316 PROFESSOR MATTEUCCrS ELECTRO-PHYSIOLOGICAL RESEARCHES. 



We might believe it to be owing to an evolution of electricity independent of the 

 muscular and proper current; but how can we suppose it so, when we see that the 

 induced contraction propagates itself through certain insulating strata, as turpentine, 

 oil, &c., while it does not take place if we use an extremely thin plate of mica ? It might 

 be supposed that the electricity developed in the muscular contraction could have acted 

 by induction. In this hypothesis it is clear why the turpentine does not stop the in- 

 duced contraction, but it still remains doubly obscure why with the extremely thin 

 plate of mica this should take place. I have made an experiment by covering a 

 galvanoscopic frog, placed upon a plate of glass, with a sheet of mica ; the electric 

 discharge of a jar passes between the knobs of the universal discharger upon the sheet 

 of mica, and the contractions in the galvanoscopic frog are aroused. I shall not 

 occupy myself at this moment in analysing these facts ; it is sufficient at present to 

 prove that there must be induced contractions through the plate of mica if the occa- 

 sion of the phenomenon were an electric discharge. I will add finally, that I have 

 very many times attempted, and always uselessly, to awaken the contractions in the 

 frog, by holding the nerve of the galvanoscopic frog near and almost in contact with 

 a nietallic conductor traversed by the electric current. 



To place myself in favourable circumstances that the induced current may be com- 

 plete in the frog, I prepare it in such a manner that a long nervous filament (that is, 

 one of the lumbar plexuses with its continuation in the thigh) may be uncovered. The 

 frog is otherwise intact, and the two legs touch each other. I support the frog with 

 silken threads, so that it may be horizontal, and that its nervous filament may be in 

 contact and parallel with the voltaic conductor which is varnished. When every 

 care is taken to insulate the frog, signs of contractions are never seen in it either at 

 the closing or the opening of the circle of the pile. It is seen that by this disposition 

 the induced circuit may take place in the frog. I have used a Bunsen's pile of ten 

 elements without any result. 



There is therefore given no experimental proof of that explanation of the pheno- 

 menon of induced contraction which admits an evolution of electricity in the act of 

 muscular contraction. 



We are still ignorant of the cause of muscular contraction, and we know nothing 

 of this phenomenon except that it occurs on acting even at a great distance from the 

 muscle upon the nerve that ramifies within it; that this action requires for its propa- 

 gation the integrity of the nervous filament from the point at which it is acted upon to 

 the muscle; that this propagation acts with a velocity which we cannot judge to be 

 less than that of light and heat and electricity in their different media ; that that 

 which modifies, augments, or destroys the complication of the physico-chemical 

 phenomena comprehended in the nutrition of the muscles, operates equally upon its 

 contractility under any stimulus affecting the nerves ; finally, that the phenomenon 

 of the contraction of a muscle ought to be understood, with the condition that what- 

 ever be the cause of this phenomenon, it acts in accordance with the physical law of 



