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

whole extent of ramification of that nerve through the muscles; but that the contractions grow stronger in proportion as the irri- tation is applied near the central end. If, now, says Dr. Rernak, we keep an eye on this result, and then test the relation a nerve bears (while the central end is coursed through by a steady down-running current from a mod- erate battery,) to electric current fluctuations, we shall find, as Dr. Eckhard has already observed, the ability of the nerve to respond by the visible contractions of the depending muscles to the fluctuations of the current, and that to increase below and about the negative electrode, while this increase is found diminished again farther on towards the periphery. And sec- ond, we find that a constant steady current, which runs down the nerve in the neighborhood of the muscle, to operate quite differently; for it exerts its influence also upward, and occasions a decrease of the contraction or twitching produced in the neighborhood of the positive electrode by the fluctuations of a down-running current; but said decrease becomes less towards the top, and ceases altogether before the end is reached. Third, if the central end of a nerve is coursed through by an upward current, we shall find, it is true, that the susceptibility of the nerve and muscle to fluctuations of the current decreases below the positive electrode ; but it is also true, that this diminishes, and even ceases, before reaching the extreme part of the muscle. Fourth, and finally, if the steady up-running current operates in the neighborhood of a muscle, while at the same time a fluc- tuating current of another battery is all the while working above it, and in a different current direction, we shall find, to be sure, that the twitchings, or muscle contractions, increase in the vicinity of the negative electrode ; but it is also true, that this increase decreases again, in proportion as we approach the central end. Dr. J. Rosenthall has recently published a work on " The Modification of the Excitability of the Nerves by Means of con- stant Galvanic Currents and the Alternations of Ritter." The argument of this work may be comprehended in the following: Every constant current which courses through a nerve for a certain time, places the nerve in a condition in which the sus-