Again, take the well-known case of the Berlin bookseller, Nicolai, who, having fallen into ill-health, for a whole year saw, when awake, visions so real and palpable that he may be said to have lived in the company of disembodied spirits, undistinguishable from actual men and women. This is a common phenomenon in vivid dreams, but the Berlin case takes us a step farther, and shows us how subjective impressions may assume the form of objective realities, even in the case of a man wide awake, of a sceptical turn of mind, and in full possession of his reasoning faculties. Why then should we be driven to the alternative of miracle or imposture, to account for similar dreams or visions being taken for objective realities by enthusiastic minds, living in an atmosphere of religious excitement, in an uncritical age, when supernatural occurrences were considered to be matters of course? And history is full of instances which show how any supernatural germ, planted in such a medium, propagates itself and extends to millions, almost as rapidly as the bacillus germ does in an epidemic of small-pox. St. Vitus’s dance, or the dancing mania, ran the round of Europe like the potato disease, and even yet survives in the hysterical affections of the sect of Shakers. The gift of tongues spread like wildfire through Irving’s congregation, and only died out because it had fallen on the uncongenial soil of the nineteenth century; even the story of the tail of the lion over the gateway of the old Northumberland House being seen by many passers-by to wag because one had asserted it, illustrates the contagiousness of nervous sympathy, and the tricks which ‘strong imagination’ can play with the senses.