while in a sound sleep. He would probably have gone farther but for the fact of his striking his foot against a stone and thus awaking.

The Abbé Richard states that once when coming from the country alone and on foot, sleep overtook him when he was more than half a league from town. He continued to walk, however, though soundly asleep, over an uneven and crooked road.[2]

Even when the most stirring events are transpiring, some of the participants may fall asleep. Sentinels on posts of great danger cannot always resist the influence. To punish a man with death, therefore, for yielding to an inexorable law of his being, is not the least of the barbarous customs which are still in force in civilized armies. During the battle of the Nile many of the boys engaged in handing ammunition fell asleep, notwithstanding the noise and confusion of the action and the fear of punishment. And it is said that on the retreat to Corunna whole battalions of infantry slept while in rapid march. Even the most acute bodily sufferings are not always sufficient to prevent sleep. I have seen individuals who had been exposed to great fatigue, and who had while enduring it met with accidents requiring surgical interference, sleep through the pain caused by the knife. Damiens, who attempted the assassination of Louis XV. of France, and who was sentenced to be torn to pieces by four horses, was for an hour and a half before his execution subjected to the most infamous tortures, with red-hot pincers, melted lead, burning sulphur, boiling oil, and other diabolical contrivances, yet he slept on the rack, and it was only by continually changing the mode of torture, so as to give a new sensation, that he was kept awake. He complained, just before his death, that the deprivation of sleep was the greatest of all his torments.

Dr. Forbes Winslow[3] quotes from the Louisville Semi-Monthly Medical News the following case:

“A Chinese merchant had been convicted of murdering his wife, and was sentenced to die by being deprived of sleep. This painful mode of death was carried into effect under the following circumstances: The condemned was placed in prison under the care of three of the police guard, who relieved each other every alternate hour, and who prevented the prisoner falling asleep night or day. He thus lived nineteen days without enjoying any sleep. At the commencement of the eighth day his sufferings were so intense that he implored the authorities to grant him the blessed opportunity of being strangled, guillotined, burned to death, drowned, garroted, shot, quartered, blown up with gunpowder, or put to death in any conceivable way their humanity or ferocity could invent. This will give a slight idea of the horrors of death from want of sleep.”

In infants the necessity for sleep is much greater than in adults, and still more so than in old persons. In the former the formative processes are much more active than those concerned in disintegration. Hence the greater necessity for frequent periods of repose. In old persons, on the contrary, decay predominates over construction, there is a decreased activity of the brain, the nervous system, and of all other organs, and thus the demand for rest and recuperation is lessened.

The necessity for sleep is not felt by all organic beings alike. The differences observed are more due to variations in habits, modes of life, and inherent organic dispositions, than to any inequality in the size of the brain, although the latter has been thought by some authors to be the cause. It has been assumed that the larger the brain the more sleep was required. Perhaps this is true as regards the individuals of any one species of animals, but it is not the case when species are compared with each other. In man, for instance, persons with large heads, as a rule, have large, well-developed brains, and consequently more cerebral action than individuals with small brains. There is accordingly a greater waste of cerebral substance and an increased necessity for repair.

This is not, however, always the case, as some individuals with small brains have been remarkable for great mental activity.

All animals sleep, and even plants have their periods of comparative repose. As Lelut says:[4]

“No one is ignorant of the nocturnal repose of plants. I say repose and nothing else. I do not say diminution or suspension of their sensibility, for plants have no sensibility. I say diminution of their organic actions—a diminution which is evident and characteristic in all, more evident and more characteristic in some. * * *

“Their interior or vital movements are lessened, the flow of the sap and of other fluids which penetrate and rise in them is retarded. Their more mobile parts—the leaves, the flowers—show by their falling, their occlusion, their inclination that their organic actions are diminished, and that a kind of repose has been initiated, which takes the place of the lying down, which, with animals, is the condition and the result of sleep.”

CHAPTER II.

THE CAUSES OF SLEEP.

The exciting cause of natural and periodic sleep is undoubtedly to be found in the fact that the brain at stated times requires repose, in order that the cerebral substance which has been decomposed by mental and nervous action may be replaced by new material. There are other exciting causes than this, however, for sleep is not always induced by ordinary or natural influences acting periodically. There are many others, which within the strict limits of health may cause such a condition of the brain as to produce sleep.

Authors, in considering sleep, have not always drawn the proper distinction between the exciting and the immediate cause. Thus Macario,[5] in alluding to the alleged causes of sleep, says:

“Among physiologists some attribute it to a congestion of blood in the brain; others to a directly opposite cause, that is, to a diminished afflux of blood to this organ; some ascribe it to a loss of nervous fluid, others to a flow of this fluid back to its source; others again find the cause in the cessation of the motion of the cerebral fibers, or rather in a partial motion in these fibers. Here I stop, for I could not, even if I wished, mention all the theories which have prevailed relative to this subject. I will only add that, in my opinion, the most probable proximate and immediate cause appears to be feebleness. What seems to prove this view is the fact that exhaustive hot baths, heat, fatigue, too great mental application are among the means which produce sleep.”

Undoubtedly the influence mentioned by Macario, and many others which he might have cited, lead to sleep. They do so through the medium of the nervous system—causing a certain change to take place in the physical condition of the brain. We constantly see instances of this transmission of impressions and the production of palpable effects. Under the influence of fatigue, the countenance becomes pale; through the