famous financial undertakings rich enough to purchase every assistance— what is called a current of opinion is formed and the powerful mechanism of contagion intervenes. Ideas, sentiments, emotions, and beliefs possess in crowds a contagious power as intense as that of microbes. This phenomenon is very natural, since it is observed even in animals when they are together in number. Should a horse in a stable take to biting his manger the other horses in the stable will imitate him. A panic that has seized on a few sheep will soon extend to the whole flock. In the case of men collected in a crowd all emotions are very rapidly contagious, which explains the suddenness of panics. Brain disorders, like madness, are themselves contagious. The frequency of madness among doctors who are specialists for the mad is notorious. Indeed, forms of madness have recently been cited—agoraphobia, for instance—which are communicable from men to animals.
For individuals to succumb to contagion their simultaneous presence on the same spot is not indispensable. The action of contagion may be felt from a distance under the influence of events which give all minds an individual trend and the characteristics peculiar to crowds. This is especially the case when men's minds have been prepared to undergo the influence in question by those remote factors of which I have made a study above. An example in point is the revolutionary movement of 1848, which, after breaking out in Paris, spread rapidly over a great part of Europe and shook a number of thrones.