288 NERVOUS FORCE. LECT. XIV. XV. 



of the galvanoscopic frog in proximity with it, or even in 

 contact with a metallic conductor traversed by an electric 

 current. In order to find out the most favourable conditions, 

 and in order that the circuit by induction should be formed 

 and completed in the frog, I prepared the latter in such a 

 manner that a long nervous filament, that is, one of the 

 lumbar plexuses, and its prolongation in the thigh were 

 exposed. The remaining portion of the body was left 

 entire, and its two legs touched. I suspended the frog by 

 silken cords, in an horizontal position, and its nervous 

 filament being in contact and parallel with the voltaic 

 conductor, which was varnished. When all these precau- 

 tions are taken, in order that the frog may be perfectly in- 

 sulated, we never observe contraction excited in the latter, 

 at the commencement, at the opening, or at the closure of 

 the circuit of the pile. It must be remarked, that in this 

 experiment the circuit by induction may take place com- 

 pletely in the frog. I employed Bunsen's pile of ten ele- 

 ments, without obtaining any other result. .* ...^ . . 



From all this, it appears, that there is no experimental 

 evidence in favour of the explanation of the phenomenon 

 of induced contraction, by the assumption of the develop- 

 ment of electricity during muscular contraction. 



We are, then, still ignorant of the cause of muscular con- 

 traction, and all that we know of this phenomenon are the 

 following particulars: it is produced, even when acting at 

 great distances from the muscle, upon the nerve, whose 

 ramifications it receives ; the integrity of the nervous fila- 

 ment from the point where the excitation takes place to the 

 muscle itself is indispensable; this transmission is effected 

 with such rapidity, that we are compelled to compare it to 

 that of electricity, light, and radiant caloric, propagating 

 itself through various media ; what modifies, augments, or 

 destroys the accomplishment of the chemical physico-phe- 



