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

plaster, and exposed these raw patches to the immediate action of a pair of silver and zinc plates, he speaks of the effects in this manner: " As torpid or long-dead frog-thighs, at the com- mencement of galvanizing, twitch hardly any, if at all, but, after being brought for the third or fourth time in contact with the electrodes of a closed chain, the twitchings become lively, just so have I observed distinctly on myself that the first blows or shocks of a moderate current produced only a dull sensation, which, however, was perceptibly increased in degree, so that, from the fourth to the sixth contact of the connecting wires, they were of greatly augmented force. Does here the stimulus itself increase the excitability of the organs so that by the fourth to the sixth blow, while the irritation remains the same, the sus- ceptibility is become increased, or is the excitability not ex- alted, but, on the other hand, is the irritation aggregated in the muscle fibres ? Of these two suppositions, I am inclined to think the first as the most probable." Immediately after these declarations, M. Ritter, first of all,* by experiments observed that the closed chain does, indeed, alter the excitability of a nerve and muscle; for a steady current traversing a prepared leg and nerve of a frog, either through the nerve alone or through the nerve and muscles both, and for a long time, — say from half an hour to an hour, — will exer- cise an influence to change or decrease the irritability, so far as it shows itself by opening or closing convulsions. But the di- rection of the current employed produces very different results; and that,—namely, the down-running if a continuous current,— renders the thigh of the frog, in the course of an hour, incapa- ble of showing either closing or opening convulsions, if the same direction of the current is used ; but by then using the up-run- ning current, there will not only be produced, (after a half hour, or even whole hour,) at the opening of the chain, very strong twitchings, but it will even afterwards occasion tetanic contrac- tions, which can also be dissolved again by closing the chain. Thus two frog-thighs may be treated simultaneously in the same * Eewcis dass eiu selbeststandiger Galvanismus, etc., Weimar, 1798.