we have just defined are found in observations, now old, made by Azam, Dufay, and other physicians. These observations are to-day well known and trite. They have been published and analyzed in a number of medical journals, and even in some literary ones.
The state of somnambulism is artificially induced in hypnotism, which may be brought about in a large variety of ways, in all of which there are reasons for supposing the psychological causes play the larger part. When one now comes to define somnambulism from the psychological point of view he sees at once that it constitutes a new mode of mental existence. The old mesmerists were quite right when they described it as a second personality.
Two fundamental elements constitute personality—memory and character. In the latter respect, as to character, induced somnambulism is not perhaps always clearly distinguishable from the waking state. It frequently happens that the somnambulist does not relinquish the character that he had before he was put to sleep. The reasons are manifold. This does not, however, hold for the second element of personality—memory. It has long been said that memory supplies the chief sign by which the new state may be distinguished from the normal state. The somnambulist shows, in fact, a curious modification in the range of his memory; the same regular phenomena of amnesia may be produced in him as occur in the spontaneous variations of personality.
Two propositions sum up the principal modifications of memory which accompany induced hypnotic somnambulism; first, the subject recalls during his waking state none of the events which happened during somnambulism; and second, on the other hand, when put in the somnambulistic state he may remember not only the previous somnambulistic states, but also events belonging to his waking state. It follows that memory attains its maximum extent in somnambulism, since it then embraces two psychological existences at once, as the normal memory never does. It may even be remarked that the somnambulist, when he endeavors to recollect certain particulars, has better memory than the same person awake. Gurney has shown, moreover, from studies of hysterical patients, that somnambulistic states may persist in the waking life; that the somnambulistic ego, the second condition, is not always completely effaced when the waking state returns, but survives, coexists with normal thought, and gives rise to complex phenomena of division of consciousness.
A second form of the phenomenon of double personality is the coexistence of the two egos, which is presented in two cases. The
