If the hypnotic sleep has been profound, it may be necessary twice or thrice to repeat the order to awake, and even to enforce it by fanning the patient, or blowing gently upon his eyes; but the simple command is nearly always sufficient.

There certainly is nothing mysterious in all this, and Liebeault seemed to take pleasure in making his whole mode of treatment clear to any serious inquirer, and in giving the rational explanation of everything that he did. He directed the patient to fix his attention on a certain point in order to strain the accommodation of the eyes and tire the sight. The effect of the strain is to cause dilatation of the pupils and consequent dimness of vision. The feeling of heaviness in the eyelids results from the fatigue of keeping them open in a strained position, and the assertion that the eyes are becoming tired and the sight dim is therefore founded on physiological data, and is not guesswork. The eyes being tired, the natural impulse is to close them, and this act calls up a previous association of ideas connected with fatigued or confused sight. That association points to sleep, towards which the patient is rapidly led, aided by the monotonous tones of the operator suggesting it to him, and by his mind being free from all disturbing thoughts, and his nerves from all external stimuli. He falls asleep, in fact, much in the same manner as one does when reading a dull book or listening to a not too brilliant discourse.

Maury, in his well-known book on sleep and dreams, says: ' The less the mind is occupied with ideas, the more easily can the thoughts be directed into any given channel. If nothing claims our notice or holds our attention, the cerebro-spinal system, for want of that gentle stimulation which is necessary to it, falls into a state of semi-torpor inseparable from atony of the nervous system.'

In the chapter on sleep in Carpenter's ' Physiology' various conditions are mentioned as being favourable to it, one being the desire for it, another the expectation of it. We expect, from previous experience, that if we lie down in a certain place, sleep will follow. The faculty of imitation helps to bring it about; when we see others dozing, we naturally incline to follow their example, and at night the consciousness that all around us are asleep disposes us to seek the same condition. Talking about sleep is apt to induce somnolence, just as talking about food may provoke hunger. And a monotonous sound, such as a droning voice of a speaker, or the breaking of gentle waves upon the seashore, tends to encourage slumber. Thus it will be seen how closely the artificial method I have described follows natural rules. This method may fail, just as we may fail to obtain natural sleep, or may battle it off should we desire to remain awake. If a patient wishes to resist the somnolent influence, he can do so by refusing to concentrate his thoughts, or by inducing some physical discomfort - for instance, by placing himself in an uneasy position.

Strong emotion, such as anger or fear, will prevent the hypnotic sleep; so will severe pain, hunger, thirst, and, indeed, anything which preoccupies the mind or agitates the nervous system. Constitutional idiosyncrasies affect this just as they affect the normal sleep. The naturally restless sleeper will be restless, and he who commonly goes off as soon as his head touches the pillow will quickly succumb to the hypnotic influence. The extent to which a person is influenced varies according to his mental and physical condition. If he is of restless and flighty temperament, it may be impossible to fix his attention for even the few minutes that are necessary, and no effect is produced - except, perhaps, an inclination on his part to treat the whole affair as a jest, and a consequent irritation on the part of the doctor. But in ordinary cases some effect is certainly produced, if not on a first visit, still on subsequent ones. This effect will vary in various patients, some feeling only a heaviness and torpor, with a disinclination to open the eyes, while others fall into a more or less profound sleep, or into a state of somnambulism.

Liebeault divides the sleep into six different stages, * but as these really merge imperceptibly into each other, the division is purely arbitrary, and is made for convenience in classification. They may be shortly summed up as: (1) Light sleep; (2) profound sleep; (3) somnambulism.

The first and second stages closely resemble and are analogous to ordinary sleep; but the third is sui generis, and will require a few words later on. Though it is analogous to natural sleep, there is one very important fact which shows that the conditions are not identical. If an ordinary sleeper is spoken to, he is generally aroused by the stimulating effect of the sound conveyed to the brain through the auditory nerves, but one in the hypnotic state may be talked to without being disturbed; the effect will, on the contrary, be soothing. He is, in fact, en rapport with the outer world, though only to a limited extent, whereas in natural sleep he is en rapport only with his own consciousness.

Upon this difference depends the possibility of applying curative suggestion. Carpenter (op. cit.) says that the very closure of the eyes renders the other senses more acute; and we have seen that the inactivity of one sense is nearly always compensated for by increased sensitiveness of the others. Now, in the hypnotic state all the senses are more or less torpid and in abeyance until called into play by the operator. Physiologists suppose that during activity the nerve centres are continually discharging nervous energy in all directions, in response to stimulating impressions received through the senses; but in sleep a state of inactivity is induced, and the nervous force accumulates in the brain cells. Natural sleep comes as a consequence of fatigue, and because the store of nerve energy is nearly or entirely exhausted. During its continuance a fresh store of nerve energy will be laid up, and if it be undisturbed, the store will go on increasing until sufficient is acquired for complete nerve recuperation. This point attained, the sleeper, if in good mental and bodily health, will awake naturally, and feel no further desire for slumber.

But as the hypnotic state may be produced at any time in the twenty-four hours, and long before any perceptible inroad has been made on the store of nerve energy laid up during the previous natural sleep, it follows that during the artificial sleep there may be great accumulation and excess of energy. All this can be concentrated and directed into any channel the physician may desire; and this concentrated and directed nerve force must naturally affect the system more powerfully than any ordinary nervous impression. This fact may explain the rapid production of congestion to a given part (alluded to in Chapter V (Psycho-Therapeutics Not An Exclusive System Of Treatment).), and also the sensation of warmth usually experienced in any part to which the attention has been drawn. It also accounts for the success of the treatment in some cases of paralysis of long standing.

* See Appendix, p. 389, note 8.