The book includes the main work of the famous French physiologist P. Regnard, which analyzes in detail various forms of mental epidemics that took place from the 15th to the 19th centuries. The author describes the phenomena under study and proves the existence of a connection between the historical era and the form that this or that epidemic takes - witchcraft, morphinism or delusions of grandeur. For psychologists, philosophers, cultural scientists, religious scholars and everyone interested in the problems of social psychology.