more composed; we think coolly, clearly, rationally, and can often comprehend with ease what baffled us on the previous night. One or two other points remain to be noticed. On awaking, the eyes are painfully affected by the light, but this shortly wears away, and we then feel them stronger than when we went to bed. The muscular power, also, for a few seconds, is affected. We totter when we get up; and if we lay hold of any thing, the hand lacks its wonted strength. This, however, as the current of nervous energy is restored throughout the muscles, immediately disappears; and we straightway possess redoubled vigour. On examining the urine, we find that it is higher in its colour than when we lay down. The saliva is more viscid, the phlegm harder and tougher, the eyes glutinous, and the nostrils dry. If we betake ourselves to the scale, we find that our weight has diminished in consequence of the nocturnal perspirations; while, by subjecting our stature to measurement, we shall see that we are taller by nearly an inch than on the preceding night. This fact was correctly ascertained in a great variety of instances by Mr. Wasse, Rector of Aynho in Northumberland; and is sufficiently accounted for by the intervertebral cartilages recovering their elasticity, in conse quence of the bodily weight being taken off them during the recumbent posture of sleep. Such are the leading phenomena of sleep. With regard to the purposes which it serves in the economy, these are too obvious to require much detail. Its main object is to restore the strength expended during wakefulness; to recruit the body by promoting nutrition and giving rest to the muscles; and to renovate the mind by the repose which it affords the brain. Action is necessarily followed by exhaustion; sleep by checking the one restrains the other, and keeps the animal machine in due vigour. Mr. Carmichael supposes sleep to be the period when assimilation goes on in the brain. In this respect, I believe that the brain is not differently situated from the rest of the body. There, as elsewhere, the assimilative process proceeds both in the slumbering and in the waking state; but that it is only at work in the 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, colours, 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 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 sleeptalking, 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 stag-hounds, weary with the chase, And urged in dreams the forest race From Teviot-stone to Eskdale moor." Lay of the Last Minstrel, |