Delbceuf draws attention to one method of making the memory last: he thinks that subjects remember any hypnotic event if they are awakened in the middle of it; but this is certainly not universally true (Gurney). On the other hand, it often happens that the first or last occurrences are remembered, while all the others are forgotten. It has often been observed that memory after awakening can be produced by a special effort of the hypnotist (Bleuler, Pierre Janet). Bernheim even thinks that memory can be produced in all cases by means of a strong suggestion after awakening, especially if the suggestion be strengthened by causing the subject to place his hand on the experimenter's forehead. Some persons remember all the hypnotic proceedings during their nightly sleep; it is not rare for the hypnotic dream to be repeated in natural sleep. It is also possible in all cases to prevent post-hypnotic amnesia by suggesting during the hypnosis that the patient on awaking is to remember all that has happened; on the other hand, post-hypnotic amnesia can sometimes be produced by suggesting to the hypnotic that he must forget all that has happened during the hypnosis. But such cases are comparatively speaking rare.

Bernheim observed cases in which, without any suggestion being made, the subject on awaking had forgotten not only what had happened during the hypnosis, but events which had immediately preceded its onset.

But if we avoid using any kind of suggestion, then, in some cases, chiefly in the deepest hypnosis, memory of even the hypnotic proceedings cannot be recalled after awakening. In such cases the person does not generally know how long he was in the hypnotic state. On the other hand, the subject remembers in hypnosis all that has happened in previous hypnoses. Things that happened in hypnoses many years back, even as many as ten, may be recalled, although they are completely forgotten in the waking state. Wolfart relates the case of a woman who remembered in the magnetic sleep all that had taken place in a magnetic sleep thirteen years before, although in the meantime she had never recollected it.

Events of the normal life can also be remembered in hypnosis, even when they have apparently been long forgotten. This increased power of memory is called hypermnesia. Benedikt relates a case of it. An English officer in Africa was hypnotized by Hansen, and suddenly began to speak a strange language. This turned out to be Welsh, which he had learned as a child, but had forgotten. Breuer and Freud point out that many cases of hysteria are called forth by some psychic moment that the patient cannot recall in the waking condition, though hypnosis may again bring it back to memory. Vogt and Brodmann have given reasons for employing hypnotic hypermnesia in therapeutics, and the former has also used it in psychological analysis. Hirschlaff, however, who has made many investigations on the subject, feels compelled to deny the existence of any increased power of recollection in hypnosis. He is convinced that the apparent increase of recollection depends either upon the suspension of an emotional form of inhibition which existed in waking-life - for example, a hypnotic will relate something which modesty would compel him to withhold in waking-life - or upon auto-suggestion brought about by the verbal suggestions of the experimenter.

Such cases of increased recollection recall others which are mentioned in the literature of hypnotism; for example, the famous one of the servant-girl who suddenly spoke Hebrew. She also, in an abnormal state of consciousness, spoke a language which she did not know, but which she had often heard when young in the house of a clergyman. We hear of like cases of hypermnesia in dreams. Maury, whose investigations on the subject of dreams are classic, relates a number of things which returned to him in dreams, although when awake he knew nothing about them. The heightened faculties of hypnotic subjects of which we so often hear, and which we can observe in auto-hypnosis also, are a result of this increased power of reproducing ideas. Many apparently supernatural facts can be explained in this way. I shall refer to this later on.

Dreams, also, which have occurred in natural sleep are sometimes reproduced in hypnosis, although they may have been forgotten on waking. It is naturally very difficult to judge of the accuracy with which dreams are reported. But as dreams sometimes leads to talking in sleep, it is then possible to make observations. I know of many cases in which persons betrayed their dreams by talking in their sleep; in several instances I was able to show that the loss of memory which followed on waking disappeared in hypnosis, and the dream was remembered. In one case a bed-fellow was able to confirm the accuracy of the recollection. The occurrences of a pathological condition may be reproduced in hypnosis just as we have seen those of a dream. Bramwell mentions a case reported by Morton Prince, in which a hypnotized person remembered many things - especially those which had occurred during the delirium of fever - which could not be recollected when the subject was in a normal state. In recent years this question has occupied the attention of several authors, among whom may be mentioned Naef, Grater, Hilger, Muralt, Heilbronner, Binswanger, and, more especially, Riklin. They endeavoured to restore in hypnosis, memory, the loss of which had been caused by epilepsy or hysteria.

Binswanger and Heilbronner consider that the amnesia of hysteria can be dispelled in hypnosis, but not that caused by epilepsy; on the other hand, Riklin concludes from his experiments that the amnesia of epilepsy may also disappear. Bramwell experimented for the purpose of ascertaining if in hypnosis a person could recollect what had happened to him when under the influence of ether or laughing gas, but only obtained negative results. Other experiments in which attempts were made to cause subjects to recollect what had gone on around them while they were in natural sleep were equally unsuccessful. A sentence was read to X. while he was asleep and repeated several times, but he was unable to recollect it when he was hypnotized. Brodmann tells us that Vogt was able to restore in hypnosis the memory in some other cases of amnesia; for example, in the acute delirium arising from neurasthenia, in post-epileptic amnesia, and loss of memory arising from some infective disease; but never in the case of a real epileptic fit.