ABSTRACT
In my book Mneme I distinguished between synchronous, acoluthic, and engraphic effects of stimulation. A “synchronous” effect is that which ceases immediately with the cessation of the stimulus; “synchronous original excitations” are those which that stimulus awakens; and “synchronous original sensations” are their manifestations in the sphere of sense. As regards acoluthic effects of stimulation I expressed myself as follows. 1 : “A very intense or prolonged effect of stimulation sometimes causes such profound changes in the state of an organism, that for it to settle down again to return to its original condition some considerable time after the stimulus has ceased is necessary just as the sea after a great storm only reverts by degrees to calm.” We are accustomed to describe this process as the dying down of an excitation (abklingen der Erregung). When several discontinuous excitations follow one on the other so quickly that the earlier are overtaken by the subsequent ones, the results of excitation come ever more and more to resemble a single prolonged constant excitation and arouse in us continuous sensations—(cf. the continuous colouring of a rapidly rotating variegated top, or the single tone of a quickly turning Savart’s wheel). To the same class (even when one cannot speak exactly of dying down) belong “after-images” and “after-tones”; also the convulsive jerks and con tinued contractions which follow on a prolonged stimulation of the muscles through electricity. Such after-effects, 136which always vanish without trace some time after the stimulus has ceased, are not distinguishable in principle from synchronous effects of stimulation, not even when the pendulum of reaction swings over-much to the other side as is, for instance, the case in the negative “afterimage.”
