(b) _Psychical._--From the psychical side, he explained the phenomena of hypnosis by the action of predominant and unchecked ideas. These were able to obtain prominence from the fact that other ideas, which, under ordinary circumstances, would have controlled their development, did not arise, because the portion of the brain with which the latter were associated had its action temporarily suspended--_i.e._, the connection between the ganglion-cells was broken, owing to the interrupted connection between the "fibres of association." Thus, he said, the remembrance of a sensation could always be called up by the brain; but, under ordinary circumstances, from the exercise of judgment, comparison, and other mental faculties, we knew it was only a remembrance. When these faculties were exhausted, the suggested idea predominated, and the individual believed in its reality. Thus, he attributed to the faculties of the mind a certain power of correcting the fallacies which each of them was likely to fall into; just as the illusions of one sense were capable of being detected by the healthy use of the other senses. There were mental and sensorial illusions, the former caused by predominant ideas and corrected by proper reasoning, the latter caused by perversion of one sense and corrected by the right application of the others. In hypnosis, according to this theory, a suggested idea obtained prominence and caused mental and sensorial illusions, because the check action--the inhibitory power--of certain higher centres had been temporarily suspended. These theories were first published by Professor Bennett in 1851. _III.--Hypnotic Induction_ The methods by which hypnosis is induced have been classed as follows: (1) physical; (2) psychical; (3) those of the magnetisers. The modern operator, whatever his theories may be, borrows his technique from Mesmer and Liebeault with equal impartiality, and thus renders classification impossible. The members of the Nancy school, while asserting that everything is due to suggestion, do not hesitate to use physical means, and, if these fail, Bernheim has recourse to narcotics.