It may be, also, that other mental states more frequently met with and more easily observed present points in common with these more striking and unusual ones; and that they also may assist us in finding the clue.
NATURAL SOMNAMBULISM--HYPNOTIC SOMNAMBULISM--DREAMS.
The first of these more accessible conditions to claim attention is natural somnambulism, or sleep-walking. The phenomena of this peculiar state have been observed from time immemorial, and have always been looked upon as one of the most wonderful and interesting subjects in the domain of the old psychology.
In this state the subject, while apparently in ordinary sleep, arises from his bed and proceeds, sometimes to perform the most ordinary, everyday actions--cooking a dinner, washing clothes, sawing wood, or going out to a neighboring market town to transact business; sometimes, on the other hand, he does the most unusual things; he performs perilous journeys in dangerous and unfamiliar places in perfect safety and with unusual ease; sometimes intellectual work of a difficult nature, such as had baffled the student in his waking hours, is easily accomplished, and he finds the solution of his mathematical problem or the needed point in his argument all plainly wrought out and prepared for him when he goes to his desk the following morning; moreover, if the work from any cause should be interrupted, and the same conditions recur upon the following or some subsequent night, it may be resumed at the point where it was interrupted; or if the somnambulist talks, as well as acts, in his sleep the conversation shows that each succeeding occasion is connected with previous ones, all together constituting a chain of memories similar to that of the different personalities which have been presented in the four cases already described.
Sometimes all these different actions are accomplished without light or with the eyes fast closed, or else open and staring, but without vision. Sometimes, however, the new personality developed in the sleep of the somnambulist fails to come into proper relations with his surroundings, when he may also fail to accomplish the dangerous journey, and may walk from an open window or an unguarded balcony with disastrous results.