INTRODUCTION TO SOCIOLOGY 243
better to the more and more special external necessities ; and in accommodating themselves they even modify the earth to their advantage. This superior power of adaptation of the human species involves at once its greater relative fixity and superior idaptation in temporarily or permanently displacing itself. Thus the highest civilizations are at the same time the most sedentary and the most mobile more mobile, in fact, in that which con- cerns their constituent units than primitive societies, which are especially altogether sedentary or altogether nomadic ; but even when nomadic they are sedentary in the sense that they transfer themselves only into simple and analogous regions. The advanced civilization enjoys in the highest degree a mobile equilibrium through an apparent reaction, which is, in fact, a superior combination of the double power of fixation and displace- ment. It is sometimes in the laws of the ordinary animal life that we discover the foundation of the most complex laws of the distribution of the human species, from its origin up to the most advanced stages. In them we also comprehend that the structure and life of societies, through the intermediation of the flora and fauna, are connected with the great laws of universal mechanics. That which is especially important to remember, from the point of view of the mammifers, is that each species has, it is true, its area of habitation, more or less determined by geography, climate, and the mode and quantity of elimination in relation to its peculiar structure, but that, aside from the great climatic mutations of which we have spoken, some of the habitats of the mammifers are relatively fixed. In others, although there are sundry zoological regions, these regions, as natural history shows, are bound together by some common characters. This com- munity and this fundamental zoological solidarity join with the unity and solidarity of the physical world, recognized by us previously up to the orographical and hydrographical structure which produces the most impassable obstacles and natural divisions.
We are now prepared to examine the same problems with .respect to the human species a species which is becoming more
