It is doubtful whether such experiments would succeed with persons who had never heard of hypnotism. Schrenck-Notzing reports a case in which hypnosis was produced from post-epileptic coma. Cases in which conditions of hysterical sleep have been led on into hypnosis have been described by Lcewenfeld and others. I may refer here to the question already raised, whether hypnotic states can be produced by chemical substances, such as chloroform, etc.

In any case, however, previous consent is not absolutely necessary to the production of hypnosis, and, on the other hand, there are people who are refractory in spite of a decided wish to be hypnotized. In general, however, the intentional resistance of the subject hinders hypnosis, because a person who is willing to be hypnotized complies more easily with the necessary conditions than another. Consequently, it is not astonishing that patients who come to a doctor on purpose to be hypnotized, particularly when they come with full confidence, are more easy to hypnotize than others. These others often allow an attempt to be made with them, with the silent resolution that "they are not to be caught," or they submit themselves, as Nonne says, "only for fun."

As so many different circumstances influence the induction of hypnosis, it is not surprising that the proportion of hyp-notizable persons should be differently stated. If Ewald in the Women's Hospital at Berlin can only hypnotize two persons, while Liebeault hypnotizes 92 per cent. of his patients, the reason of this enormous difference must lie in the disparity of the conditions. The insufficient mental preparation of Ewald's subjects is particularly to blame for his failure. Bottey gives 30 per cent, as susceptible, Otto Binswanger more than 50 per cent, Morselli 70 per cent., and Delbceuf more than 80 per cent. The latter's data appear to me of great value, having been evidently collected with critical care. As he excludes simulators, he appears to me more sceptical than the investigators at Nancy. The highest percentage of successes was obtained by Vogt, who states he did not find one thoroughly refractory case in 119 subjects experimented on by him. Bramwell makes a similar statement with regard to a particular section of his patients, Bernheim refuses the right to judge of hypnotism to all hospital doctors who cannot hypnotize at least 80 per cent, of their patients.

Forel fully agrees with him.

An international investigation on aptitude for hypnosis has been made by Schrenck-Notzing, who applied to numerous investigators in various countries - England, Sweden, Germany, France, Algiers, Canada, and Switzerland. Among 8,705 persons covered by the investigation, only 6 per cent. were completely refractory. The remaining 94 per cent, were divided by Schrenck-Notzing into three groups, according to Forel's classification, of which I shall soon have to speak: 29 per cent, attained to somnolence, 49 per cent. to hypotaxis, 15 per cent. to somnambulism.

The oftener hypnotic experiments are made the sooner is hypnosis generally induced. The first attempt often takes five minutes or more, although on many occasions a few seconds suffice. When the experiment has succeeded a few times, a few moments are nearly always enough to attain the result. This is because the remembrance of the earlier hypnosis essentially favours its return. Besides this, the strongest hindrance has been overcome by the earlier hypnosis - which is the belief of the subject that he is not hypnotizable, a belief which often prevents hypnosis. The certainty with which well-known hypnotizers hypnotize people, rests partly on the fact that these subjects believe that some hypnotizers possess a greater aptitude for hypnotizing them than others do. On the other hand, Rosenbach and Eschle go too far in their contention that "the nimbus of the hypnotizer" is the essential factor in producing hypnosis. "It is to the mysticism of the subject to be hypnotized, in the form of a naive but firm belief, and not to that of the hypnotizer, that we must look for an explanation of the fact that the former person submits to the influence of the latter." This is Eschle's opinion, but auto-hypnosis forbids an all-round acceptance of this view.

Although we have seen that the disposition to hypnosis increases the oftener experiments are made, it may also disappear when the experiments have been discontinued for a long time. But the disposition to hypnosis can generally be reproduced if a few attempts are made. Still, I have seen cases in which subjects who were at one time easily hypnotized later on become altogether refractory, and for no apparent reason. •

From the above examples it appears that the various hypnotic states differ much from one another, especially where the depth of the hypnosis is concerned. This suggested that in order to obtain a general survey an attempt at classification must be made.