THE PHYSIOLOGICAL ACTION OF THE ELECTRIC CURRENT. 489 
during contraction. The conclusions which we have drawn are very general : the 
excitability of a nerve is modified by the electric current according to its direction ; and 
when we reflect that the passage of the inverse electric current through the nerve of 
an animal deprived of life, prolonged for two or three hours, produces on ceasing a very 
violent and persisting contraction, and that when this happens it has re-acquired the 
property, which it had lost before, of provoking contraction at the moment the inverse 
current begins to be passed, and that finally the passage of the direct current, for a 
time relatively very short, entirely destroys the excitability of the nerve, we are led to 
believe that the action of the current upon the excitability of the nerve is opposite for op- 
posite directions. This is the point I wished to establish by experiments of measure, 
and I hope that I have satisfactorily demonstrated the fact. I began by measuring 
the contraction with Breguet’s apparatus, which I have described. It was important 
to determine and compare the contractions excited by the direct and by the inverse 
currents*, principally taking into account the duration of the passage of the current. 
In all these experiments the same nerve must never be submitted to the action of 
both the direct and the inverse currents. My mode of operating is this. I prepare 
the frog in the ordinary manner, and after having divided the pelvis from the rest of 
the trunk, I separate it into two parts, so that the two limbs remain united by the 
lumbar nerves attached to a portion of spinal marrow. I fix this piece of the spinal 
cord in the vice, and in this manner I am enabled to pass the current in either nerve 
ad libitum. By repeating a great number of experiments, sometimes beginning with 
the direct, at other times with the inverse current, it is not difficult to obtain a table 
of numbers which agree with one another as well as could be expected in this kind 
of experiment. I always leave the circuit open as short a time as possible between 
one experiment and another. A certain degree of practice enables the experimenter 
to employ only as short a time as two seconds in bringing the ivory index back into 
position. In the same way the shortest possible time for leaving the circuit closed 
is two seconds, for this is exactly the same time required for replacing the needle 
which had been removed from its position by the first contraction. The numbers 
which follow are the degrees of the division of the dial of the apparatus. It is un- 
necessary for me to give all the numbers resulting from my experiments; it will be 
sufficient to cite some of them in order to show the course of the phenomena. The 
following experiment proves the weakening of the excitability of the nerve owing to 
the passage of the direct current. Each passage of the current was prolonged for 
sixty seconds, and the following numbers give the measure of the contraction ob- 
tained each time the circuit was closed. These numbers are 16, 12, 10, 8, 4, 2, 2, 1. 
The inverse current was next tried on the other limb. On prolonging the passage of 
the current for two seconds I obtained a contraction of 10°. I left the circuit closed 
for sixty minutes, and still the contraction was 7 on opening the circuit. Thus far 
these numbers merely show the principal fact upon which I have insisted so strongly, 
* Both at the commencement of the current and on its ceasing. 
3 s 
MDCCCXLVI. 
