. Electro-physiology. Electrophysiology. ix ELECTRICAL EXCITATION OF XERVF, 189. corresponds with the existing tonus), and then, sooner or later, makes a sudden drop below it (Fig. 196), either rising again immediately, or more slowly, after a certain interval, so that the lever often recovers its initial position during closure, in other cases, however, only when the circuit is opened. It not infrequently happens, at a given strength of current, that the shortening of the tonic muscle, 011 closing the circuit, corresponds both in magnitude and dura- tion with the subsequent relaxation, so tha
. Electro-physiology. Electrophysiology. ix ELECTRICAL EXCITATION OF XERVF, 189. corresponds with the existing tonus), and then, sooner or later, makes a sudden drop below it (Fig. 196), either rising again immediately, or more slowly, after a certain interval, so that the lever often recovers its initial position during closure, in other cases, however, only when the circuit is opened. It not infrequently happens, at a given strength of current, that the shortening of the tonic muscle, 011 closing the circuit, corresponds both in magnitude and dura- tion with the subsequent relaxation, so that the first section of the curve above the abscissa is almost equal with that of the lower half (Fig. 196). In current- intensities below this limit, the second half of the curve seems generally to preponderate, while beyond it the effects of excitation come more and more into play at the expense of the inhibiting action—so that the first section of the curve is highly characteristic. The inhibitory effects are often so indefinite, that their existence as independent signs of stimulation might easily be overlooked, without some knowledge of the action of weaker currents; and they might be viewed merely as fatigue- effects from the immediately preceding persistent excitation. This is indeed contradicted by the fact (as insisted on above) that re-entry of the more or less strongly inhibited tonus usually occurs during the passage of the current; while, moreover, the break of a stronger current not unusually inhibits to the same extent as the closure of a weak current. On opening the exciting circuit a fall of the curve similar to that previously obtained during closure (Fig. 195,c) is apparent. We thus learn that the reaction of the tonically contracted adductor muscle, on exciting its nerve with the constant current, is characterised throughout (with increasing strength of current) by depression of inhibitory effects in favour of excitatory action, until the inhibition becomes
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