490 
PROFESSOR MATTEUCCl’S ELECTRO-PHYSIOLOGICAL RESEARCHES. 
which is, the very different rate of reduction of the excitability observable in two nerves, 
one of which is exposed to the passage of the direct, the other to that of the inverse 
current. 
It was very important to compare the excitability of a nerve subjected to the pas- 
sage either of the direct or of the inverse current, with that of a nerve left to itself 
for an equal time. The results at which I invariably arrived are these : we are sure 
when employing the direct current that there will no longer be any contraction after 
the passage of the current has been kept up for fifteen or twenty minutes. With the 
inverse current, on the contrary, we have just seen that after a much longer passage 
of the current, the contraction produced on breaking the circuit was not greatly in- 
ferior to that which takes place in a nerve quite fresh, and having experienced the 
action of the current for only two seconds. The following are the numbers given by 
one nerve left untouched, and another exposed to the inverse current. I submitted 
to experiment a nerve left to itself; and twenty-five minutes after the preparation of 
the limb I passed the inverse current for the shortest possible time, and on opening 
the circuit the contraction was 20°. The other nerve, exposed to the current for 
twenty-five minutes without intermission, gave 18° on opening the circuit. In another 
experiment the numbers were 16° and 12° for a passage of thirty-five minutes. Re- 
peating the same experiment with the direct current, I never remarked any percep- 
tible contraction on breaking the circuit and reclosing it immediately. It is just to 
observe that the natural decrease of strength, independent of the passage of the cur- 
rent, ought to be greater for the nerve subjected to the experiment, and which is 
always somewhat stretched by the weight of the limb, than for the nerve which is 
left in a state of repose. 
It is easy to prove that the passage of the inverse current in a nerve acts for a definite, 
though a very short time in producing an increase of excitability, which for the same 
reason disappears very quickly after breaking the circuit. To prove this I shall com- 
mence with an exposition of the experiments instituted for measuring the contrac- 
tion produced, as well on closing as on breaking the circuit of the inverse current. 
We know, in general, what happens in this case. In the first place, when the nerve 
is very excitable, there is contraction both on closing and breaking the circuit, and 
little by little the former contraction disappears completely. The following numbers 
were obtained on leaving the circuit closed for two seconds, and open for that time. 
At first a contraction of 20° both on closing and on breaking the circuit ; at the ex- 
piration of ten minutes there was no contraction on closing the circuit, but one of 
12° on breaking the circuit. At the end of thirty minutes things were precisely the 
same. The following are the numbers obtained from another experiment under the 
same circumstances, but upon a nerve which had already lost much of its excita- 
bility. 
