{222} The effect of imitation in the production of hysteria has been known in all ages. Most of the epidemics and endemics of nervous disorders which have from time to time prevailed in various parts of the world have either been hysterical in character or have had in them a large element of hysteria. While it is impossible in a practical work to devote much space to this branch of the subject, a discussion of hysteria in its etiological relations would be imperfect without some reference to these outbreaks. In ancient times, in the Middle Ages, and within comparatively recent periods extraordinary epidemics have occurred. No country within the range of medical observation has been entirely free from them. Communities civilized and semi-civilized, Christian and Mohammedan, Protestant and Catholic, have had a fair share of the visitations. Some of them constitute epochs in history, and, as Hecker,[49] their greatest historian, has remarked, their study affords a deep insight into the work of the human mind in certain states of society. “They are,” he says, “a portion of history, and will never return in the way in which they are recorded; but they expose a vulnerable part of man—the instinct of imitation—and are therefore very nearly connected with human life in the aggregate.” [Footnote 49: _The Epidemics of the Middle Ages_, from the German of J. F. C. Hecker, M.D., Professor at the Frederick William University at Berlin, etc., translated by B. G. Babington, M.D., F. R. S., etc.; 3d ed., London, 1859.] Some authors under hysteria, others under catalepsy, others under ecstasy, still others under chorea, have discussed these epidemics—a fact which serves to emphasize the truth that while these affections have points of difference, they have also an easily-traced bond of union. They are but variations of the same discordant tune. Briquet in an admirable manner sketches their history from the age of Pausanias and Plutarch to the time of Mesmer. Of American writers, James J. Levick[50] of Philadelphia has furnished one of the most valuable contributions to this subject. [Footnote 50: “An Historical Sketch of the Dance of St. Vitus, with Notices of some Kindred Disorders,” _Med. and Surg. Reporter_, vol. vii., Dec. 21 and 28, 1861, p. 276, and Jan. 4 and 11, 1862, p. 322.] In the year 1237 a hundred children or more were suddenly seized with the dancing mania at Erfurt; another outbreak occurred at Utrecht in 1278.