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XIII. Electro-Physiological Researches. — Third Memoir. On Induced Contractions. 



By Signor Carlo Matteucci, Professor in the University of Pisa, 8fc. 8fc. 



Communicated by W. Bowman, Esq., F.R.S. 



Received July 23,— Read November 20, 1845. 



iHE term Induced contractions was applied in England to a physiological fact 

 discovered by myself, and described in the tenth chapter of my treatise on the Elec- 

 tro-physiological Phenomena of Animals. I shall henceforth adopt this denomination, 

 since it has the advantage of expressing the phenomenon with brevity, and, to a certain 

 degree, its nature. 



I will begin by explaining, in a few words, in what this fact consists, together with 

 the principal researches which I made in the commencement for the purpose of dis- 

 covering its laws. Having prepared a galvanoscopic frog, I laid its nerve upon one 

 or both the thighs of a frog prepared in the ordinary manner ; this done, on applying 

 the poles of a pile upon the lumbar plexuses of the frog, at the same time that the 

 muscles of the thighs were contracted, contractions were excited in the galvanoscopic 

 leg, the nerve of which reposed upon the thigh of the other frog. I discovered the 

 same fact, placing the nerve of the galvanoscopic frog upon a muscle of the thigh of 

 a rabbit, and exciting the muscle to contraction by means of a current which 

 traverses its nerve. I have even seen contractions of the galvanoscopic frog occur 

 without applying the electric current for the purpose of contracting the muscle which 

 ought to induce the contractions, adopting for this purpose any other stimulus to the 

 lumbar plexuses or to the spinal marrow. I finally tried these experiments, introducing 

 between the nerve of the galvanoscopic frog and the inducing muscular surface very 

 fine laminae of different substances. A leaf of gold and a very fine non-conducting 

 stratum of mica or of glazed paper being interposed prevented the phenomenon, that 

 is to say, the induced contractions in the galvanoscopic frog failed to appear, whilst 

 a stratum of fine paper soaked in water did not interrupt the induced contraction. 

 From the whole of these facts I was led to conclude, — 1st, that the contraction in- 

 duced in the galvanoscopic frog could not be attributed to the effect of derived cur- 

 rents ; 2nd, that it should rather be considered the effect of an electric discharge 

 taking place during the contraction of a muscle. For the sake of supporting this 

 explanation of the induced contractions by facts, I instituted a great number of ex- 

 periments which are described in the tenth chapter above referred to. With this 

 view I composed a pile of entire frogs, and closed the circuit with the two extremities 

 of the galvanometer. Allowing the needle to become stationary, I touched specially 

 the nerves of the frogs composing the pile with a solution of potassa, by which means 



