And as when heavy sleep has closed the sight, The sickly fancy labours in the night: We seem to run; and, destitute of force Our sinking limbs forsake us in the course; In vain we heave for breath; in vain we cry; The nerves unbraced their usual strength deny; And on the tongue the falt'ring accents die.

- Vergil, Æneid, B. XII.

Of all the distressing, terrifying experiences which may be the lot of man, nightmare is probably the worst. As Macnish1 says: "This affection, the Ephialties of the Greeks, and the Incubus of the Romans, is one of the most distressing to which human nature is subject. Imagination cannot conceive the horrors it frequently gives rise to, or language describe them in accurate terms. They are a thousand times more frightful than the visions conjured up by necromancy, or diablere; and far transcend every thing in history or romance, from the fable of the writhing, asp-encircled Laocoon to Dante's appalling picture of Ugolino and his famished offspring, or the hidden tortures of the Spanish inquisition. The whole mind, during the paroxysm, is wrought up to a pitch of unutterable despair; a spell is laid upon the faculties, which freezes them into inaction; and the wretched victim feels as if pent alive in his coffin, or overpowered by resistless and immitigable pressure."

1 Philosophy of Sleep, 1841, p. 24.

This affection has occupied attention from early times. Hippocrates, for instance, refers to it and to somnambulism in his work on The Sacred Disease (epilepsy): "I have known many persons in sleep groaning and crying out, some in a state of suffocation, some jump* ing up and fleeing out-of-doors, and deprived of their reason until they awaken, and afterward becoming well and rational as before, although they may be pale and weak; and this will happen not once but frequently." Hippocrates thought that nightmare was caused by excessive bile, and dryness of the blood.

Bond, in his essay on the incubus or nightmare, written in 1753, describes the chief characteristics of the attack very well: "The nightmare generally seizes people sleeping on their backs, and often begins with frightful dreams, a violent oppression on the breast, and a total privation of voluntary motion. In this agony they sigh, groan, utter indistinct sounds, and remain in the jaws of death, till, by the utmost efforts of nature, or some external assistance, they escape out of that" dreadful torpid state. As soon as they shake off that vast oppression, and are able to move the body, they are affected with a strong Palpitation, great Anxiety, Languor, and Uneasiness; which symptoms gradually abate, and are succeeded by the pleasurable reflection of having escaped such imminent danger."

Not only does one feel overcome during the attack but often throughout the following day. It is succeeded by a feeling of dread, exhaustion, depression, and there may be headache, and pains in the extremities. As with other unpleasant dreams, nightmare may cast a gloom over all the day's activities. The suffering in the paroxysm is so intense that those who experience it more or less often may dread going to sleep. Instances are recorded of individuals who, rather than go to bed, have spent night after night in their chairs.

There are three pathognomonic symptoms of nightmare, though the intensity of each may vary. The first is agonizing dread; the second, a sense of oppression or weight in the chest; the third, a conviction of helpless paralysis, While in such an unhappy state the individual seems helplessly lost, and a victim of various fiendish tortures. He seems to be buried beneath innumerable heavy rocks; he is lost in a dark, dank, subterranean passage; he is jammed as if in a knot-hole; he is hanging from a precipice; he is pursued by lions, tigers, snakes, witches, or other horrible creatures much beyond his powers of description.

The nature of the dream which is present in nightmare differs with the individual. Some persons when they have nightmare have the same-dream; in others the dream varies. It always produces terror which naturally varies according to the horribleness of the dream. Generally there is no escape once the dream has begun. Some individuals have claimed the power to abort nightmare : for instance, when the nightmare concerned itself with falling from precipices they have voluntarily let go of the precipice, and, it is claimed, this robbed the dream of its terror. Dreams seem real to us and for that reason we are unable to reason out their truth or falsity or to prevent being affected by them. It may be possible in some cases to suggest to one's self before going to sleep that the characters figuring in the dream are false, and so to rob these creatures of much of their fear-inspiring qualities.

Nightmare may occur in any period of sleep, though it is more frequent in the morning, especially after an extra long sleep and when one has gone to bed very fatigued. It is also of common occurrence during the first few hours of sleep. The hypnagogic state is favourable to it, especially in persons who are overfatigued or who are in poor general health. Usually the attacks occur at the same time in each individual.

Probably every one has experienced at some time an attack of nightmare. An occasional attack may not be of grave significance. Some persons have attacks often, and, if for no other reason than that these attacks sap away their physical and mental vitality, should, in place of considering themselves dyspeptics, consult a competent medical psychologist. In persons of low vitality there is danger of shock, or hemorrhage. During the paroxysm, the blood pressure rises, and if the arterial walls are hardened their rupture is possible. The effects of frequent nightmare on the body in general are those of vivid, unpleasant emotions, as indigestion, constipation, nervousness, etc.

Many reasons have been given to explain nightmare. In other days, it was attributed to a spectre of the night (Mara), which seized men in their sleep and deprived them of speech and motion. It was also known as witch-riding. In order to prevent attacks, it was once a custom to hang up hollow stones in stables. In the north of England they were called holy stones. In the middle ages the view prevailed that it was due to male imps (incubi), or female imps (succubi), and because the persons afflicted were supposed to have relations with these evil creatures, they were, often, burned at the stake. How many people have been put to death, often after undergoing horrible torture, because of the belief in possession by evil spirits, is impossible to determine. Mackey, in his Extraordinary Papular Delusions, estimates that during the seventeenth century more than 40,000 people were burned at the stake for witchcraft. And, as most of us know, many peculiar signs were taken as indicative of infection by evil spirits, such as the evil eye, which was, in many cases at least, nothing more than what we call squint today. If a person who betrayed signs of peculiarity showed an anesthetic portion of the skin, this was said to be due to the grasp of the devil, and this portion was called "the devil's claw." Most of the persons who lost their lives in such ways were suffering from hysteria.