It has been said that during our waking hours the mind is kept incessantly active by the demands made on it through the senses. Naturally, therefore, sleep is most readily oh Mined when the avenues of sense are closed, so that the mind is cut of from the distractions that throng upon it. Thus the closing of the eyes, and darkness, cut off distractions conveyed by the organs of sight, and with silence the ear is powerless to stimulate. It is recorded of a boy who had only one eye and one ear that were of any use, and who, owing to disease, was other wise insensible to impressions from without, that the closing of his eye and the blocking up of his ear speedily put him to sleep.
The condition of the brain during sleep is one of considerable bloodlessness. There seems to be both a diminished quantity of blood cir culation through the brain, and the speed of its movement is lessened; whether this is the cause of sleep, or is the result of diminished activity of the organ—less demand and conse quently less supply,—it is difficult to say. Pro bably it is rather an effect than a cause of sleep. In sleep, then, the wind is cut off from the outside world. The question has arisen whether this is all, or whether sleep implies not only the interruption to the conveyance of stimuli to the mind by the avenues of sense, but also interruption to the activity of the mind itself. In a word, does the mind sleep too, or does it wake? On the answer to this question depends the explanation given of many very compli cated and interesting facts, such as those of dreaming and somnambulism. Many maintain that the mind is quite inactive during sleep, when the sleep is good. If the mind is quite inactive during ordinary profound sleep, there can, of course, be no dreaming, since that im plies an activity of the mind. So those who believe profound sleep to mean complete mental inaction, believe dreaming to be the mark of imperfect sleep, and to occur, therefore, when sleep is light, and specially in the stage be tween sleeping and waking. The main feature of dreaming is that however active the mind may be the will is in abeyance, and ideas and imaginations throng through the mind without let or hindrance in uncontrolled disorder. They are ideas with which the mind has been pre viously occupied, and which come up perhaps accompanied with their old associates, perhaps with other old ideas, not, however, formerly associated with them. They are frequently suggested by external circumstances, a sound setting up a rapid train of ideas which rushes across the mind in the interval before the per ' son is awakened by it. Or the suggestion may come from within—the pains of indigestion setting up dreams of terror, coldness of some part of the body suggesting to the sleeper that he has fallen into the water, and so on. Never theless it has happened that intellectual pro cesses of a high order have been carried on in dreams. Opposed to the view that the state of mind during sleep is one of inaction, is that view which holds that the mind is always active, :end that in sleep we are always dreaming, but that we do not remember our dreams unless we awake in the middle of them. It is time memory that is defective and fails to recall our dreams. This view offers a simple explanation of dreaming and of somnambulism.
Somnambulism is d ist n gu ish ed from dream ing by the fact that, while a person may recall his dreams, the somnambulist has no recollec tion of anything said or done during sleep. Somnambulism may be in the very simple form of talking in the sleep, or may amount to get ting up, walking about (this is what the word implies—sleep-walking), and engaging in vari ous kinds of activity. Cases are recorded of amen rising in sleep, dressing, and going out to their workshops or offices, of mathematicians working out obscure problems which had baffled them when awake, of lawyers writing out just and accurate opinions on difficult and intrieate points of law, concerning which they had been unable when awake to form a decision, of poets writing some of their most delightful verses, of musicians composing their most successful pieces, and of persons discovering articles that had been laid aside and the place forgotten. The credibility of such feats is denied by some emi nent men, and yet instances are given of such things being done. More than that, there are credible records of as marvellous feats being performed by persons who developed their power during attacks of madness, and of people displaying, during attacks of delirium due to fever, powers formerly unknown to themselves, and powers they no longer possessed when the delirium had passed. Thus Dr. Rush, an American physician, has recorded of a female patient of his who became insane after child birth, in the year 1807, that she "sang hymns and songs of her own composition during the latter stage of her illness with a tone of voice so soft and pleasant that I hung upon it with delight every time I visited her. She bad
never discovered a talent for poetry or music in any previous part of her life. Two instances of a talent for drawing," he adds, "evolved by madness, have occurred within my knowledge." Coleridge in his Biographia Literaria (p. 54, ed. 1870) relates the following case, which "occurred in a Catholic town in Germany a year or two before my arrival in Gottingen, and had not ceased then to be a frequent sub ject of conversation. A young woman of four or five and twenty, who could neither read nor write, was seized with a nervous fever, during which, according to the asseverations of all the priests and monks of the neighbourhood, she became possessed, and, as it appeared, by a very learned devil. She continued incessantly talking Latin, Greek, and Hebrew in very pom pous tones, and with most distinct enunciation. . . . The case had attracted the particular at tention of a young physician, and by his state ment many eminent physiologists and psycho logists visited the town and cross-examined the case on the spot. Sheets full of her ravings were taken down from her own mouth, and were found to consist of sentences, coherent and intelligible each for itself, but with little or no connection with each other. Of the He brew a small portion only could be traced to the Bible; the remainder seemed to be in the Rabbinical dialect. All trick or conspiracy was out of the question. Not only had the young woman ever been a harmless, simple creature, but she was evidently labouring under a nervous fever. Ln the town, in which she had been resident for many years as a servant in different families, no solution presented itself. The young physician, however, determined to trace her past life step by step; for the patient herself was incapable of returning a rational answer. He at length succeeded in discovering the place where her parents had lived ; travelled thither, found them dead, but an uncle surviv ing, and from Into learned that the patient had been charitably taken by an old Protestant pastor at nine years old, and had remained with him sonic years, even till the old man's death. Of this pastor the uncle knew flailing but that he was a very good man. With great difficulty, and after much search, our young medical philosopher discovered a niece of the pastor's, who had lived with him as his house keeper, and had inherited his effects. She re membered the girl ; related that her venerable uncle bad been too indulgent, and could not bear to hear the girl scolded; that she was willing to have kept her, but that after her patron's death the girl herself refused to stay. Anxious inquiries were then, of course, made concerning the pastor's habits ; and the solution of the phenomenon was soon obtained. For it appeared that it had been the old man's custom for years to walk up and down a passage of his house, into which the kitchen door opened, and to read to himself with a loud voice out of his favourite books. A considerable number of these were still in the niece's possession. She added that he was a very learned man, and a great Hebraist. Among the books were found a collection of Rabbinical writings, together with several of the Greek and Latin fathers; and the physician succeeded in identifying so many passages with those taken down at the young woman's bedside, that no doubt could remain in any rational mind concerning the true origin of the impressions made on her nervous systcm." Dr. Abercrombie relates cases where attacks of somnambulism came on, not during night, but during daytime. During the attack, which lasted some time, then passed off, and at some later period returned--- during the attack the persons were abstracted, and could do what was impossible to them after the attack passed off. One patient was an educated young lady who, on recovering from her first attack, found she had lost all her former knowledge, and set to work to regain it. She was making progress when she was seized with a second, which left her with her former state of knowledge quite restored. This alternation went on for four years, one attack leaving her without her former knowledge, and the next restoring it. In this case there was shown what is called double consciousness, is, things or persons that may have been seen, or things that may have been heard, during an attack were not remem bered when the attack passed off, but were re called during a succeeding attack. In the same way, anything seen or learned in the interval between two attacks was entirely forgotten in succeeding attacks, but was easily remembered in the intervals.