I'l'l PHYSIOLOGY OF MUSCLES AM> NKIIY! -. 



in tension and the dinner in excitability both probably 

 depend on molecular changes within the nerve, as to 

 the nature of which we are not yet in a portion to say 

 anything further, but the simultaneous appearance of 

 which, under the influence of externally applied electric 

 currents, is nevertheless \ery interesting and will per- 

 haps in future afford a key to the nervous processes 

 which occur during- excitement. 



In examining- the changes in tension which take 

 place during electrotonus, the differences in tension 

 already existing at the various points must of course 

 be taken into consideration. ]f the diverting arch is 

 applied to two symmetrical points of the nerve, thev 

 are homogeneous. If it is applied to any other points. 

 the existing differences in tension can be cancelled l>v 

 the method of compensation above described (chap. x. 

 4). The differences in tension due to electrotonns 

 are then seen unmixed. In all other cases these dif- 

 ferences express themselves in the form of an increase 

 or decrease in the strength of the nerve-current which 

 happens to be present. Yet the law of the changes 

 in tension is the same in all cases. 



6. As we found certain points of resemblance be- 

 tween nerves and glands, so the ner\e< of the tissue of 

 the electric organs, in which in the cases of the tishes 

 already mentioned such powerful electric action takes 

 place, may he classed with these. Without entering 

 deeply into the researches, as yet very incomplete, 

 which have Keen made into the structure of tlioe 

 electric organs, we may yet accept as already pr\ ,-d 

 that the so-called cln-lrir jil<ite a delicate membran- 

 ous structure. \ery many of \\hich, arranged side bv 

 >ide and under one another in regular order, constitute 



