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

and then, still later, by Xobili, Marianini, and Matteucci; and then, again, more recently, by Dubois-Reymond, Faraday, Mar- shall Hall, Becquerel, Duchenne, Todd, Bird, Remak, and Al- thaus. The larger class of those early experiments was directed mainly to ascertain the law of current direction and the laiv of convulsion. It was very soon observed that the nerves of the batrachian tribe, — those famed martyrs to science, — were so sensitive to the electric stimulus that only the more gentle currents of the pile could be employed ; for if the current was strong, whether up-running or down-running, the commotion was so great that the real difference could not readily be observable. M. Pfaff early drew attention to the particular difference in the phenom- ena that presented on running a mild current vp or down a nerve ; for if the current of a powerful pile be used, no such differences would be uniformly observed. But by using the cur- rent of a single pair of steady and continuous action, we observe the following: Where the frog is vigorous and but recently killed, and the nerves of the prepared legs are consequently in the highest degree of excitability, we usually see contractions both at the closing and at the opening of the circuit, and that whether the current runs down or up. But if, after a longer time, or by repeated teasing with the galvanism, the legs and nerves have lost a part of their excitability, then a very marked difference is noticed in the physiological effects. Now, if we first direct a down-running current through the ischiatic nerve, the contraction, which is a mere momentary twitch, is observed only at the first moment the current is applied, but not while the current continues to traverse the nerve, nor yet at the mo- ment when it ceases to pass. But if an up-running current be applied to that nerve, with say a half-inch space between the poles on the nerve, just as in the former case, we observe there are no contractions at the first moment the current is applied, nor yet while it continues to traverse the nerve, but only at the moment when the circuit is broken, and the current ceases to pass. Again: if we employ in these researches the united pair of