No repetition of the memory of the unpleasant experiences with their associated emotion of misery and fear led to the formation of a habit of mind and feeling. And when once such a habit of mind is established it is remarkable by what a host of stimuli received in ordinary daily life the cause of the disturbance can be recalled. This question of stimuli deserves further notice. It is not so difficult to realize the mechanism by which a stimulus which clearly crosses the threshold of consciousness can lead to a given reaction. But it is perhaps difficult to imagine how so many stimuli which do not cross the threshold of consciousness or which, if they do, are not recognized by the patient at the time as having any reference whatever to the special memory can yet set the memory mechanism into action. The result may not be seen till after the relapse of some considerable period of time, as in the case of a man who for years had been disturbed by terrific nightmares, based on the idea of snakes coming out of the ground and attacking him. He complained one day that he was much worse, that three nights before he had had the worst nightmare of his life. On being questioned as to what could have suggested snakes to him he could not tell. A few minutes later he said: "I think I know the cause now. I spent the evening before I had that nightmare with a sergeant who had returned from the service in India." This friend amongst other things had mentioned that whenever they were about to bivouac they had to search every hole under a stone and every tuft of grass to see that there were no snakes there. This, which had been received as an ordinary item of information, had been the stimulus which had set his memory mechanism into action and the nightmare between two and three o'clock in the morning had been the result.