Sleep and Its Derangements

by William A. Hammond

A gentleman of a nervous and irritable disposition informed me that he had dreamed of being in heaven and being dazzled by the brilliancy of everything around him. So great was the light that he hastened to escape from the pain which it caused in his eyes. In the efforts which he made he struck his head against the bedpost, and awoke to find that the fire which he had left smouldering on the hearth had kindled into a bright flame, the light from which fell full in his face.

Another, who had been under my care for epilepsy, dreamed that his room was entered by burglars, and that with lighted candles in their hands they were searching his drawers and trunks. He related his dream the following morning, and was told by his mother that she had gone into his room the previous night, and had held a lighted candle close to his face in order to see whether or not he was sound asleep.

No one has more philosophically studied the mode of production of dreams than M. Maury[83] in his remarkable work to which reference has already been made. I propose, therefore, to place a brief outline of his experiments and views before the reader.

Just before falling asleep, and immediately before becoming fully awake, many persons are subject to hallucinations partaking of many of the characteristics belonging to dreams. To them the name of hypnagogic (ῦπνος, sleep, and ἀγωγεύς, leader) hallucinations has been given, i.e. hallucinations which lead to sleep. Previous to M. Maury’s investigations, the phenomena in question had attracted some attention from German and French physiologists, but M. Maury’s investigations, many of which were performed upon himself, throw more light upon the subject than it has hitherto received.

According to M. Maury, the persons who most frequently experience these hypnagogic hallucinations are those who are of an excitable constitution, and are generally predisposed to hypertrophy of the heart, pericarditis, and cerebral affections. This may be true, but in two most remarkable instances which have come under my observation, the type of organization was the very reverse of this.

In M. Maury’s own case he finds that the hallucinations are more numerous and more vivid when he experiences, as is frequent with him, a disposition to cerebral congestion. Thus, when he has headache, nervous pains in the eyes, the ears, and the nose, and vertigo, the hallucinations make their appearance as soon as he closes his eyelids. Loss of sleep and severe intellectual exertions invariably produce them, as do also cafe noir and champagne, which, by causing headache and insomnia, strongly predispose him to the hypnagogic hallucinations. On the contrary, calmness of mind, rest, and country air lessen his liability to them. From the inquiries made of others by M. Maury, the results of his own experience, as well as from my own observations, I am well convinced that the hypnagogic hallucinations are directly the result of an increase in the amount of blood circulating through the brain rather than to actual congestion as he supposes. They therefore indicate the existence of a condition unfavorable to sound sleep. In the chapter devoted to the consideration of wakefulness the phenomena accompanying cerebral hyperæmia will be more fully considered.

The theory which M. Maury proposes in order to account for the existence of hypnagogic hallucinations further presupposes that as the power of the attention immediately before sleep begins to be diminished, and the mind cannot therefore voluntarily and logically arrange its thoughts, it abandons itself to the imagination, and that thus fancies arise and disappear unchecked by the other mental faculties. This absence of the attention need not be of long duration, a second, or even a shorter period being sufficient. Thus he lay down, and the attention which had been fully aroused soon became weakened; images appeared, and these partially reawakened the attention, and the current of his thoughts was resumed, to be replaced again by hallucinations, and this continued till he was fully asleep. As an example, he states that on the 30th of November, 1847, he was reading aloud the Voyage dans la Russie Méridionale, by M. Hommaire de Hell. He had just finished a line when he closed his eyes instinctively. In this short instant of sleep he saw hypnagogically, but with the rapidity of light, the figure of a man clothed in a brown robe, and with a hood on his head like a monk. The appearance of this image reminded him that he had shut his eyes and ceased reading. He immediately opened his eyelids and resumed his book. The interruption was practically nothing, for the person to whom he was reading did not perceive it.

M. Maury gives numerous examples of these hypnagogic hallucinations, all tending to show that they are induced by a congested condition of the cerebral vessels, and that thus, according to the views I have set forth relative to the condition of the brain in sleep, they are not to be regarded as precursors of that state, but of stupor.

In two very interesting cases of these hallucinations, which have come under my notice, they were brought about by any cause which increased the quantity of blood in the brain, or retarded the flow of blood from this organ. Thus, a glass of champagne, or a few drops of laudanum, would induce them, as also would the recumbent posture, with the head rather low.

As showing how readily dreams can be excited by impressions made upon the senses, M. Maury caused a series of experiments to be performed upon himself when asleep, which afforded very satisfactory results, and which are interesting in connection with the points already discussed in the present chapter.