“As soon as a sensation, a sensational complex, a feeling, or a psychic process in general, arises in the mind during sleep from an outer or inner nerve-stimulus, and is perceived by the mind, this process calls up sensory images, that is to say, earlier perceptions, either unembellished or with the psychic values belonging to them, from the range of waking experiences, of which the mind has remained in possession. It seems to collect about itself, as it were, a greater or less number of such images, from which the impression which originates from the nerve-stimulus receives its psychic value. It is usually said here, as the idiom does of waking thought, that the mind _interprets_ impressions of nerve-stimuli in sleep. The result of this interpretation is the so-called nerve-stimulus dream—that is to say, a dream whose composition is conditioned by the fact that a nerve-stimulus brings about its effect in psychic life according to the laws of reproduction.” The opinion of Wundt[76] agrees in all essentials with this theory. He says that the ideas in the dream are probably the result, for the most part, of sensory stimuli, especially of those of general sensation, and are therefore mostly phantastic illusions—probably memory presentations which are only partly pure, and which have been raised to hallucinations. Strümpell has found an excellent simile (p. 84). It is as “if the ten fingers of a person ignorant of music should stray over the keyboard of an instrument”—to illustrate the relation between dream content and dream stimuli, which follows from this theory. The implication is that the dream does not appear as a psychic phenomenon, originating from psychic motives, but as the result of a physiological stimulus, which is expressed in psychic symptomology, because the apparatus which is affected by the stimulus is not capable of any other expression. Upon a similar assumption is based, for example, the explanation of compulsive ideas which Meynert tried to give by means of the famous simile of the dial on which individual figures are prominent because they are in more marked relief.