Equally significant in the history of religion is the dancing mania, which broke out as the mania for flagellation was subsiding. The function of dancing in primitive religious ceremonial has been pointed out in a previous chapter. It is there a common and obvious method of both creating and expressing a high state of nervous excitability. In later times religious dancing becomes more purely hypnotic in character, and suggestion plays a powerful part. During the medieval period the conditions were peculiarly favourable to the prevalence of psychological epidemics. Plagues, more or less severe, were of frequent occurrence. Between 1119 and 1340, Italy alone had no less than sixteen such visitations. Smallpox and leprosy were also common. The public mind was morbidly sensitive to signs and portents and saturated to an almost incredible degree with superstition. The public processions of the Church, its penances, and practices were all calculated to fire the imagination, and produce a mixed and dangerous condition of fear and expectancy. Moreover, dancing mania, on a small scale, had made its appearance on several previous occasions, and the public mind was thus in a way prepared for a more serious outbreak. The great dancing mania of 1374 occurred immediately after the revels connected with the semi-Pagan festival of St. John. Bacchanalian dances formed one of the accompaniments of the festival of St. John, and made, so to speak, a natural starting-point for the epidemic. Hecker, who gives a very elaborate account of the dancing mania as it appeared in various countries, thus describes the behaviour of those afflicted:-- "They formed circles, hand in hand, and, appearing to have lost control over their senses, continued dancing, regardless of all bystanders, for hours together, in wild delirium, until at length they fell to the ground in a state of exhaustion.... While dancing, they neither saw nor heard, being insensible to external impressions, but were haunted by visions, their fancies conjuring up spirits whose names they shrieked out; and some of them afterwards asserted that they felt as if they had been immersed in a stream of blood, which obliged them to leap so high. Others, during the paroxysm, saw the heavens open and the Saviour enthroned with the Virgin Mary."[184] At Aix-la-Chapelle, Cologne, and Metz, says the same writer:--