In the interest of the quantification of the population geography, it is necessary to pay attention not only to the delimitation of units but also to their internal character. In the first part of the article the author treast of the substance of a population unit. The concentration of population into smaller or larger geographical wholes has taken place since primeval ages for economic purposes, and since its very beginning it was contingent on a definite integration power; as a prototype may serve the function of a clan chief or the mayor in a municipality. Occupational differenciation occurred due to the technical development, and regional differences increased in this way, too. Economic and social differences inside the unit, and between individual units caused the shifting of population which is irreversible, tending to the tertiary sector. These conditions are represented at a graphical chart (Fig. 1.). The area of the oblong represents the frequency prisms of sector I, II, and III whose base is the area, and height the number of inhabitants in those sectors. The vertical axis of the chart represents the integration factor. Arrows mark the direction of the general shifting of population. If the shifting inside a unit is everywhere of the same character and is directed to the same destination, i. e. to sector III, and if the shifting between the units is of the same character and is directed to a unit of a higher order, then the quantitative proportion between the numbers of inhabitants of the biggest town and the population of its economic hinterland should equal in all places. Such conditions are mentioned by W. Christaller as prevailing in South Germany. In the second part the author tries to verify any periodicity of this kind in Europe at least for the units of the highest order, i. e. for Landstädte, according to Christeller. For these 37 towns the author compiled the following statistical data: a) extent of the economic hinterland in 1000 km2 b) average density of population on 1 km2 in 1000 c) number of inhabitants in largest agglomerations (C) in 1000 d) number of inhabitants in other economic hinterlands (A) e) ratio C:A in percent. The ratio C:A remains in 30 areas with capitals having 1000 up to 2500 inhabitants, approximately the same, the average deviation being 20 % from the total average. Greater periodicity cannot be expected since even the shape of natural crystals never corresponds exactly to crystallographic rules. The statistic correlation between the density of population and the ratio C:A is plotted into a graph in Fig. 2. The values of this coefficient are on the whole parallel with the axis x (abstracted from external values exceeding 100 %), which indicates the maximum dependence upon the density of population. It is also interesting that the ratio lies almost in the middle of the variation series. The above mentioned Christaller rule is effective for European centres of the highest order. It is impossible to carry out an analogical analysis for centres of lower order beacuse of the lack of sufficiently detailed data. It may be expected, however, that the periodicity will be the greater, the higher is the order of the biggest town in the area under investigation.