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PROFESSOR MATTEUCCI’S ELECTRO-PHYSIOLOGICAL RESEARCHES. 
A difference, however, does exist on interposing a lamella of gold or of mica be- 
tween the galvanoscopic nerve and the muscle: these lamellae prevent the induced 
contractions without destroying the effect of the discharge of the jar. I am far from 
concluding from the above fact that the two phenomena may not have the same 
origin. We have no precise knowledge as to why the discharge of the jar can be 
very slight without its ceasing to excite contraction in the galvanoscopic frog ; and 
we have seen in those cases in which the lamellae of mica or of gold were interposed, 
that the number of successive discharges from the jar, which acted upon the galva- 
noscopic frog, was always less than when no lamellae were interposed. 
We must therefore pause a little before we can establish the fact of induced con- 
tractions not being due to an electric discharge produced during the contraction of 
the muscle ; and since it is impossible for us to solve the question by direct experi- 
ment, let us be guided by such analogies as appear to have the best possible foundation. 
I purpose examining this field of investigation in a general summary of all my electro- 
physiological researches, which summary I hope soon to be able to complete. 
PART II. 
Upon the Phenomena elicited by the passage of the Current through the Nerves of a 
living Animal, or an Animal recently killed, according to the direction of the Current. 
In my fourth memoir I took great pains to prove at length by the aid of experi- 
ment, that the electric current transmitted along a nerve modifies the excitability of 
the nerve in a manner differing widely according to the direction of the current; 
thus the direct current rapidly exhausts this excitability, while the inverse current 
increases it. Starting from this fact, I hope that I have given a satisfactory theory 
of electro-physiological phenomena. 
Among the different experiments described on this head, I indicated one in parti- 
cular which appears very singular, and which I have since studied in all its bearings. 
The frog prepared in the ordinary manner, and divided in the pelvis, is placed astride 
between two little glasses in which the reophores of a Faraday’s pile of fifteen or 
twenty elements were immersed. It is evident that one of the limbs is traversed by 
a direct current and the other by an inverse current. It is unnecessary to describe 
here minutely the phases of the phenomena which present themselves during twenty 
or twenty-five minutes. 
In the first place, the two limbs contract both on closing and on opening the cir- 
cuit, after which there is contraction of the limb traversed by the direct current on 
closing the circuit ; and the other limb contracts on breaking the circuit : finally, 
only one limb contracts, viz. that ot the inverse limb on the cessation of the passage 
of the current. On keeping the circuit closed for some minutes, we invariably remark 
that the inverse limb, which contracts on breaking the circle, is seized with a perma- 
nent contraction of a decidedly tetanic character. This phenomenon is of importance, 
