ON THE INTERNAL POLARISATION OF NERVES. 81 



vanometer was acted on when the circuit was open, the deflec- 

 tion even with 3 Meidingers and 20,000 rheochord units, did not 

 exceed $ or at most -3 divisions of the scale. With 3 Mei- 

 dingers and 10,000 units it was from -i to -2 div. ; with 4000 

 rheochord units only ! div.; with 2000 no effect could be per- 

 ceived. The errors which could possibly arise from this source lie 

 therefore almost entirely within the common limits of errors of 

 observation, as an examination of the experimental results shows. 



As electrodes I used in most instances the large unpolarisable 

 ones of du Bois-Reymond. 



The polarising current was determined by means of a ' damped ' 

 and a periodic galvanometer. The distance of the telescope from 

 the mirror of the instrument was 4400 mm . 



To obtain a greater strength of current I used for every experi- 

 ment the two sciatic nerves of a frog (rana temporaries) placed side 

 by side. In all the experiments a battery of 3 Meidinger's ele- 

 ments was employed. 



The experiments were conducted in the following way : 



The nerves are prepared and laid on the electrodes, while the 

 key K is raised and the current thus shut off from the nerve. The 

 ' nerve current ' is compensated as exactly as possible. This done, 

 and the Morse being depressed at d, the key K is closed. At a 

 given moment the Morse is let go, and the spring now presses the 

 arm t against a so as to close the polarising current. After the 

 polarising current has acted on the nerve for a given time, the arm 

 t 2 is pressed against b so as to break the polarising current, and the 

 polarisation current passes through the galvanometer. 



To determine the time during which the polarising current 

 flowed through the nerve I employed a metronome beating half 

 seconds. After a few experiments I had got sufficient practice to 

 carry out the necessary manipulations with the Morse ; the follow- 

 ing experiments may be cited as examples. 



Experiment I. 3 Meidingers, 1000 rheochord units ; duration of 

 closure of current 5" ; distance between the electrodes 1 1 mm . 



Mean 2-32 



Mean variation '1. 



