PREDISPOSING CAUSES OF SLEEP. 289 banished, or rendered imperfect. But if, occasionally, under circumstances of such inactivity of the voluntary muscles, the mind undergoes long and severe exercise, the system is found to require as much sleep, if not more sleep, than if the muscular system, and not the mind, had been at work. And if such an amount of sleep is not enjoyed, it were well to pause, and endeavour to ensure it, by sacrificing some of the next day's moments to the various means by which sleep may be promoted; or, ere long, the mind will become less and less capable of profitable effort: the tired steed will answer to the whip and spur no longer. Habit influences in some degree the amount of sleep that is required. It should be said, however, that it is never well to withhold any of the revenue that is justly due to the drowsy god. A man may accustom himself to take so little sleep, as to be greatly the loser thereby in his waking moments. It may be commonly observed, that those persons who spend less time in sleep, than is usually found needful by others of the same age and strength and occupation, consume a much larger portion of their days than others do, in a kind of dreamy vacancy, a virtual inactivity of mind and body. The hours expended in sleep are not the only hours that might be justifiably deducted from the sum total of the life, as having been lost to it: numbers of moments are daily spent in an absolute inaction of mind and body; and sleep cannot be robbed of its dues, without adding largely, and in greater proportion than the VOL. II. time habitually stolen from the sleep, to that which is wasted in such waking reveries. In order that the mind may have the power of undergoing trying and exhausting labour, that it may continue in the full possession of its capabilities, that it may continue to be undulled and unblunted by such wear and such use, an amount of sleep must be allowed, which is proportionate to the severity of such work, to the engrossing and expending nature of the mind's employment. The nights may be robbed of the hours of sleep; and the time so stolen may be devoted to toil of mind or of body; but the endurance by the system of the undue waste and imperfectly restored balance of the vital force, even if somewhat protracted by the strength of the constitution, or if prolonged somewhat by the energy of a determined will, or by the spur of a great necessity, or by the desired goal of a great ambition or darling hope, must be short-lived. The system cannot be robbed of its sleep without a corresponding disturbance and derangement of the functions; the power and the equilibrium of the vital forces will become so far affected, as to involve disordered action; and thus indirectly by forming part of the common organism, and directly by the diminished tension of the vital forces which supply the sensorium itself, the mind will become unable to continue its exertions. Many an ardent and hopeful aspirant for collegiate distinctions, many an anxious labourer for professional eminence, is thrown away his hopes in thus vainly struggling heat the system of this great requirement. PREDISPOSING CAUSES OF SLEEP. 291 I have said that the constitution of individuals modifies the amount of sleep which they require. The delicate-fibred, the feeble, and the nervous, require more sleep than the muscular, the powerful, and the unailing. The debilitated offspring of the sedentary, the voluptuous, the scantily fed, or the aged, require more sleep than the vigorous child of the active, the temperate, the plainly but well fed, and the youthful. It has been observed, that the health of an individual greatly modifies the amount of sleep which he stands in need of. The more weakly, the more languid, or the more irritable, the state of the system, the greater the amount of sleep that is commonly needed. The more lethargic, or the more strong the individual, the less of sleep that should be taken. The kind of disease that may be present, is often found to influence the amount of sleep which seems to be needful; but generally, the diseases which interfere the most with the dues of the system as to sleep, are the most likely to lead to irreparable injury to the health. In some cases, disordered action interferes with the sleep to the extent of fearfully aggravating the wearing effects of the disease, and increasing the risk of a fatal issue to the case in a corresponding degree. The restoration of a sufficient and perfect sleep, is often the first indication of the diminution of morbid action and the approach of convalescence. The kind of food that is made use of, modifies the amount of sleep which is required. Animal food renders more sleep necessary than vegetable food; and those persons who sleep much-too much in proportion to their constitutional powers, and to the amount of exercise of mind or body that is taken, and in whom this cannot be attributed to temporary influences or actual disease-may do well to think whether this may not be owing to the quantity of animal food which they consume; and should there appear to be some reason for such an opinion, may wisely try the effect of diminishing the proportion of animal food consumed by them. In extreme cases of this kind, they may be wisely directed to make use of an exclusively vegetable diet for a time. It is a no less useful observation, that many cases of defective sleep, particularly in the invalided, are more or less relievable by the use of a larger proportion of animal food : supposing such a higher dietary to be otherwise unobjectionable. The unnecessary indulgence in the use of malt liquors, or of wine or spirits, is a common cause of an excessive amount of sleep. This is truly stealing from one's days, and recklessly throwing such time into the waters of an unrequiting oblivion. Excessive sleep, moreover, induces torpor and derangement of the bodily functions, and debilitates the system in the same proportion. The effect of excessive sleep on the mental faculties is no less serious. It dulls the sensibilities, and weighs down, warps, and impairs the imagination, the judgment, and the memory. The time required for sleep, evidently varies much; seven or eight hours may perhaps be said to be the usual average;-the young, and the feeble, and the PREDISPOSING CAUSES OF SLEEP. 293 ailing, requiring more, and some strong and healthy adults requiring less. Usually, less sleep is required in summer than in winter, in this climate. In warm climates, or during very hot weather, the vital forces become so rapidly expended, and their equilibrium is so soon disturbed to such a degree, that the system cannot continue its labours without discomfort and disadvantage, during the sixteen or seventeen hours; and the same remark applies to invalids and very delicate and feeble individuals, in any climate. Under such circumstances, a midday sleep seems to be useful and necessary. The night time is evidently intended as the proper period for sleep; and the adage which tells us that "early to bed and early to rise" are conducive to health, is for the most part, if received with some qualifications, sound and good. In these higher latitudes, to rise with the sun at the different times of the year, would interfere with the regularity of habit, by a moderate attention to which the health of mankind is known to be so much promoted, whether in regard to food, or exercise, or sleep, &c. Moreover, in the earlier hours of morning, at all times of the year, the air is apt to be charged with the dampness and probable impurity of the terrestrial exhalations, which must render exposure to the air at such time somewhat less wholesome. This observation would, however, seldom apply to more than the first or second hour after sunrise. Generally speaking, the going to bed at such hours of the evening as will have left an adequate time for sleep before the hours |