Concentration of populations in cities, the wider markets, the division of labor, the concentration of individuals and groups on special tasks, have continually changed the material conditions of life, and in doing this have made readjustments to novel conditions increasingly necessary. Out of this necessity there have grown up a number of special organizations which exist for the special purpose of facilitating these readjustments. The market which brought the modern city into existence is one of these devices. More interesting, however, are the exchanges, particularly the stock exchange and the board of trade, where prices are constantly being made in response to changes, or rather the reports of changes, in economic conditions all over the world. These reports, so far as they are calculated to cause readjustments, have the character of what we call news. It is the existence of a critical situation which converts what were otherwise mere information into news. Where there is an issue at stake, where, in short, there is crisis, there information which might affect the outcome one way or another becomes “live matter,” as the newspaper men say. Live matter is news; dead matter is mere information. What is the relation of mobility to suggestion, imitation, etc.? What are the practical devices by which suggestibility and mobility are increased in a community or in an individual? Are there pathological conditions in communities corresponding to hysteria in individuals? If so, how are they produced and how controlled? To what extent is fashion an indication of mobility? What is the difference in the manner in which fashions and customs are transmitted? What is social unrest, and what are the conditions under which it manifests itself? What are the characteristics of a progressive, what the characteristics of a static, community in respect to its resistance to novel suggestions? What mental characteristics of the gypsy, of the hobo, and of the nomad generally can be traced to these nomadic habits? _The stock exchanges and the mob._—The exchanges, upon which we may watch the fluctuation of prices in response to the news of economic conditions in different parts of the world, are typical. Similar readjustments are taking place in every department of social life, where, however, the devices for making these readjustments are not so complete and perfect. For example, the professional and trade papers, which keep the professions and the trades informed in regard to new methods, experiences, and devices, serve to keep the members of these trades and professions abreast of the times, which means that they facilitate readjustments to changing conditions.