^84 PROFESSOR MATTEUCCl'S ELECTRO-PHYSIOLOGICAL RESEARCHES. 



finally, the frog is divided into two parts by cutting the juncture of the two thigh- 

 bones. In this way there remain two halves of the frog united together organically 

 by their spinal nerves. When this frog is required to be used for the purpose of dis- 

 covering the presence and direction of the muscular current, it should be disposed 

 upon an insulating plane in such a manner that its two extremities or claws dip 

 into two separate recipients. Joining these two recipients with strings of cotton 

 or thread, soaked with the same liquid as that contained in the recipients them- 

 selves, or with a strip of paper similarly wetted, no sign of contraction is ever pro- 

 duced, therefore no current is in circulation. This last fact may easily be proved 

 by closing the circuit with the two ends of the platinum wire of a delicate galva- 

 nometer, provided we can be perfectly certain of the homogeneity of the sub- 

 stance of the extremities of the wires. And it will be seen that it cannot be other- 

 wise, on reflecting that each half of the frog constitutes an electro-motor element 

 of the proper current, so that, in the above-described manner of using the prepared 

 frog, there are always two equal currents circulating in contrary directions, and 

 which consequently neither excite contractions, nor deflect the needle of the galva- 

 nometer. 



There is nothing easier, and at the same time more decisive, than the confirmation 

 of the existence of the muscular current and of its direction. 



A pile consisting of thighs of frogs, or of muscles of other animals, should be pre- 

 pared in the manner I have described in my work that I have quoted above. The 

 two extremities of this pile (the internal surface of the muscle on the one hand, and 

 the external on the other) should dip in distilled or spring water. When the frog is 

 prepared as already described, and stretched upon the insulating plane, the extreme 

 cavities of the pile are made to communicate with the two recipients in which the 

 claws of the frog are immersed, by means of strings of thread or cotton soaked with 

 water (Plate III. fig. 1.). The frog is then distinctly seen to contract both on closing 

 and on breaking the circuit ; but both limbs do not contract equally, since that 

 which is traversed by the current, and which consequently is near that extremity of 

 the pile which is formed by the internal surface of the muscle, contracts on closing 

 the circuit with the direct current, while, on the contrary, the other limb, which is 

 near the extremity of the pile formed by the external surface of the muscle, contracts 

 on breaking the circuit. Simply by the aid of the frog so prepared, it is possible to 

 confirm the principal laws of the muscular current, which I have already discovered 

 with the galvanometer. Thus it happens that the contractions of the galvanoscopic 

 frog increase proportionally with the number of elements ; and they are the same 

 for a pile formed of muscular elements deprived of all visible nervous filaments, as 

 for a pile the muscular elements of which are intact. The same takes place operating 

 with a pile composed of muscular elements taken from frogs killed by the action of 

 narcotic poisons, carbonic acid, prussic acid, &c. Finally, with the galvanoscopic 

 frog it is easy to discover the immense difference which exists between the signs of 



