Insomnia; and Other Disorders of Sleep

by Henry M. Lyman

I. Insomnia caused by irritation of the peripheral portions of the sensory apparatus.

Irritation of the sensory apparatus may be ranked in three classes:

1. Affections of the organs of special sense.

2. Affections of the nerves of common sensation.

3. Affections of the sympathetic nerves.

1. Affections of the organs of special sense.—Prominent among these is the effect of light upon the eye. The darkness of night favors sleep; the presence of light hinders its incidence and renders it less profound. During the gloom of a total eclipse animals seek their shelter; birds hide themselves in their nests; domestic fowls arrange themselves upon the roost, and seem quite disconcerted by the speedy return of sunlight. Children often find it difficult to sleep in an illuminated room. I have known nurses who would sit with a wakeful infant under a powerful gaslight till after midnight, and then would express their surprise that the baby persisted in gazing at the flame instead of going quietly to sleep. The inhabitants of Northern Europe find it necessary to darken their sleeping rooms during the long polar day; and travelers in such regions often suffer for want of the natural sleep which only darkness affords. Judge Caton, writing of his travels in Norway[28] says: “We longed for darkness and for night. Do what we could to darken the windows to keep out the light, still it was not night as nature makes it, and which the habit of a lifetime had rendered necessary to sound repose. Artificial darkness, especially when incomplete, is as far from night as artificial light is from day.... These sunny nights can hardly conduce to health, they steal away so much of sleep. One does not readily get sleepy in the sunshine, and then we are so apt to forget to look at the watch to see if it is time to retire.”

In the tropical regions of the world it is usual for the inhabitants to sleep during the middle of the day; but they take great pains to exclude the light from their houses during the hours of sleep. The Pacific Islanders cover their faces with the bed clothes for the purpose of excluding the light while attempting to sleep. Repose thus obtained in the daytime often serves to convert the night into a season of wakefulness. The Africans sleep and dream away the heated hours of the day, and give up considerable portions of the night to festivity in the open air—a practice which undoubtedly contributes to the permanence of an inferior grade of social life.

Sudden illumination of the sleeping room will frequently awaken the sleeper. During the great fire in Chicago, A. D. 1871, many persons were thus aroused from their slumbers as the flames lighted up the streets adjoining their houses. One of my acquaintances was awakened one night by a flash of light from the lantern of a burglar who was moving noiselessly about her chamber. The experience of almost every one will testify to the effects of sheet-lightning silently illuminating the sky by night. Dreams, also, are not unfrequently excited by the incidence of light upon the closed eyelids.[29]

The sense of hearing is one of the most persistent of the special senses during the incidence of sleep. It is perhaps the most excitable of these senses during the period of repose. Long after the subject has become immersed in sleep his auditory apparatus remains sensitive to sounds. Dreams are often produced by impressions upon the ear. Often in sleep it seems as if the sense of hearing remained wakeful and watchful for expected signals, as when an alarm clock serves to arouse the sleeper at an appointed hour. Sometimes the sleeper may be shaken and tumbled about in his bed without waking, but if he be addressed by name he will usually reply. It is scarcely probable that the auditory apparatus is any more wakeful than other portions of the nervous system, but its external portions remain during sleep more completely exposed and adapted to the reception of impressions than is possible for the eye and for the organs of touch and taste.

The persistent sensitiveness of the ear during sleep is not so much a capacity for noticing sounds as a sensibility to variations in sonorous impressions. Thus a steady and monotonous noise may, if long continued, serve to render one sleepy; but the sudden cessation of the same sound will awaken every one. Slowly lulled to sleep by the incessant rumble of the engine upon one of the old-fashioned Long Island Sound steamboats, how immediate the awakening of a whole cabin full of people, when the wheels were suddenly stopped! A recent traveler in Guiana[30] relates a curious experience with an Indian magician who undertook to cure him of a slight headache and fever. The method of cure consisted in placing the patient at night in his hammock, while the magician kept up a hideous succession of yells and shouts, shaking the walls and roof of the house with an uproar which never ceased for six hours. Before long the patient passed into a kind of fitful sleep or stupor, during which he seemed to be suspended in a surging ocean of sound. When the noise died away, as if growing fainter in the distance, he would rouse up into a semi-conscious state, but when it again increased he would fall back into stupor. At last, when the noise finally ceased, he awoke completely, but without the slightest relief from headache—an experience quite illustrative of the manner in which the brain may be affected by sound.