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

But all these results, obtained so uniformly by experiments on dead or mutilated animals, we find to vary, considerably, when tried on living human beings. The phenomenon is greatly varied with the strength, and way, the current is brought to bear upon the individual; and besides there are wide differences in persons as to less or greater nerve excitability. Relatively speaking, then, we can say, that the more powerful currents show their effects most at the instant of opening the circuit, and that the reverse is true when employing a more feeble bat- tery current. This must be due to the greater degree of the modification brought about by the recent running current through the nerves. M. Nobili believes that his law of con- traction is not affected, if we include also the muscle with the nerve, i. e., if one electrode is over a nerve, while the other is upon the muscle that is supplied by it. But he thinks the effect is no longer the same, if the current is directed so as to traverse only the muscle fibres; for in that case, the twitch takes place only when the circuit is closed, and that regardless of the direc- tion of the current. But we do not observe now the contraction that was otherwise produced at the opening of the circuit, and hence called the opening convulsion. This last phenomenon, when produced, is no doubt the result of the modification pro- duced in the nerve trunk while it was being traversed by the previous somewhat strong current, as we have before shown. Dr. Yolta early made trials in the ordinary manner with the recently-killed frog. He placed the legs, when properly pre- pared, astride of two glasses of water, so that one foot should be in each of the glasses. He then brought the current of a moderate pile to pass steadily through these legs, up one and down the other, by placing the electrodes respectively in the two glasses of water. This he would maintain for a half hour, when the legs would no longer twitch, either while he made or broke the circuit. But on exchanging the poles, so that the current passed now in the opposite direction, then neither closing nor opening of the circuit could be done, without the contraction being repeated strongly at each time. If the exchange was then again made, and in like manner continued for a half hour, at