What has already been said should suffice to show the close connection between sleep and hypnosis, a subject upon which no mean light is thrown by the close resemblance of posthypnotic suggestions to the after-effects of many a dream.

Although, as we have seen, deep hypnosis and ordinary sleep are closely related, and especially as regards dreams stand very close to one another, we must not therefore accept the identity of sleep and hypnosis. Dreams are only one symptom of sleep; we cannot, consequently, regard a comparison of dreams and suggested hallucinations as sufficient to demonstrate identity. I believe that even in deep hypnotic states we have clear grounds for concluding that the condition is not identical with sleep; for in order to assert an unconditional identification we must take into consideration not only the psychological image, but also the physiological symptoms. Now, we know that during sleep the pulse, the respiration, and other bodily functions are changed, and exhibit a greater regularity and prolongation. If we do not find this in deep hypnosis, it is a proof that the physiological condition in hypnosis is not identical with that in sleep. Francke finds, indeed, that pulse, respiration, and skin secretion show greater regularity, but his observations are not convincing, since he tells us nothing more definite concerning the other symptoms of hypnosis as he observed it. In any case, however, Francke saw a remarkable resemblance between the curves of sleep and hypnosis.

I have only seen in a few cases of hypnosis the slowing of the respiration and pulse observed in sleep; I believe therefore that the state in which this is not observed cannot, on the grounds already mentioned, be identified with sleep. Certain pathological conditions argue an even wider separation of sleep and hypnosis. The spasm of chorea and the tremulous movements in paralysis agitans cease in ordinary sleep. I have hypnotized patients suffering from these diseases without causing the movements or tremors to cease. Certainly other observers state that they have seen the spasm of chorea stop in hypnosis, and this circumstance is utilized as a proof of the identity of hypnosis and sleep; still, that is not sufficient. I have never asserted that choreatic twitches can never be brought to a standstill in hypnosis. My remark refers to typical chorea at its acme. In such a case I have never seen the spasms cease in hypnosis, any more than I have seen the tremors of palsy stop in the numerous cases in which I have attempted to bring hypnotic influence into play. That the spasm of chronic chorea, or of an acute attack which is subsiding, can be influenced in hypnosis is beyond all manner of doubt; but the same result is often obtainable when such patients are awake.

If, however, sleep and hypnosis are to be considered identical, then the spasms of typical chorea which cease in ordinary sleep ought invariably to stop in hypnosis also, and without any form of suggestion being employed. Up to the present I have never seen this happen. If other authors have obtained other results, any objection to the identity of hypnosis and sleep fails as far as these cases are concerned, but does not in the least justify us in assuming a general identification of sleep and hypnosis.

From various sides (Bernheim, Delboeuf, Max Hirsch) it has been asserted that the hypnotic subject is not asleep, but that he believes he is asleep, that the illusion of sleep produces the increase of suggestibility. A somewhat different, and perhaps, more correct view, has been expressed by Schrenck-Notzing. He divides hypnoses into those in which there is no sleep, those in which there is an illusion of sleep, and those in which actual sleep is present.

The similarity of the means used to induce sleep and hypnosis is often insisted upon as a proof of their identity. But a distinction must be made. It is said that monotonous stimuli induce both sleep and hypnosis. Purkinje, therefore, thought that Braid's methods would produce sleep. But we should never conclude an identity of states from the identity of their causes. We should observe whether their symptoms are identical. I have seen cases in which the subjects fixed their gaze, but' did not concentrate their attention. The subsequent state was an ordinary sleep, out of which the subjects awoke when I made verbal suggestions to them, however softly I spoke. It is the same thing when we wish to decide whether a tedious speaker hypnotizes his audience. Many people grow sleepy or even fall asleep, in such a case. I consider the state one of ordinary sleep produced by the subject failing to concentrate his attention. If he concentrates his thoughts on the speaker, he will not go to sleep; in this case his state of partially strained attention much resembles hypnotism. If the state is strongly marked, negative hallucinations may arise, for instance, with regard to noises, as in hypnosis.

In many works on oratory, even in Cicero's, this effect of a fine speech is referred to.

Similarly, those states of loss or disturbance of consciousness, induced by vertigo - e.g., by spinning round quickly, should not be reckoned as hypnoses. Erdmann has identified the states induced by vertigo and by tedium in his well-known ingenious manner.

Once more I must repeat my own view: it does not matter how the states are produced; the point is whether their symptoms are alike.

Hypnosis has often been compared to mental disorder as well as to sleep. Rieger and Semal, as well as Hack Tuke (so far back as 1865), called hypnosis an artificially induced mental disorder of short duration. In the first place I would remark that it is of no consequence what hypnosis is called; a name goes for nothing. Even in therapeutics this is a matter of no moment; otherwise we should have to refrain from using . morphia because it is a poison, and because the sleep induced by morphia is an effect of poisoning. Freud is right when he says that meat does not lose its flavour when a rabid vegetarian calls it carrion; why should a mental influence, such as we have found hypnosis to be, lose its value or interest because it is sometimes called a mental disease ? A remark of Griesinger shows how capriciously all such terms are used; he thinks a somnambulia of short duration is a sleep, and a longer one a mental disorder.