The enjoyment of comfortable and undisturbed sleep, is certainly to be ranked amongst the greatest blessings which heaven has bestowed on mankind; and it may be considered as one of the best criterions of a person enjoying perfect health. On the contrary, any disturbance which occurs in the enjoyment of this invaluable blessing, may be considered a decisive proof of some derangement existing in the animal economy, and a consequent deviation from the standard of health. Indeed it is astonishing how slight a deviation from that standard may be perceived, by paying attention to the circumstance of our sleep and dreams. This may be more clearly demonstrated by attending carefully to the state of persons on the approach of any epidemic fever or other epidemic disease, and indeed of every kind of fever, as I have repeatedly witnessed; when no other signs of a deviation from health could be perceived, the patient has complained of disturbed rest and frightful dreams, with Night-Mare, &c. Hence the dread which the vulgar, in all ages and countries, have had of what they call bad dreams; experience having proved to them, that persons, previously to being attacked with some serious or fatal malady, had been visited with these kind of dreams. For this reason they always dread some impending calamity either to themselves or others, whenever they occur; and, so far as relates to themselves, often not without reason. Frightful dreams, however, though frequently the forerunners of dangerous and fatal diseases, will yet often occur when the disturbance of the system is comparatively trifling, as they will generally be found to accompany every derangement of the digestive organs, particularly of the stomach, of the superior portion of the intestinal canal, and of the biliary system. Children, whose digestive organs are peculiarly liable to derangement, are also very frequently the subjects of frightful dreams, and partial Night-Mares; which are frequently distressing enough to them. They are still more so to grown up people, as they generally arise from a more serious derangement of the system. Those who are subject to them will agree with me in opinion, that they are by no means to be ranked amongst the lesser calamities to which our nature is liable.

There are many persons in the world to whom it is no uncommon occurrence, to rise from their bed in the morning more wearied and exhausted, both in mind and body, than when they retired to it the evening before: to whom sleep is frequently an object of terror rather than comfort, and who seek in vain for relief from the means usually recommended by Physicians. To such persons I dedicate this little work; for their information I have laid down, in as clear terms as the subject will admit, the history of those diseases, which, by depriving us of the benefit of sleep, and driving rest from our couch, often render life itself miserable, and lay the foundation of formidable, and sometimes of fatal diseases. Amongst those affections which thus break in upon our repose, the most formidable and the most frequent is the disease called Night-Mare; the history of which, with its various modifications, I have endeavoured to give with as much accuracy as possible, and have attempted also to investigate its nature and immediate causes, as well as to point out the best mode of obtaining relief. Very little assistance could be obtained in this undertaking, from the writings of modern Physicians, who have paid little or no attention to it: those of the sixteenth and seventeenth centuries, seem to have well understood both its causes and cure, but differed much amongst themselves respecting its nature, as will ever be the case when we attempt to reason on any subject which is above our comprehension. I have availed myself of all the light which these illustrious men could throw upon the subject, which is not a little; but my principal information respecting it has arisen from a personal acquaintance with the disease itself, for a long series of years, having been a victim to it from my earliest infancy. I have never met with any person who has suffered to so great an extent from this affection, or to whom it was become so habitual. To eradicate thoroughly a disease so deeply rooted and of so long duration, cannot be expected: but I have so far succeeded as to bring it under great control, and to keep myself free from its attacks for several months together; or indeed scarcely ever to be disturbed by it at all, but when I have deviated from those rules which experience has proved to be sufficient to secure me from all danger of it.

The various kinds of disturbed sleep taken notice of in this little work, are all so many modifications of Night-Mare, and may be all remedied by observing the rules here laid down, as they will be found to originate from one or other of the causes here specified. The regimen and treatment I have recommended are directed to the root of the disease, that is, to the hypochondriac or hysteric temperament; for Night-Mare, disturbed sleep, terrific dreams, &c. may be considered only as symptoms of great nervous derangement, or hypochondriasis, and are a sure sign that this disease exists to a great extent. Thus, while the patient is seeking, by the means recommended, to get rid of his Night-Mare, he will find his general health improving, and the digestive organs recovering their proper tone.