THE PHYSIOLOGICAL ACTION OF THE ELECTRIC CURRENT. 
491 
Contraction on closing the circuit. 
Contraction on breaking the circuit. 
20 
12 
4 
2 
0 
0 
id. 
20 
18 
16 
16 
12 
12 
12 
12 
12 
id. 
When the nerve is very excitable the action of the inverse current may be proved 
to be proportional to the time of its passage, making the passage in one case ex- 
cessively short. In effect, when the nerve is endowed with a very high degree of 
excitability, the contraction produced on breaking the inverse circuit, whether it be 
for one second, for twenty seconds, or even for thirty seconds, is always the same ; 
but the case is no longer the same when the current is passed for a shorter time 
than one second. Unfortunately I have not been able to employ an apparatus for 
measuring the duration of the passage of a current for a shorter time than one second. 
The way I arrive at these results is this : instead of establishing the circuit by dipping 
one of the conducting wires of the pile in the same recipient of mercury in which is 
the other wire, I hold them both in my hands and bring them rapidly in contact with 
one another. The numbers obtained from various experiments and with different frogs 
are 22°, 24°, 28° of contraction, on breaking the inverse circuit, and these numbers 
were the same whether the current w r ere passed for one second only, or as long as 
twenty seconds or thirty seconds. On touching one wire with the other very quickly, 
the contractions in the same circumstances were only 4°, 6°, 8°. 
When instead of a nerve, the excitability of which is very great, we choose for our 
experiments one in which this is considerably diminished, it is easy to prove that the 
contraction produced by the inverse current ceasing to pass increases, within certain 
limits, proportionally to the time of the passage of the current. To bring the nerve 
to this state of excitability, it may be either left to itself for a long time, or be sti- 
mulated by frequent intermitted currents in rapid succession. Before detailing the 
results which follow, it is necessary to mention what happens when a nerve has been 
exposed for a long time to the passage of the direct current, or to repeated actions 
of this current in those cases in which the nerve is left to itself. In fact, in order 
to be able to measure what is due to the action of the inverse current, we must first 
know what is the effect upon the nerve of its being left to itself, after the direct cur- 
rent has ceased to act upon it. 
Marianini had already found that a frog which has lost the faculty of contracting 
upon passing the current, re-acquires it on being left to itself for five seconds. I have 
3 s 2 
