Men have a gregarious instinct which, under the influence of excitement, induces them to herd together without any definite object and often at great inconvenience to themselves; the progress of the resulting congestion is normal until a certain point is reached, the point at which entirely new forces begin to act. When this moment arrives, all self-control is repudiated, decent and orderly men become desperadoes, cowards are inspired by a senseless bravado, the calm reason of common-sense gives place to the insanity of licence, and unless the demoralising tendency is checked, a crowd rapidly reaches the level of its most degraded constituent. The explanation of these phenomena is probably to be found in an excessive spirit of emulation aroused under conditions of excitement, which makes a man feel that the responsibility for his actions is no longer to be borne by himself, but will be shared by the multitude in which he has merged his identity. It is the business of the police to exhaust every art in a sustained effort to prevent the ferment from reaching the critical stage, and to watch the crowd so narrowly that the first symptom of violence may instantly be suppressed. This can best be accomplished by local constables who are acquainted with the persons and names of individual members of the crowd, while it is of even greater moment that the constabulary should not be the first to give offence, or contribute to a breach of the peace by the use of exasperating language or aggressive action.