Conditions very favourable to mass-suggestion prevailed during the middle ages of European history; for these "dark ages" were characterized by the existence of dense populations, among whom there was free intercourse but very little positive knowl edge of nature, and who were dominated by a church wielding immense prestige. Hence the frequent and powerful operations of suggestion on a large scale. From time to time fantastic beliefs, giving rise to most extravagant behaviour, swept over large areas of Europe like virulent epidemics—epidemics of dancing, of flagel lation, of hallucination, of belief in the miraculous powers of relics or of individuals, and so forth. At the present time, modi fied instances are the popular pilgrimages to Lourdes, Holywell and other places that acquire reputations for miraculous curative powers.
external event or some bodily change, or through some interpreta tion of the behaviour of other persons; e.g., a man falls on the road and a wagon very nearly passes over his legs, perhaps grazing them merely; when he is picked up, his legs are found to be paralysed. The event has induced the conviction that his legs are seriously injured, and this conviction operates so effectively as to realize itself. Or a savage, suffering some slight indisposition, interprets the behaviour of some person in a way which leads him to the conviction that this person is compassing his death by tneans of magical practices ; accordingly he lies down in deep despond ency and, in the course of some days or weeks, dies, unless his friends succeed in buying off, or in some way counteracting, the malign influence. Or, as a more familiar and trivial instance of auto-suggestion, we may cite the case of a man who, having taken a bread pill in the belief that it contains a strong purgative or emetic, realizes the results that he expects.