ON NERVE-EXCITATION BY THE NERVE-CURRENT. 143 



as I refrained from doing concerning the excitation of muscle, and 

 will confine myself to the suggestion Which has just been made. 



Excitation of the transverse section of a nerve ty fluids. 



Just as a muscle contracts so soon as its transverse section comes 

 in contact with a conducting fluid, so does the nerve of a sufficiently 

 excitable nerve-muscle preparation contract when the end of its 

 nerve is dipped into a conducting fluid ; and the contraction is 

 apparently simultaneous with the contact. One is inclined to 

 regard this contraction as caused merely by the sudden external 

 closure of the nerve-current, and in harmony with this view is 

 the fact that badly conducting fluids, such as alcohol, solution of 

 corrosive sublimate, Sec., do not give rise to the contraction at the 

 moment of contact. But the assumption of a simultaneous chemical 

 excitation of the nerve substance that has been laid bare by the 

 incision, and is still perhaps, to some extent, excitable, cannot, in 

 this case, be excluded in so easy and convincing a fashion as in the 

 corresponding experiment on muscle. 



As is well-known, Eckhard 1 , who was the first to carry out 

 systematic experiments relating to the excitation by fluids of 

 the transverse section of nerves, considers this excitation to be 

 exclusively chemical. He obtained no action by dipping the nerve 

 into water, bisulphide of carbon, solutions of metallic salts (with the 

 exception of nitrate of silver), organic acids such as gallic acid, and 

 volatile oils. 



The fluids which Eckhard found efficacious produced effects of 

 two kinds. The first kind of action showed itself in a contrac- 

 tion at the instant of contact, the second followed if the nerve were 

 dipped deeper, and consisted of contractions which began sooner or 

 later after immersion, spread over a greater or smaller number of 

 muscular fasciculi successively, and lasted for a very variable time, 

 according to the agent employed, &c. 



According to Eckhard the first contraction may be avoided if, 

 instead of cutting the nerve, one ties it and immerses the tied end. 

 With solutions of the fixed alcalies, provided they were not too 

 weak, Eckhard obtained regularly both the contraction immediately 

 following contact of the transverse section, and the subsequent 

 contractions ; mineral acids gave the second kind of contractions, 

 and only very rarely the first. All the other fluids which Eckhard 



1 Die chemische Eeizung der motorischen Froschnerven. Zeitschr. f. rat. Medic. 

 Neue Folge, i. p. 302, 1851. 



