Another evidence of exhaustion, one which properly exercises the attention of the student of modern life, is the progressive distaste for the sex relation, especially among women. The consequences of this mental attitude are the prevalence of spinsterhood and the limitation of families in marriage, to which I have already referred. The attraction of the “higher culture” and of their new facilities for seeing and enjoying liberty have led to atrophy of the maternal instinct and of the desire of marriage. This can have but one result,—the diminution and final extinction of the group in which it prevails. There is also such an ethnic malady as moral exhaustion. After a period of intense but ill-regulated ethical enthusiasm there often follows a reaction, when all ethical principles are thrown to the winds. This has been plausibly explained by Dr. Laycock as an overstimulation of the brain-cells most closely connected with this class of sentiments, with consequent exhaustion in transmission to the next generation. “The fathers have eaten sour grapes and the children’s teeth are set on edge.” The bigotry of Puritan England in the 17th century was followed by the laxity of the Restoration. PART II THE NATURAL HISTORY OF THE ETHNIC MIND _INTRODUCTION_ Although, as we have seen, there is no common measure of Mind and Matter, the connections between the two are so intimate that, in organised beings, any change in the one entails a corresponding change in the other. This is a principle which has long been accepted in the Science of Man. A quarter of a century ago Professor Schaffhausen expressed it in these words: “One of the weightiest doctrines in Anthropology is the constant correlation between intellectual capacity and physical organisation.” That branch of Anthropology called Somatology is devoted to the investigation of the human body, its measurements, structure, and functions, as they differ in individuals, groups, and races, for the purpose of defining and explaining this correlation. The expressions of the individual mind are largely the reflex of its environment, of the external impulses, stimuli, and conditions which surround it. These are physical, measurable, quantitative, and therefore within the province of the “natural” sciences. In their relation to the individual, they mostly belong to the domain of “experimental” psychology; but as they influence the group and decide its constitution they form an important branch of ethnic psychology also. The natural history of the Mind is chiefly the study of its environments, its _milieu_. But that term is to be taken in its widest sense. The nearest environment of my mind is my body. Indeed, it is the only environment of which I have positive knowledge. As John Stuart Mill well said, “I know my own feelings with a higher certainty than I know aught else.”