If that explanation should meet with scepticism I would remind the reader that the wealth of information with which our unconscious is filled permits of unconscious mental operations of which in our conscious states we would be incapable. Janet's subject, Lucie, who was lacking in mathematical ability, could, in her unconscious states, perform calculations of an extreme complication. He would give her under hypnosis the following order: "When the figures which I am going to read off to you, leave six when subtracted one from the other, make a gesture of the hand." Then he would wake her up, and ask several people to talk to her and to make her talk. Standing at a certain distance from her, he would then read rapidly in a low voice a list of figures, but when the appropriate figures were read, Lucie never failed to make the gesture agreed upon. We notice thousands of things unconsciously, which means simply that every sensorial impression causes a modification of our autonomic system and probably of our sensory-motor system which is never completely effaced. During our waking hours only those memory impressions which are needed rise to consciousness. The many observations we have made, consciously or otherwise, enable us to calculate the distance between us and an automobile, the speed of that automobile, the width of the street, the dryness or the slippery conditions of the pavement, and to select the time for crossing as well as the speed at which we shall cross. In our sleep, when we are revolving the day's problems and searching for solutions, many other facts, stored up in our nervous systems, rise to consciousness and are used in solving the problem. In the personal case I cited, my unconscious applied its searchlight to recent events; in other cases reported in the literature of the subject the unconscious is shown bringing back events which seemed to have been entirely forgotten. Our organism never forgets. Forgotten incidents which suddenly rise to consciousness in dreams are sometimes responsible for visions which on superficial observation appear truly prophetic. Maury cites the following in his book on "Sleep and Dreams": "Mr. F. decided once to visit the house where he had been brought up in Montbrison and which he had not seen in twenty-five years. The night before he started on his trip, he dreamt that he was in Montbrison and that he met a man who told him he was a friend of his father. Several days later, while in Montbrison he actually met the man he had seen in his dream and who turned out to be some one he really knew in his childhood, but had forgotten in the intervening years. The real person was much older than the one in the dream, which is quite natural."