Similarly, the suggestibility of crowds throws light on many phenomena recorded in universal history and the history of civilization, no matter whether we take the Crusades or those mental epidemics known as St. Vitus's dance, dancing mania, and the flagellation mania, which at one time raged so furiously in Germany, the Netherlands, and Italy, and processes analogous to which are reported as also occurring in Abyssinia (J. F. C. Hecker); it matters not, I say, whether we are dealing with the obsessions of the Middle Ages or with epidemics of convulsions, none of these phenomena is comprehensible from the psychological point of view unless we take the suggestibility of crowds into consideration. Flechsig endorses Bechterew's statement that history, and more particularly the history of civilization, affords such striking instances of the mighty effects of suggestion that it should hardly be possible for any historian to pass them by unnoticed.

Hypnotism sometimes accomplishes a marvellous feat in providing us with an explanation of mental epidemics, as, for instance, in those cases in which whole districts have been infected with lycanthropia, or zoanthropia--i.e., their inhabitants suddenly imagined they were turned into wolves or other animals. Epidemics of zoanthropia occurred frequently in the Middle Ages, and even later. People usually believed they were changed into wolves, and they then attacked and tore others, and displayed the fierceness and instincts of wild beasts. This phenomenon was usually supposed to be the work of the devil. Herodotus and Pliny mention the occurrence of like phenomena in ancient times, and Johann Wier has given us details of later epidemics. Baret reports that in a form of insanity occurring in Japan the subject believes that he has been changed into a fox. It is popularly believed that such a person is possessed by a fox, and the condition is called Kitsune-tsuki. This at once recalls those cases in which hypnotized persons are induced by suggestion to believe that they are transformed into animals.

The foregoing considerations should show the extent to which hypnotism has enriched the most different domains of psychology. But we shall see from what follows that recognition of the psychological value of hypnosis has helped to advance other branches of research - ethnology and the history of civilization, for instance. This is solely due to the fact that the psychological character of hypnosis has become more and more recognized, but this has only taken place gradually.

I may here remind the reader that in 1880, when Heidenhain considered hypnosis a purely physical state, Rosenbach pointed out the psychological importance of hypnosis and was almost completely ignored! Heidenhain thought that the imitative movements were simple reflexes caused by the subject seeing similar movements made; catalepsy and echolalia were mere physical reflexes, and psychic influence was entirely ignored. Charcot, also, did not escape making similar mistakes. Since then, the importance of psychic influence for inducing the symptoms of hypnosis has been recognized to such an extent through the efforts of the Nancy School that the physical symptoms are probably even underrated. This change, which gradually led from the former physical to the present-day psychological conception of hypnosis, could not help having an important effect on psychology in general, since it brought with it hitherto unsuspected proofs of the importance of certain psychical processes, especially suggestion. To-day, impartial examination shows that in many places psychology contains traces of hypnotism and of the theory of suggestion.

Let the reader take a modern work - such, for example, as the Leitfaden der Psychologic of Lipps, who is one of the few independent psychologists of the present day - and he will there find evidences of hypnotic research in sections other than those specially devoted to that domain. The theory of self-projection is so intimately connected with suggestion that without the latter Lipps would have been quite unable to establish the former. We find something similar in other provinces of modern psychology (v. Ribot's works on Memory, Personality, Will, etc.). Psychology has also benefited by the fact that many persons first acquired a general interest in psychological processes through studying hypnotism. And by providing psychology with so many fresh fields of view, hypnotism has helped to prevent numerical psychology from exercising supreme power to-day in the manner the representatives of this domain of research hoped only twenty years ago.

Of course, we must also avoid exaggerating the importance of hypnotism. Some people thought they were able even to solve the chief problems in cerebral physiology by means of hypnosis, but this turned out to be erroneous. Mistaken interpretations have given rise to these errors. I may here refer to what I said about phreno-hypnotism on page 86, Nevertheless, such errors recur occasionally. Just as Berillon did formerly, so Grasset in the present day still believes that hemi-hypnosis proves that the two cerebral hemispheres act independently. This is but an instance of the kind of exaggeration met with in every domain of research (cf. p. 87). Similarly, the theory of the Double-Ego has nothing to do with any disturbance in the equilibrium of the two cerebral hemispheres, as some assume to be the case. Krauss, in his biography of Ribot, lays stress on the fact that the latter has refuted this theoretical deduction. There are individuals who think they possess a triple personality; thus, a priest got himself so involved in the mystery of the Trinity that, he believed himself to be three distinct persons, and wanted three places laid for him at table.

Here we see the above-mentioned physiological interpretation of hypo-consciousness carried at once ad absurdum.

Hypnotism has, nevertheless, had its influence on physiology, if only more in a negative way, in that physiological explanations have had to give way to psychological ones. At the same time, it must certainly be admitted that psychical influences are ultimately physiological processes, only we are to-day so far off any possible means of explaining this, that it is better to keep our conception of them untrammelled by physiology. In former times the possibility of explaining such states as sleep by means of chemical and physical theories was often exaggerated. Nevertheless, it is impossible to establish a satisfactory theory of sleep without taking psychology, and suggestion in particular, into consideration. This is not to be taken to mean that we look upon sleep itself as a phenomenon of auto-suggestion - a view to which some people incline - but that the psychological factors must invariably be considered in conjunction with the physiological; both play a part. The fact that excitement will banish the severest symptoms of fatigue instantaneously, discloses the psychological factor; and the fact that sleep becomes a necessity after a long vigil probably has a physiological explanation. It is the same with muscular fatigue.

Vignolle has recently published a work on fatigue, in which he very properly separates the subjective moment in the production of fatigue from the objective. Even if muscular fatigue is brought about by chemical and physical changes, it is, nevertheless, greatly influenced by psychical processes. The thought of soon getting tired may bring on the feeling of fatigue. It is, for example, in consequence of psychical processes that people who are thoroughly worn out by a long tramp lose the feeling of fatigue without taking the rest necessary for the elimination of the "fatigue-stuffs " - a phenomenon often observed, for instance, when the goal is nearly reached. There are many other cases in which it could be shown that the study of hypnotism has diminished the domain of physiological theories in this connection, in that it has demonstrated the importance of suggestion, and especially that of auto-suggestion.