those elements which yielded the physical basis of the dream, and which, had they originally occurred during the waking state, might have persisted with energy sufficient to furnish a groundwork for recollection of the ideas which they had first suggested, are no longer sufficiently forcible to be felt in consciousness. Recollection of mental states thus generated must necessarily be impossible under such conditions. Sometimes, however, the somnambulist who, while awake, had forgotten all the incidents of his somnambulic experience, can remember, in a subsequent paroxysm, all that occurred during the preceding attack. Facts of this kind have been observed in the waking life of certain hysterical persons, but the apparent doubling of their personality is connected with the waking state, or with its semblance, while in ordinary somnambulism it is only during sleep that the alternations of memory and forgetfulness occur. A similar recollection of previous visions is sometimes experienced in dreams, showing a close relationship between the dreams of sleep and of somnambulism. The bond of association between events thus isolated in time must be sought in a renewal of like conditions of the brain during the successive periods of somnambulic exaltation. We must suppose that the molecules which were in a state of excitement during the first paroxysm are again aroused in a similar manner after a period of waking quiescence. If, during sleep, their movements, though of an exalted character, have only just sufficed to arouse consciousness in the form of a dream, it is scarcely probable that during the phase of comparative inactivity which supervenes when the whole brain is awake, their residual motion could disturb the sphere of consciousness. Hence the time occupied by their somnambulic vigor must remain a blank in memory during the waking state. But, when the original state of relative exaltation has been reproduced by a second paroxysm of disorder, if the same molecular movements be in any way renewed, the conditions of memory are fulfilled; consciousness is once more aroused as before, and the patient remembers the dream or the events of the previous attack. CHAPTER VII. ARTIFICIAL SOMNAMBULISM OR HYPNOTISM. There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy. --HAMLET.