385 



imbibed with a conducting liquid, and the phenomenon has heen 

 studied in its generality by other physicists ; but the purpose of the 

 present paper is to determine the conditions of the secondary electro- 

 motor power of nerves, in order to make a due application of these 

 conditions to the explanation of the phenomena exhibited by nerves 

 on the opening of a voltaic circuit which has traversed them. 



Having explained the object of his memoir, the author, before giving 

 an account of his experiments, proceeds to describe certain improve- 

 ments he has lately made in the instruments he employs for electro- 

 physiological researches, whereby he is able more easily and effec- 

 tually to avoid the risk of disturbing currents liable to be produced 

 in the apparatus itself. 



The fundamental experiment on which the main position of the 

 memoir rests is performed as follows : The sciatic nerve taken from 

 a frog, a fowl, or some other recently killed animal, is used for the 

 purpose. The operator first assures himself that no sign of current 

 is manifested on simultaneously touching with the galvanometer two 

 points of the nerve equidistant from its cut extremities. The dis- 

 turbing effect of the electric current naturally generated in nerves 

 may also be eliminated by placing two nerves, or two portions of 

 nerve, in such relative position that their natural currents shall be 

 opposed in direction and mutually neutralize their effects on the 

 galvanometer. To the nerve or piece of nerve thus tested are applied, 

 at some distance from its extremities, the electrodes of a pile of eight 

 or ten elements, and the exciting or pile-current is allowed for a 

 short time to pass along the included part of the nerve. When 

 the nerve is now put in communication with the galvanometer, the 

 needle deviates, and indicates that the nerve is traversed, in the por- 

 tion which had been included between the electrodes of the pile, by a 

 current the direction of which is opposite to that of the current of 

 the pile, and which lasts for a certain time. Signs of secondary 

 current are also obtained by applying the galvanometer to the parts 

 of the nerve which have not been traversed by the pile-current, that 

 is, the end-parts between the extremities of the nerve and the points 

 touched by the electrodes of the pile ; but the secondary currents in 

 these end-portions of the nerve are in the same direction as the 

 pile-current, and therefore opposed to that of the secondary current 

 developed in the part included between the electrodes and traversed 



