Laziness takes nine,
And wickedness eleven.”
The error into which these and others have fallen arises not only from the fact that in this, as well as in other things, every man is a law to himself, but from the varying amount required in each individual case at different times, depending upon the amount of renovation required by the nervous and muscular systems. John Wesley, the distinguished founder of Methodism, who attained the age of eighty-eight, and who could command sleep on horseback, says very properly, in some curious remarks which he has left upon sleep, that no one measure will do for all, nor will the same amount of sleep suffice even for the same person at all times. A person debilitated by sickness requires more of “tired nature’s sweet restorer” than one in vigorous health. More sleep is also necessary when the strength and spirits are exhausted by hard labor or severe mental efforts. Whatever may be the case with some few persons, of a peculiar constitution, it is evident that health and vigor can scarcely be expected to continue long without six hours’ sleep in the four-and-twenty. Wesley adds that during his long life he never knew any individual who retained vigorous health for a whole year, with a less quantity of sleep than this.
It is said that women, in general, require more sleep than men. This is doubtful: it is certain, at least, that women endure protracted wakefulness better than men. The degree of muscular and mental exertion to which the male is accustomed would seem to indicate that a longer period of rest ought to be required by him to admit of the necessary restoration of excitability. In infancy and youth, where the animal functions are extremely active, the necessity for sleep is greatest; in mature age, where time is more valued and cares are more numerous, it is less indulged; whilst the aged may be affected in two opposite ways; they may be either in a state of almost constant somnolency, or their sleep may be short and light.
There are some remarkable cases on record of deviations from the customary amount of sleep, making a “bed shorter than for an ordinary man to stretch himself upon, and a covering narrower than he can wrap himself in,” capacious enough for persons of very active habits in their waking hours. Many persons have reached advanced age without ever having had more than one or two hours’ sleep out of the twenty-four. There is one case of a man who, throughout his whole life, never slept more than fifteen minutes at one time. General Pichegru informed Sir Gilbert Blane that, in the course of his active campaigns, he had for a whole year not more than one hour of sleep in the twenty-four hours. Frederick of Prussia and Napoleon, as a general thing, only devoted three or four hours to sleep.
One can scarcely conceive a more horrible mode of torture than the Chinese plan of condemning criminals to death by preventing sleep. The victim is kept awake by guards alternately stationed for the purpose. His sufferings last from twelve to twenty days, when death comes to his relief.
The influence of habit in promoting or preventing sleep is remarkable. Those accustomed to the tranquillity of rural districts are excessively annoyed by the din of the carriages on the paved thoroughfares of a large city. It is said, on the other hand, that those who live near the cataracts of the Nile cannot sleep at a distance from them, owing to their having become accustomed to the noise, the stimulus of which upon the ear they lack. Some persons can only sleep in the dark; we knew a woman who slept habitually with a candle burning in her bedroom, and who invariably awoke if the light went out. Some of the soldiers of Bonaparte’s army would sleep, after extreme fatigue and exhaustion, on the ground by the side of a twenty-four pounder which was constantly firing. Some boys slept from fatigue on board of Nelson’s ship, at the battle of the Nile. We have heard of a boiler-maker who could go to sleep in a boiler while the workmen were constantly hammering the rivets.
Sleep can persist with the exercise of certain muscles. Couriers on long journeys nap on horseback; and coachmen, on their boxes. Among the impressive incidents of Sir John Moore’s disastrous retreat to Corunna, in Spain, not the least striking is the recorded fact that many of his soldiers steadily pursued their march while fast asleep. Burdach, however, affirms that this is not uncommon among soldiers. Franklin slept nearly an hour swimming on his back. An acquaintance of Dr. D., travelling with a party in North Carolina, being greatly fatigued, was observed to be sound asleep in his saddle. His horse, being a better walker, went far in advance of the rest. On crossing a hill, they found him on the ground, snoring gently. His horse had fallen, as was evident from his bruised knees, and had thrown his rider on his head on a hard surface, without waking him.
Animals of the lower orders obey peculiar laws in regard to sleep. Fish are said to sleep soundly; and we are told by Aristotle that the tench may be taken in this state, if approached cautiously. Many birds and beasts of prey take their repose in the daytime. When kept in captivity, this habit undergoes a change,—which makes us doubt whether it was not the result of necessity, which demanded that they should take advantage of the darkness, silence, and the unguarded state of their victims. In the menagerie at Paris, even the hyena sleeps at night, and is awake by day. They all, however, seek, as favoring the purpose, a certain degree of seclusion and shade, with the exception of the lion, who, Burdach informs us, sleeps at noonday, in the open plain; and the eagle and condor will poise themselves on the most elevated pinnacle of rock, in the clear blue atmosphere and dazzling sunlight. Birds, however, are furnished with a winking membrane, generally, to shelter the eye from light. Fish prefer to retire to sleep under the shadow of a rock or a woody bank. Of domestic animals, the horse seems to require least sleep; and that he usually takes in the erect posture.
Birds that roost in a sitting posture are furnished with a well-adapted mechanism, which keeps them firmly supported without voluntary or conscious action. The tendon of the claws is so arranged as to be tightened by their weight when the thighs are bent, thus contracting closely and grasping the bough or perch. In certain other animals which sleep erect, the articulations of the foot and knee are described by Dumeril as resembling the spring of a pocket-knife, which opens the instrument and serves to keep the blade in a line with the handle.