Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

traversed with the direct or down-running current, is seen to tremble at the closure of the current, whilst at the opening of the same the trembling is seen in the other frog legs, where is the positive pole, and the current is traversing indirectly, or up- running. This trembling in the one experiment, and the twitch- ing in the other experiment, arise, as we see, under opposite directions of the current. Marianini further observed, that when electricity acts imme- diately over and upon a muscle, contraction takes place only at the instant when the current is closed, whatever be the direction of the stream. He therefore termed this mode of action the idiopathic, to distinguish it from the action produced by apply- ing the electrodes over the nerve trunk of that muscle which he termed symptomatic. By thus operating on a live frog, whose posterior limbs remained attached to the living animal only by the two carefully exposed nerves, (sometimes termed lumbar, sciatic, ischiatic, or crural nerves,) and placing the hind legs in contact with one pole of the battery, while one or both of the fore legs are in contact with the other pole, as by placing them respectively in little shallow vessels of water, — if now the stream traverses the hind legs directly, or down-running, the frog will agitate those posterior limbs at the moment when the current is closed. But then, at the moment when the current is opened, the frog utters a prolonged cry with the full force of its lungs, as from pain, and at the same time raises itself with rigid con- tortions on its fore legs or arms, without the least agitation of the posterior legs. Then, after a considerable rest, if the cur- rent is reversed so as to enter the hind legs by the feet, and hence in an inverse direction, it is now, when the current of electricity is closed, that the frog utters its cry, accompanied with contortions, &c, and it repeats the cry if the circuit is left a little longer closed; but when opened, the posterior extremi- ties are agitated again, and the animal ceases to cry or show contortions. By this we see that the contractions take place only at the closing or making of the circuit, and not at its opening, if the current or stream is direct, or down-running; and only appear- 18*