brain during sleep analogy forbids us to admit. So long as circulation continues, a deposition of matter is going on; and circulation, we all know, is at work in the brain as in other organs, whether we be asleep or awake. According to Richerand, one of the great purposes served by sleep, is to diminish the activity of the circulation, which a state of wakefulness has the invariable effect of increasing. "The exciting causes," he observes, "to which our organs are subject during the day, tend progressively to increase their action. The throbbings of the heart, for instance, are more frequent at night than in the morning; and this action, gradually accelerated, would soon be carried to such a degree of activity as to be inconsistent with life, if its velocity were not moderated at intervals by the recurrence of sleep." To detail the beneficent purposes served by sleep in the cure of diseases, as well as in health, would be a work of supererogation. They are felt and recognised by mankind as so indispensable to strength, to happiness, and to life itself, that he who dispenses with that portion of repose required by the wants of nature, is in reality curtailing the duration of his own existence. CHAPTER III. DREAMING. IN perfect sleep, as we have elsewhere stated, there is a quiescence of all the organs which compose the brain; but when, in consequence of some inward excitement, one organ or more continues awake, while the remainder are in repose, a state of incomplete sleep is the result, and we have the phenomena of dreaming. If, for instance, any irritation, such as pain, fever, drunkenness, or a heavy meal, should throw the perceptive organs into a state of action while the reflecting ones continue asleep, we have a consciousness of objects, colors, or sounds being presented to us, just as if the former organs were actually stimulated by having such impressions communicated to them by the external senses;* while in consequence of the repose of the reflecting organs, we are unable to rectify the illusions, and conceive that the scenes passing before us, or the sounds that we hear, have *This internal stimulation of particular organs without the con currence of outward impressions by the senses, is more fully stated under the head of Spectral Illusions. a real existence. This want of mutual co-operation between the different organs of the brain accounts for the disjointed nature, the absurdities, and incoherencies of dreams. Many other doctrines have been started by philosophers, but I am not aware of any which can lay claim even to plausibility; some, indeed, are so chimerical, and so totally unsupported by evidence, that it is difficult to conceive how they ever entered into the imaginations of their founders. Baxter, for instance, in his "Treatise on the Immortality of the Soul," endeavors to show that dreams are produced by the agency of some spiritual beings, who either amuse, or employ themselves seriously, in engaging mankind in all those imaginary transactions with which they are employed in dreaming. The theory of Democritus and Lucretius is equally whimsical. They accounted for dreams by supposing that spectres, and simulacra of corporeal things constantly emitted from them, and floating up and down in the air, come and assault the soul in sleep. The most prevailing doctrine is that of the Cartesians, who supposed that the mind was continually active in sleep; in other words, that during this state we were always dreaming. Hazlitt, in his "Round Table," has taken the same view of the subject, and alleges, that if a person is awakened at any given time and asked what he has been dreaming about, he will at once be recalled to a train of associations with which his mind had been busied previously. Un fortunately for this theory, it is not sustained by facts; experiments made on purpose having shown that, though in some few instances, the individual had such a consciousness of dreaming as is described, yet in the great majority he had no consciousness of any thing of the kind. The doctrine, therefore, so far as direct evidence is concerned, must fall to the ground; and yet, unsupported as it is either by proof or analogy, this is the fashionable hypothesis of the schools, and the one most in vogue among our best metaphysical writers: There is a strong analogy between dreaming and insanity. Dr. Abercrombie defines the difference between the two states to be, that in the latter the erroneous impression, being permanent, affects the conduct; whereas in dreaming, no influence on the conduct is produced, because the vision is dissipated on awaking. This definition is nearly, but not wholly correct; for in somnambulism and sleep-talking, the conduct is influenced by the prevailing dream. Dr. Rush has, with great shrewdness, remarked, that a dream may be considered as a transient paroxysm of delirium, and delirium as a permanent dream. Man is not the only animal subject to dreaming. We have every reason to believe that many of the lower animals do the same. Horses neigh and rear, and dogs bark and growl in their sleep. Probably, at such times, the remembrance of the chase or the combat was passing through the minds of these creatures; and they also not unfrequently manifest signs of fear, joy, playfulness, and almost every other passion.* Ruminating animals, such as the sheep and cow, dream less; but even they are sometimes so affected, especially at the period of rearing their young. The parrot is said to dream, and I should suppose some other birds do the same. Indeed the more intellectual the animal is, the more likely it is to be subject to dreaming. Whether fishes dream it is impossible to conjecture: nor can it be guessed, with any thing like certainty, at what point in the scale of animal intellect, the capability of dreaming ceases, although it is very certain there is such a point. I apprehend that dreaming is a much more general law than is commonly supposed, and that many animals dream which are never suspected of doing so. Some men are said never to dream, and others only when their health is disordered: Dr. Beattie mentions a case of the latter description. For many years before his death, Dr. Reid had no consciousness of ever having dreamed; and Mr. Locke takes notice of a person who never did so till his twenty-sixth year, when he began to dream in consequence of having had a fever. It is not impossible, however, but that, in these cases, the individuals may have had dreams from the same * "The stag-hounds, weary with the chase, From Teviot-stone to Eskdale moor." Lay of the Last Minstrel. |