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

legs of a frog prepared after the original manner as clone by Galvani, and immerse the two legs respectively in two glass ves- sels which are nearly filled with water, and now plunge a pole of a weak current into each of these vessels, we notice that con- tractions do not take place in each at the same time, provided, always, that the legs have lost some of their excitability, so as to make the differences more distinctive. Now, a contraction will be observed, on making the circuit, in that leg in which the current is direct or down-running ; but it will be on breaking the circuit in the other leg in which the current is inverse or up-running. Then, if the irritability in the preparation be al- lowed to be still further diminished by time, or by treatment for experiments, only one kind of contraction will remain, namely, that first produced by making the direct current at each time; if the irritability be still further diminished, all contractions or twitchings of any sort whatever will disappear. If a gentle, continuous current be applied to a nerve, the nerve will retain its excitability very long, — i. e., to the touch of a reversed current, — and will not be injured as much as is done by applying moderate mechanical or chemical stimuli. But if the continuous current be of great quantity or high in- tensity, — if, instead of a single battery, there is employed a large size series, or if, instead of a single pair, there is employed a numerous pile, — then, just as we might expect, the nerve will be destroyed by the chemical action at and about the electrodes. Finally, as I have said, Nobili gave these differences of con- tractions, which so elicited the early attention of philosophers, a most elaborate series of investigations. He concluded, finally, that there were five different stages, kinds, or degrees of con- tractile response, in nerves and muscles, to the same given strength of electric current. But we now conclude that some of those differences that he found, arose from experimenting on dead frogs, not on living animals or men, and that the difference in results obtained in those early times, by equally honest exper- imenters, mostly arose from using widely different electric apparatus and currents, as to quantity, intensity, or the given density of the stream employed. 16