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XXV. Electro- Physiological Researches. — Fourth Memoir. The Physiological Action 
of the Electric Current. By Signor Carlo Matteucci, Professor in the University 
of Pisa, 8$c. &;c. Communicated by Michael Faraday, Esq., F.R.S., fyc. 8$c. 
Received June 11, — Read June 18, 1846. 
In my Treatise upon the Electro-Physiological Phenomena of Animals, at page 230 
I have described the following experiment : — “ I prepare a frog after the method 
adopted by Galvani, separating the junction of the two thigh-bones, and placing 
them so divided between two glasses, with the claws immersed in these glasses. 
Introducing the conductors of a pile of from sixty to eighty pairs in both the glasses, 
I pass a current through the frog, which is direct in one limb and inverse in the 
other. After a lapse of from fifteen to twenty minutes, I establish a communication 
between the glasses by means of a wire, whereupon the limb traversed by the inverse 
current immediately contracts. On quickly removing the communicating wire, no 
contraction whatever occurs.” I concluded from this experiment that the action of 
the electric current, in weakening or destroying the excitability of the nerve, was not 
the same whatever were its direction, and that the direct current acted with a much 
greater energy than the inverse. This fact appeared to me to be of sufficient import- 
ance to warrant further investigation, and I think that the results at which I have 
arrived will serve to throw some light upon that difficult subject, the physiological 
action of the electric current. I felt convinced, in the first place, that it now behoved 
me to employ means for the investigation of these phenomena far more exact than 
those I had hitherto resorted to. Every natural philosopher who has ever so little 
studied the contractions caused by the passage of the electric current upon the nerves 
of a frog, prepared for the purpose, must certainly have perceived how very difficult 
it is to arrive at satisfactory results, where the force of the contraction excited is to 
be judged of by the eye. In this manner our knowledge is limited to the fact, that 
when the excitability of the nerve is lessened, the direct current causes contractions 
only at the very moment in which it begins to circulate, whilst the inverse current 
produces contraction only at the moment of its ceasing to pass. In one word, we 
can only judge of these phenomena by their presence or by their cessation. But in 
what relation these effects vary, in what order, as regards intensity, the phenomena 
of the first period of excitability of the nerve are transformed into those of the second 
period ; what relation the number of the contractions produced bears to the strength 
of the current, to its duration, & c., are so many questions which we shall never be 
able to solve without an apparatus by which to measure the contractions caused by 
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