the reason why this dynamic state remains inactive until the signal sets it in operation. In some few cases, when a sensory signal is to call a posthypnotic hallucination into the upper consciousness, we can conceive of the sensory stimulus as the spark necessary to explode the stored-up energy of the cells and raise the idea to sensory level—make a thought seem vivid, intense, and external like a perception. But this conception is of limited application. The signal need not be sensory at all. It may even be a process of the higher orders, such as a perception of resemblance or difference, or even may consist in the lapse of time. I gave T some numbers to multiply and told him that if the figures 1 and 4 happened to stand side by side in the course of his work he would tear the whole up. When the numbers appeared in that relation he at once noted it and carefully tore the paper to tiny fragments. It is not easy to conceive of the suggestion as held in check by the mere lack of such a complex process of reasoning as this. Such difficulties I can not, I confess, explain away, and as long as they remain unexplained, the theory with which they are connected can not be accepted as final. It is to avoid them that some writers have introduced the conception of a subconscious personality which hears, remembers, and obeys without reference to the condition of the upper consciousness, and this brings me to the second question.
We usually conceive of our potential memories as existing in the form of a functional predisposition on the part of the nervous mechanism, and as having no actual mental existence while we are not thinking of them. At the first glance one would suppose that the posthypnotic suggestion exists in the same form. But cases have been reported which seem to prove that sometimes at least the posthypnotic suggestion enjoys an actual existence, even while the upper consciousness knows nothing of it. Thus Mr. Gurney says of Pll, one of his patients: "He was told on March 26th that on the one hundred and twenty-third day from then he was to put a blank sheet of paper in an envelope and send it to a friend of mine whose name and residence he knew but whom he had never seen. The subject was not referred to again until April 18th, when he was hypnotized and asked whether he remembered anything in connection with this gentleman. He at once repeated the order and said: 'This is the twenty-third day; a hundred more.' S. 'How do you know? Have you noted each day?' Pll. 'No, it seems natural.' S. 'Have you thought of it often?' Pll. 'It generally strikes me in the morning early. Something seems to say to me, You've got to count.' S. 'Does that happen every day?' Pll. 'No, not every day, perhaps more like every other day. It goes from my mind; I never think of it during the day. I only know it's got to be done.'"
