More practically, and from a totally different point of view, M. Chabaneix, having studied the continuous subconscious, divides it into nocturnal and waking subconsciousness. If the former be a question of sleep or of the moments preceding sleep, it is oneiric or pre-oneiric. Maury, who was particularly afflicted by them, has carefully considered the hallucinations which are formed the moment the eyes close in sleep. It is not clear that these hallucinations which are called hypnagogic, and which are almost always visual, can have a special influence on the ideas undergoing elaboration in the brain. They are rather embryonic dreams which influence the course of the thought only as dreams influence it. It happens, at times, that the conscious effort of the brain is prolonged during the dream, even reaching its goal there, and that, on awaking, the dreamer finds himself, without reflection or difficulty, master of a problem, a poem, a combination, which had baffled him previously. Burdach, a Koenigsberg professor, made, in his dreams, several physiological discoveries which he was afterwards able to verify. A dream was sometimes the point of departure for an undertaking. Sometimes a work was entirely conceived and executed during sleep. It is highly probable, however, that it is the conscious reason which, at the moment of awaking, judges and rectifies the dream spontaneously, gives it its true value, and divests it of that incoherence peculiar to all dreams, even the most rational.