INTRODUCTION TO SOCIOLOGY 399
organisms which attain to, but do not go beyond, a certain struc- tural development incompatible with their immortality. 1
When the organized mass which formerly produced the phenomena of life produces them no longer and will never again produce them, it is death. .... The duration of life is exactly adapted to the conditions of life. It is lengthened or shortened, in the course of a formation of a species, according to the conditions of life of the species. In a word, it appears absolutely as an adaptation to the conditions of existence.
Life is therefore an equilibrium of the organism at once internal and external, an equilibrium at once stable and mobile.
But societies are the rashest, most complex, and most plastic organisms, and they are the most capable of continued adapta- tions. The result is that their structure, their extent in space, and their duration in time may be alike more extended and more durable by means of adapting themselves more and more in space and time to the conditions of social life. Societies are naturally neither mortal nor immortal, but they may extend and prolong their growth within limits less narrow than any other organism excepting the unicellular organisms. Theoretically they can accomplish the same result through their complexity that the unicellular organisms accomplish through their simplicity.
Hence in the individual organisms the limits of structure and life are determined by the conditions of life. The latter, through adaptation and natural selection, fix the aptitudes of the germ, and afterward of the structure and life which are transmitted and conserved through heredity. The germ of organisms is there- fore not the absolute beginning of them. It is the product of a relation, of continued natural selection, fixed and transmitted through heredity, of an adaptative, that is to say, of a constant static equilibrium in its mobility, which necessarily implies two terms, a subject and an object, the one capable and the other susceptible of adaptation.
We see, then, in the last analysis where the study, from the very first so obscure and complex, has led us, concerning the relations of the external environment to the human species, from the standpoint of the natural distribution of this latter over the
1 La -vie et la mart.
