For these reasons the study of causes in ethnic pathology becomes of enormous practical moment. Only by an acquaintance with them can preventive and curative remedies be applied. These causes are, at first, always _external_ and _individual_. They proceed from some form of “environment,” mental or physical. But the morbid impression, once fully received, is often indelible, becomes fixed in the type, and is but little influenced by external agencies. These primary causes of true ethnic degeneration I shall consider under four headings. 1. Imperfect Nutrition. 2. Sexual Subversions. 3. Toxic Agents. 4. Mental Shocks. No one of these can act in the long run in other than a deleterious manner on the ethnic mind. There is nothing “compensatory” in any one of them or so little that it need not be reckoned. 1. _Imperfect Nutrition._—It has been said broadly that all psychopathic and regressive conditions arise from malnutrition (Féré). This is true, in a sense, but does not carry us far in the direction of treatment. We ask a closer definition of origins. There is no doubt of the intimate relationship of ample nutrition and intellectual progress; but while it is well to avoid the ancient notion of the independence of soul and body and that the former is superior to the latter, we must guard against the modern extreme of Buckle and his followers, that the history of nations can be traced to the food they eat. Man is omnivorous, and his well-being is nourished by food of any kind, providing it is nutritious and easily assimilable. The effort which has often been made to trace the character of tribes and nations to some prevalent diet—be it of fish or flesh, or vegetable products—is fanciful, and yields no positive facts. What does harm is not some particular kind but a general insufficiency of aliment. Imperfect nutrition may be traced to three principal sources. 1. Insufficient or unsuitable food. 2. Lack of variety. 3. Improper preparation of food. The careful researches of Collignon, Ranke, Ammon, and others have traced the stunted forms, defective bodies, and low intellectual development of the Lapps, the mountaineers of central Europe and the Bushmen of the Kalihari desert to one cause, _la misére_, lack of sufficient and appropriate food. This is certain to bring about degeneration of organs, incomplete development, and loss of brain power. Continued through generations, a hereditary taint is engendered which saps the vigour of the stock, and cannot be eradicated by improved conditions. Unsuitable food is usually consumed on account of the scarcity of better material, but at times from a morbid craving. Examples are the unctuous clay which was swallowed by various tribes in America and Australia, and also by some of the “poor white trash” of Georgia. The ergoted rye and maize to which some of the peasantry of France and Italy are forced to have recourse exerts a disastrous influence on both body and mind.