The mental methods induce hypnosis by giving a particular direction to the subject's imagination; this is done either by concentrating the attention on an arbitrary point (Braid), or by raising an image of the hypnotic state in a patient's mind. The latter is most easily done by speech, as we have seen in the fourth of the examples given above. This process deserves particular attention, as by the use of it unpleasant accompanying phenomena are more surely avoided. As a matter of course, the methods are slightly modified to suit special cases, because individual character plays an incomparably larger part in mental states than in ordinary physiological investigations. It is, of course, quite possible to call up the image of the hypnotic state, and thereby induce hypnosis by other means than speech; upon this fact depends the influence of imitation. The hypnotic state is occasionally induced by the mere sight of others in that condition, as well as by speech. The recollection of earlier hypnosis has the same effect; upon this fact depends the induction of hypnosis by means of letters or by the telephone (Liegeois).

In many instances the best results are obtained by taking the patient by surprise (Sperling, Forel, Eeden, Renterghem).

Vogt prefers a method which he terms fractional hypnosis. This consists in the rapid repetition of experiments, allowing the patient short intervals in which to relate his experiences and feelings, and thereby enabling the experimenter to modify his procedure if necessary. This method is said to have greatly increased the roll of somnambulists. Loewenfeld also has developed a particular method of his own. The person to be hypnotized is first of all requested to keep on counting from 1 to 100, slowly and gently. Loewenfeld then proceeds to verbal suggestion on the lines of the Nancy school, but, as a rule, precedes this by a brief fixation of the gaze. He does not straightway suggest the symptoms of fatigue as evinced by the eyes, but rather attempts to bring about a condition of rest and tiredness.

It is certain that these mental influences play a large part in hypnosigenesis. It is equally sure that they suffice in many cases to produce hypnosis, particularly when the person concerned has already been hypnotized. Many even consider the mental factor as indispensable to hypnosis; they hold the opinion that all the other methods mentioned below only succeed when they are of a kind to call up the picture of hypnosis. Yet the other point of view has many adherents, a fact which may easily be overlooked nowadays. Crocq, the most decided exponent of the view that every case of hypnosis is not necessarily the result of suggestion, supports this contention on the corroborative opinions of many other investigators, among whom may be mentioned Charcot, Richer, Pitres, Boirac, Sanchez Herrero, Marot, Azam, A. Voisin, Beaunis, Bremaud, Lajoie, David, and others.

Faria formerly made use of a mental method to obtain hypnosis. After he had strained the attention of the subject as much as possible he called out suddenly, "Dormez!" ("Sleep!"). Liebeault substantially developed and completed this process; Bernheim made it more universally known.

Here also belongs auto-hypnosis, or self-hypnosis. In this the idea of hypnosis is not aroused by another person (hetero-hypnosis), but the subject generates the image himself, either voluntarily or involuntarily. Just as the will is otherwise able to produce particular thoughts, so it can allow the idea of hypnosis to become so powerful that finally hypnosis is induced; this is, however, rare. Hypnosis generally takes place in consequence of some incident by means of which the idea of hypnosis is induced; this often happens when the subject has been frequently hypnotized. Certainly it is not always possible to make a sharp distinction between auto-hypnotism and hetero-hypnosis. It is possible that some states of sleep which are generally considered pathological, belong to auto-hypnosis.

I will now speak of the physical means, which for a long time were the only ones used. They consist of certain stimuli of sight, hearing, and touch. Taste and smell (Binet, Fere) have rarely been tried, and have generally given negative results.

The best known is the so-called method of Braid, in which hypnosis is caused by a fixed gaze at some object or other. It is of little consequence whether the object is bright or not (Gigot-Suard, Durand de Gros). Later, Braid gave up placing the object so close as to cause convergence. It is considered advantageous to hold the object so high that the eyelids are strained as much as possible in keeping the eyes open. Instead of a lifeless object, the experimenter can make use of his finger for the purpose, or, as the professional magnetizers prefer to do, of his eye (du Potet).

Luys proposed the use of a rapidly revolving mirror, in order to produce speedy and extreme fatigue of the eye. Lemoine, Joire, and others have pointed out that Luys's method enables us to hypnotize some hysterical and mentally afflicted patients, in whom hypnosis cannot otherwise be induced. The original apparatus designed by Luys has since been subjected to many modifications, more especially at the hands of Berillon and Pau de Saint-Martin. Berillon states in his brochure on the Psycho-Physiological Institute of Paris that he has exhibited various other instruments designed for the purpose of inducing hypnosis, such as that of Ch. Verdin; also, Aubry's magnesium lamp and Gaiffe's Casque vibrant. Bellemaniere introduced a further modification by means of which sight and hearing could be stimulated simultaneously.

Just the same effect can be produced by hearing as by sight; for this the ticking of a watch is preferred (Weinhold, Heidenhain). Among uncivilized races particular instruments are used to produce analogous states; for example, the sound of a magic drum among the Lapps; among other races the monotony of uniform rhythm in song (Bastian). Instead of these continuous, monotonous, weak stimulations of the senses, we also see sudden and violent ones made use of; for example, in the Salpetriere, the field of Charcot's work, the loud noise of a gong or a sudden ray of the Drummond light. However, it is more than doubtful whether these sudden strong physical stimuli, without any mental effort, can induce true hypnosis. Perhaps we have here to do with states in which paralysis from fright is intermixed with hypnosis; at least, subjects thus hypnotized often wear an expression of fear (Richer). The effect can also be produced through the sense of touch, even by a gentle stroking of the skin, or by pressure upon it. We know that Celsus was acquainted with this latter fact.