Human beings are, however, not merely organisms: they are the home and the habitat of minuter organisms. The human body is, in a certain sense, an organization--a sort of social organization--of the minute and simple organisms of which it is composed, namely, the cells, each of which has its own characteristic mode of behavior. In fact, the life of human beings, just as the life of all other creatures above the simple unicellular organisms, may be said to consist of the corporate life of the smaller organisms of which it is composed. In human beings, as in some great city, the division of labor among the minuter organisms has been carried further, the interdependence of the individual parts is more complete, and the corporate life of the whole more complex. It is not strange, therefore, that Lloyd Morgan begins his studies of animal behavior by a description of the behavior of the cells and Thorndike in his volume, _The Original Nature of Man_, is led to the conclusion that the original tendencies of man have their basis in the neurones, or nerve cells, and in the changes which these cells and their ancestors have undergone, as a result of the necessity of carrying on common and corporate existences as integral parts of the human organism. All acquired characteristics of men, everything that they learn, is due to mutual stimulations and associations of the neurones, just as sociologists are now disposed to explain civilization and progress as phenomena due to the interaction and association of human beings, rather than to any fundamental changes in human nature itself. In other words, the difference between a savage and a civilized man is not due to any fundamental differences in their brain cells but to the connections and mutual stimulations which are established by experience and education between those cells. In the savage those possibilities are not absent but latent. In the same way the difference between the civilization of Central Africa and that of Western Europe is due, not to the difference in native abilities of the individuals and the peoples who have created them, but rather to the form which the association and interaction between those individuals and groups of individuals has taken. We sometimes attribute the difference in culture which we meet among races to the climate and physical conditions generally, but, in the long run, the difference is determined by the way in which climate and physical condition determine the contacts and communications of individuals.