nerve, 

 a and k two wires applied to the nerve through which an 

 electric current is transmitted from a toward Z-; a is 

 therefore the anode, h the kathode of the current em- 

 ployed for the generation of electrotonus. As soon as 

 this current is closed, all the points of the nerve on the 

 side of the anode (from n to a) became more positive, 

 all on the side of the kathode (from h to n) more 



' See Notes and Additions, No. 12. 



