492 PROFESSOR MATTE UCCl’S ELECTRO-PHYSIOLOGICAL RESEARCHES. 
studied these phenomena anew, measuring the contractions in a frog subjected for 
some minutes to the passage of the direct current : the contraction, which was 20° at 
the commencement of the experiment, was but 8° at its conclusion on closing the 
circuit, and 0° on breaking it. The interval of time that the circuit remained 
open was a little less than two seconds, that is to say, the shortest time for the ex- 
periment; in the same manner the circuit was left broken the shortest time possible. 
I next varied the time of the circuit remaining incomplete. The following are the 
results obtained: for two seconds of repose, 10°; for three seconds, 11°; for five 
seconds, 12°; for ten seconds, 12°. Where the nerve has lost still more of its excita- 
bility, the effect of the repose is protracted still longer. Upon a frog, the nerves of 
which had been traversed by the direct current during thirty minutes, 2° of con- 
traction followed upon breaking the circuit and again closing it immediately. After 
two seconds of repose, the contraction was 6° ; after three seconds, 6° ; after fifteen 
seconds, 7° ; after thirty seconds, 8°. The time, therefore — always very short — that 
the nerve is left unacted upon by the current, and in which it acquires all the excita- 
bility which it is capable of regaining, is so much the shorter as its excitability is 
greater. I must add, that the increase of excitability produced by the repose of a 
nerve which has been stimulated by the direct current, persists in this same nerve 
for a time admitting of being measured, even after it has been again subjected to the 
passage of the direct current. There were 2° of contraction on closing the direct 
circuit, which had already been closed for thirty minutes. Leaving the circuit open 
for fifteen seconds, then closing it, the contraction was 8° ; then closing the circuit 
immediately, and leaving it closed as short a time as possible, I opened and again 
closed as quickly as possible, and the contraction was 6°. Proceeding in the same 
manner, and passing the direct current for four seconds, the contraction was 3°, for 
five seconds only 2°, as at the commencement. A very short time of repose is suf- 
ficient to restore to the nerve as much as it can regain of that excitability which it 
had lost by the passage of the direct current ; in like manner a very short time of 
the passage of this current will dissipate the increase of excitability acquired by 
repose. In general, the duration of these actions is in the inverse ratio of the degree 
of excitability of the nerve. 
We now pass on to those experiments which prove incontestably that the excita- 
bility of the nerve is increased by the passage of the inverse current , and that , within 
certain limits , proportionally to the duration of the passage of this current. After 
having arranged a frog in my apparatus, I pass a direct current through the lumbar 
nerve for thirty minutes ; I then wait until all contraction from the passage of the 
direct current has ceased, and that even after having left the nerve in repose for 
thirty seconds or sixty seconds. I then pass the inverse current, which scarcely ever 
occasions any contraction on closing the circuit, but on leaving the circuit closed for 
a longer or shorter time, there are different degrees of contraction on breaking the 
circuit. The following are some of the numbers obtained. In one case, after passing 
