Constitutionally some individuals require but very little sleep. Bonaparte, Pichegru, and Scipio may be mentioned among many others, in whom the recuperative energy of the system was sufficient to restore its equilibrium in much less time than is ordinarily required.

It would appear from the result in cases where sleep is too long withheld, that, primarily, the body receives and sustains a deleterious shock, and the mind becomes affected by the impaired physical condition. Sleep is a phenomenon of the organs of external relation; established for the resuscitation of the voluntary part of our physical constitution, leaving the organic system unchanged, except in its relation with the organs of animal life. Irritability and intensity of mental action increase with wakefulness, and unless subdued by sleep they will goad the brain into disease, terminating in madness. For

"Who can wrestle against sleep? - yet Is that giant very gentleness."

It is reasonable to infer, that the mind suffers because connected with a sleepless body - not because it does not sleep, for it is immaterial and cannot rest.

When we come to speak of stimuli operating on the nerves of external sense during the stages of slumber and dreaming, we shall regard the fact* that some of the nerves of sense have more intimate relation with the organs of mind than others. The optic, for instance, has its origin direct from the brain itself, and is in more perfect communion with the intellectual being than any other inlet to the mind. In truth it is the "Window of the soul."

Cabanis says that the senses fall asleep in a regular series of periods, each having its proper time, so that some of them are passive, while others are still active. And most physiologists agree with him that the organ of sight is the first to sleep. Whether this be so, may be questionable; but it undoubtedly is the most important one to render inactive that sleep may follow, and the only organ of sense subject to the will; consequently, it is, through volition, closed to its natural stimulus. But the closure of the lids does not preclude the influence of light absolutely, for through the lids an impression of light more or less strong, is transmitted. Persons unaccustomed to sleep with a light in their dormitory, find themselves much troubled to obtain sleep under its influence; and when obtained, they are unusually disturbed by dreams more vivid than are common with them under other circumstances. The only reasonable method to account for this result is, that although their eyes are closed, still a sufficient amount of light is admitted through the translucent palpebra, to stimulate the mind with ideas of vision and their associate operations.

Of all the senses, the influence of sight upon the mind is the most difficult to control; and it is the only sense upon which volition directly operates. The other senses (possibly of smell excepted) have their connexion with the brain through the medulla oblongata, and their impressions may fall en the mind in a modified degree. It is doubtful whether we attempt to close any other organ of external sense against its ordinary stimulus.

The organ of hearing, if affected at all by volition, is by the power of abstracting the mind from outward impressions; but to prevent the vibrations of sound falling upon the tympanum is impossible by any effort of the will; therefore, whatever power we may possess in regard to this sense, as well as smell, taste and touch, must depend upon the faculty of concentrating the mind upon subjects unconnected with their impressions. The ear probably transmits its impressions to the mind much longer than any other external organ.

Takes a strange turn, and performs two offices at the same time, being directed to the rhyme on one hand, and something else on the other; and it will be found that the hold it has of the former is always much weaker than, of the latter. The great secret is, by a strong effort of the will, to compel it to depart from the favorite train of thought into which it has run, and address itself solely to the verbal repetition of what is substituted in its place. If this is persevered in, it will generally be found to succeed; and I would recommend all those who are prevented from sleeping in consequence of too active a flow of ideas, to try the experiment. It has been already remarked, the more the mind is brought to turn upon a single impression, the more closely it is made to approach to the state of sleep, which is the total absence of all impression."

Gardener's directions, as advocated by Dr. Binns in his "Anatomy of Sleep," are that the person "turn on his right side, place his head comfortably on the pillow, so that it exactly occupies the angle a line drawn from the head to the shoulder would form, and then slightly closing his lips, take rather a full inspiration, breathing as much as he possibly can through the nostrils. This, however, is not absolutely necessary, as some persons breathe always through their mouths during sleep, and rest as sound as those who do not. Having taken a full inspiration, the lungs are then to be left to their own action - that is, the respiration is neither to be accelerated nor retarded too much ; but a very full inspiration must be taken. The attention must now be fixed upon the action in which the patient is engaged. He must depict to himself that he sees the breath passing from his nostrils in a continuous stream, and the very instant that he brings his mind to conceive this apart from all other ideas, consciousness and memory depart; imagination slumbers; fancy becomes dormant; thought ceases; the sentient faculties lose their susceptibility; the vital or ganglionic system assumes the sovereignty; and as before remarked, he no longer wakes, but sleeps. For the instant the mind is brought to the contemplation of a single sensation, that instant the sensorium abdicates the throne, and the hypnotic faculty steeps it in oblivion."

Sleep may be induced by attentively listening to the click of a clock, and by attempts to repeat the alphabet backwards, not an easy task to those unaccustomed to it. But although so many rules for the benefit of the sleepless have been promulgated, still it will be found that each individual requires a formula adapted to his own particular temperament, and which, from necessity, he will ultimately discover for himself.

Essentially, there is no difference between these several suggestions. They all depend upon some plan whereby the mind is ultimately brought to a single idea, monotonous in character, and there steadily held, until sleep is induced by a normal act of our constitution. The mind undoubtedly always arrives at just such a crisis, whether we will it or not, before sleep takes possession of the sensational organs, and then it is again free to rove through its diversified operations.

Divisions

Various distinctions have been made in the nature of sleep, based upon preconceived theories of its cause; and they are treated of under the heads of natural and morbid: - but this division is dependent upon the proximate cause - not upon its natural phenomena. The exercise of the voluntary muscular texture, and. the action of the mental organs, when carried to that degree of fatigue which induces sleep, is termed a natural, and that prostration arising from the use of narcotics terminating in sleep, is called a morbid condition: - but the veiled essence of sleep is the same, whether induced by natural and healthy means, or produced by morbid influences. In either case, the external phenomenon of sleep is involuntary abstractedness to surrounding objects, whose ordinary influences are not, for the time being, transmitted to the sensorium, but the recollection of them may, nevertheless, act with great power upon our sleeping existence.