356 



all in which the action of the galvanic current upon the nerve gives 

 rise to the " voltaic alternatives") is inverse. In these last moments 

 the nerve-current in these nerves may be sometimes direct, some- 

 times inverse, and this change of direction may take place more 

 than once ; but except in these last moments, the author finds the 

 direction of the nerve- current to be invariably inverse. 



Fig. 5. 



The second fact is furnished by Professor du Bois-Reymond in an 

 experiment in which the two ends of a long portion of nerve are 

 placed upon the cushions of two galvanometers, and the middle of 

 the nerve is laid across the poles of a galvanic apparatus. Looking 

 at the needles of the galvanometers before passing the galvanic cur- 

 rent, they are seen to diverge under the action of the nerve-current ; 

 and from the direction of the divergence, it is evident that this cur- 

 rent passes from the end to the side of the nerve. Looking at the 

 needles while the galvanic current is passing, one needle is found to 

 move still further from zero, the other is found to return towards 

 zero. Let A B be the nerve ; let the arrows a a' and b b' be the 

 nerve-currents included between the cushions a a f and b V of two 

 galvanometers ; and let the arrow P N be the current between the 

 poles P N of the galvanic apparatus ; and under this arrangement 

 the needle of the galvanometer will recede, and show increase of cur- 

 Fig. 6. 



rent (-}-) at the end B, where the nerve-current and galvanic current 

 coincide in their direction ; and at the end A, where the two currents, 

 natural and artificial, do not coincide in their direction, the needle 

 of the galvanometer will go back, and show decrease of nerve- 

 current ( ). 



The third fact, which has been recently furnished by Professor 



