398 



Royal Society : — 



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 d and b b f be the 

 nerve-currents included between the cushions a a f and b b' 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. 



.7V 



V 



1 B 



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 

 Eckardt, is to be found in an experiment which may be illustrated 

 by means of the two following figures. In this experiment, the 

 nerve of a properly prepared frog's leg is placed, one portion (that 

 nearest to the leg) across the poles I I' of an induction coil, another 

 portion across the poles P N of a galvanic apparatus. Having done 

 this, the leg is first thrown into a state of tetanus by passing a series 

 of induced currents, and then (the tetanizing influence still con- 

 tinuing in operation) the continuous current of the galvanic apparatus 

 is transmitted from P to N. This is the experiment. The result 

 is that the tetanus ceases when, as in fig. 7, the inverse current 



Fig. r. 



passes, and continues when, as in fig. 8, the direct current passes. 



Fig. 8. 



I' 7T 



Nor is this result altered by inverting the order in which the con- 



