222 PHYSIOLOGY OF MUSCLES AND NERVES. 



in tension and the change in excitability both probably 

 depend on molecular changes within the nerve, as to 

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

 anything further, but the simultaneous appearance of 

 which, under the influence of externally applied electric 

 currents, is nevertheless very 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. If the diverting arch is 

 applied to two symmetrical points of the nerve, they 

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

 the existing differences in tension can be cancelled by 

 the method of compensation above described (chap. x. 

 § 4). The differences in tension due to electrotonus 

 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 nerves of the tissue of 

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

 already mentioned such powerful electric action takes 

 place, may be classed with these. Without entering 

 deeply into the researches, as yet very incomplete, 

 which have been made into the structure of these 

 electric organs, we may yet accept as already proved 

 that the so-called electric plate — a delicate membran- 

 ous structure, very many of which, arranged side by 

 side and under one another in regular order, constitute 



