Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
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in a longitudinal direction; or, better still, if in a somewhat oblique and longitudinal course, so as to thus embrace the great- est possible number of nerve filaments, although the position of the electrodes on the skin may be close together. Muscular contractions in the living human organism cannot be produced from the excitation of pure motor nerves by an electric current, unless those nerves are in some little degree or sense possessed of their normal integrity. True it is, that the electric stimulus is capable of so disturbing the molecular equi- librium of the motor nerves and their depending muscles, as to produce the state in which they are physiologically active ; and this disturbance, if judiciously made, does not cause any injury to nerve, muscle, or central organ, but rather tends to reestablish the lost or impaired vital functions of the reciprocal actions of nerve, muscle, and central organ, whenever so lost, provided they are under the above conditions. Dr. Bernard has shown that if a motor nerve is galvanized, while in its normal physiological condition, — i. e., while it is still connected with the spinal cord of the living animal, then a contraction is produced only on closing- the circuit, be the direction of the current either direct or inverse. But if the nerve is some fatigued by energetic or very prolonged action, by heat, or by any other means, then two contractions are produced by either current, the one at the closing of the circuit, and the other at its opening. There- fore, if this phenomenon is observed in practice, we calculate that the nerve is fatigued; i. e., it is in a degree exhausted. Then, again, if the fatigue is greater still, the contractions are only observed on closing the direct, and opening the inverse, current. If the fatigue is still greater, we obtain only a single contraction, and that only on closing the direct current. Then, if the fatigue is even greater still, and the exhaustion is total, — i. e., complete and final, — there is no more contraction pro- duced under any circumstances whatever. This is strictly peculiar to the nerves of living human beings. Again, we have already shown, that during the time a con- tinuous, moderate, and even-flowing galvanic current is travers- ing a motor nerve, no visible contractions occur, although a real