political institutions, etc., in order to ascertain the causes that determine the distribution.
But the distribution of population is only partially explained by natural causes. With the same physical environment, the American people are differently distributed from the native Indians. The latter lived in tribes and congregated only in villages, because means of communication were too undeveloped and the population too small to permit the division of labor between city and country. Primitive peoples probably did not live in scattered dwellings, for man is a social being; at the present time, at least, the lowest races like the Australians and Terra del Fuegians dwell in small family groups. The group can never be very large as long as it derives its sustenance from the land it occupies. With the growth of transport facilities and the development of trade, the community may obtain its food-supply from outside sources in exchange for its own products. Then arises a differentiation of dwelling-centres and their functions, which increases pari passu with the development of methods of communication, and very noticeably affects the customs and modes of life of the inhabitants. That the townsman is different from the countryman has long been recognized in politics, law and social science. The names "pagan" and "heathen" originally designated countrymen, while the abjective "urbane" and the nouns "citizen" and "politics" are derived from the Latin and Greek terms for city. In modern German "kleinstädtisch" is a term of reproach, while in nearly all languages there exists a strong antithesis between "citified" and "countrified."
As our study proceeds, we shall discover fundamental differences in the structure of city and rural populations, which underlie and explain the ordinary manifestations of disagreement just noted. But the first step must be the determination of a method of measurement that can be used with some