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

because the passage of the electric current along the spine excites the action proper of the spinal cord, which in its turn excites the property and office of the motor nerves to bring about commo- tion of the muscles. This species of reflex action is often as clearly illustrated in patients, who present for examination with uncertain lesions of the spine. Whenever tetanic convulsions are produced in the extremities, by thus immediately Faradaizing the cord, they continue a little after the electrodes are removed ; but if the anterior root, or even the whole mixed nerve trunk, is thus excited at some little distance from the spine, instead of applying it to the cord itself, the tetanic convulsions disappear the instant the circuit is opened. Another fact: it has lately been observed by Dr. Baielacher, that if induction currents are applied to the large motor nerves of the hinder extremities of an animal, while the spinal cord is at the same time being traversed by a constant galvanic current, then commotions are produced in tbose muscles, the nerves of which are being traversed by the interrupted current.* There- fore he infers, that the diminution of excitability from the action of a continuous current is limited in the spinal cord, and hence does not extend to the motor nerves and their depending muscles. Besides, if the whole spinal cord is caused to be traversed (i. e., lengthwise) by a strong, continuous galvanic current, it is ob- served that at the instant it commences to flow, there is a quick contraction in the muscles of all the limbs ; but after that, and as long as the current then continues to flow undisturbed, even if for a long time, no more contractions appear; and the ex- posed spinal cord itself even, remains insensible to any stimulus whatever that may be applied to it; as, for example, pricking, pinching, heat, or induction currents ; nevertheless all remains perfectly quiet. But, after the cessation of this current through the exposed cord of the mutilated animal, then again will the mere mechanical touch, or the reversed electrical excitation of the cord, give rise to twitchings of the muscles, and even con- tractions of the limbs, if the animal is still alive, and that in a * Die Inductions-Electricitat, Nurnberg, 1857, p. 102.