Solitary confinement is by many regarded as a mode of torture too cruel and unnatural for civilized countries to adopt. To one long pent up on a desert island the sight of a human footprint or a human form in the distance would be the most tumultuously exciting of experiences.”[3] But the impulse is also apparent in more normal experiences. So much do men desire the company of others that it is not only an element of recreation usually, but the more serious tasks of life often derive their value not more because of the ostensible end sought after than because of the human association which is involved. Wilfred Trotter[4] has made gregariousness central in his study of society. He begins by approving of the method of those who have come at the study from the standpoint of the instincts, but expresses dissatisfaction with the limits of their results, that is, dissatisfaction with the kind of analysis that would explain man by referring the whole of his conduct to the instincts of self-preservation, nutrition, and sex. Such an explanation, he finds, has been historically attempted, but after it has gone as far as it could, there has always been left over an unexplained X. Trotter accepts self-preservation, nutrition, and sex as fundamental instincts, but completes the list by bringing forward the instinct of the herd which he offers as the explanation of all human activity which was left unexplained by the other three instincts mentioned above. To Trotter there have been two great epoch-making forward steps in the evolution of life. The first came with the change from unicellular to multicellular organisms, the great advantage of which was to make the _group_ of cells the unit of selection, thus to some extent relieving the single cell of the burden of the struggle for existence, and permitting it a greater chance for variability without running a greater risk of extinction. This arrangement, says Trotter, had important influences upon all the cells comprised in the organism. The second great evolutionary advance came with the change from solitary to gregarious animals, and was attended by modifications just as profound as had accompanied the advance from unicellular to multicellular organisms. Here again the power of natural evolution operated upon the group as a unit, thus permitting once more greater variability on the part of the individual. Association in the herd became increasingly valuable in the struggle for existence, and tended to become more and more strongly fixed as a disposition of animal nature, a fact which had fundamental influence upon the mental characteristics of the individual. There are psychological traits which would not exist but for the fact of gregariousness. Shyness, embarrassment, fear, anger, love, sympathy, sorrow, and gratitude would be devoid of meaning apart from their connection with social relations.