Sleep and Its Derangements

by William A. Hammond

“In a convent in Auvergne, an apothecary was sleeping with several persons; being attacked with nightmare, he charged his companions with throwing themselves on him and attempting to strangle him. They all denied the assertion, telling him that he had passed the night without sleeping, and in a state of high excitement. In order to convince him of this fact, they prevailed on him to sleep alone in a room carefully closed, having previously given him a good supper, and even made him partake of food of a flatulent nature. The paroxysm returned; but, on this occasion, he swore that it was the work of a demon, whose face and figure he perfectly described.”

That the imagination may in its flights during sleep strike upon fancies which are subsequently developed by the reason into lucid and valuable ideas, is very probable. It would be strange if from among the innumerable absurdities and extravagancies to which it attains something fit to be appropriated by the mind should not occasionally be evolved, and thus there are many instances mentioned of the starting-point of important mental operations having been taken during sleep. Some of these may be based upon fact, but the majority are probably of the class of those just specified, or occurred at an age of the world when a belief in the supernatural exercised a greater power over men’s minds than it does at the present day. Among the most striking of them are the following:

Galen declares that he owed a great part of his knowledge to the revelations made to him in dreams. Whether this was really the case or not we can in a measure determine by recalling the fact that he was a believer in the prophetic nature of dreams, and states that a man having dreamt that one of his legs was turned into stone, soon afterward became paralytic in this limb, although there was no evidence of approaching disease. Galen also conducted his practice by dreams, for an athlete, having dreamt that he saw red spots, and that the blood was flowing out of his body, was supposed by Galen to require blood-letting, which operation was accordingly performed.

It has been said[41] that the idea of the Divina Commedia occurred to Dante during sleep. There is nothing at all improbable in this supposition, though I have been unable to trace it to any definite source.

Cabanis[42] states that Condillac assured him that often during the course of his studies he had to leave them unfinished in order to sleep, and that on awaking he had more than once found the work upon which he was engaged brought to a conclusion in his brain.

These were clearly instances of “unconscious cerebration” of that power which the brain possesses to work out matters which have engaged its attention, without the consciousness of the individual being aroused to a knowledge of the labor being performed. It is not unlikely that this kind of mental activity goes on to some extent during sleep, but as it is of such a character that the mind does not take cognizance of its operations, I do not see how the exact period of its performance can be ascertained.

Jerome Cardan believed that he composed books while asleep, and his case is often adduced as an example of the height to which the imagination can attain during sleep. But this great man was superstitious to an extreme degree; he believed that he had a familiar spirit, from whom he received intelligence, warnings, and ideas, and asserted that when awake he frequently saw long processions of men, women, animals, trees, castles, instruments of various kinds and many figures, different from anything in this world. His evidence relative to his compositions and mathematical labors when asleep is not therefore of a trustworthy character.

As regards the memory in sleep, it is undoubtedly exercised to a considerable extent. In fact, whatever degree of activity the mind may then exhibit is based upon events the recollection of which has been retained. But there is more or less error mingled with a small amount of truth. The unbridled imagination of the sleeper so distorts the simplest circumstances as to render their recognition a matter of no small difficulty, and thus it scarcely if ever happens that events are reproduced during sleep exactly as they occurred or as they would be recalled by the mind of the individual when awake. Frequently, also, recent events which have made a strong impression on our minds are forgotten, as when we dream of seeing and conversing with persons not long dead.

And yet it has sometimes happened that incidents or knowledge which had long been overlooked or forgotten, or which could not be remembered by any effort during wakefulness have been strongly depicted during sleep. Thus Lord Monboddo[43] states that the Countess de Laval, a woman of perfect veracity and good sense, when ill, spoke during sleep in a language which none of her attendants understood, and which even she was disposed to regard as gibberish. A nurse detected the dialect of Brittany; her mistress had spent her childhood in that province, but had lost all recollection of the Breton tongue, and could not understand a word of what she said in her dreams. Her utterances applied, however, exclusively to the experience of childhood, and were infantile in structure.

Abercrombie[44] relates the case of a gentleman who was very fond of the Greek language, and who, in his youth, had made considerable progress in it. Subsequently being engaged in other pursuits, he so entirely forgot it that he could not even read the words; often, however, in his dreams he read Greek works, which he had been accustomed to use at college, and had a most vivid impression of fully understanding them.