up, and sometimes to be pendent, according to the nature and genus of the plant, in order to protect the flowers, buds, or young stems.—This period of rest is absolutely necessary to vegetables; their irritability being exhausted by the light and warmth of the day. The circulation of the sap, also, is less rapid in their dormant state; from which circumstance Dr. Darwin conjectures that, as there is less wasted during their inactivity, it is probable that young plants may thrive more rapidly, in the same manner as animals are believed, during their youth, to grow faster when in a state of rest, than in that of exercise.
SLEEPING, is that state of the body, in which the animal functions are suspended.
The proper duration of sleep must be regulated, according to the different constitutions and ages of individuals. Thus, in the first six months of its existence, an infant may be allowed to sleep the greater part of the day; but, after that period, it will be necessary to abridge this indulgence, gradually, with the advance of years. For children, from the age of seven years to that of adolescence, and also for aged persons, eight or nine hours of nightly rest will be required; but for adults, and those who are not obliged to fatigue themselves with mental or bodily exertions, six or seven hours will be sufficient.
The proper hour for retiring to sleep, having already been stated under the article Bed-time, we shall conclude the subject with a few remarks, on the practices occasionally observed in the nursery.
Children, and even infants, are sometimes prevented from going to sleep, by a variety of circumstances, which maternal solicitude only can discover: we conceive it, therefore, our duty, to caution parents and conscientious nurses, against employing artificial means, and particularly opiates or narcotic substances, whether externally or internally, with a view to lull the child to sleep; as these detestable remedies tend to stupify the latent faculties, and to weaken the intellect of such tender constitutions. Equally absurd and injudicious is the practice of terrifying young people to sleep by threats; or of wheedling them by promises; for, in the former case, they early acquire sentiments of disgust and hatred, which have the most baneful influence on their subsequent conduct: in the latter, they become selfish; and, at length, it will be requisite to pay them for sleeping.
SLEEP-WALKING, or Somnambulism, a remarkable disorder, proceeding from an inflamed or disturbed imagination; and in which the patient's eyes are widely open; though he can discern no object: at the same time, he has the power of recollection ; directs his walks to some particular spot; and, after arriving at the end of his nocturnal journey, he retires to bed, apparently composed; and sleeps calmly during the remainder of the night.
Dr. Cullen considers this affection as an active species of the Nightmare (oneirodynia activa), and consequently as originating from the same source.
The causes, however, which have generally been supposed to induce somnambulism, are: a very plethoric state of the blood, especially that towards the head; a disturbed ima-
