The precise degree to which these agents have altered the intellectual and moral powers of communities has long been the theme of controversies.
This is especially true of alcohol. Professor Lapouge, certainly an unbiassed observer, citizen of a land where temperance societies are unknown, does not hesitate to call it “the most formidable agent of degeneration in modern society.” Its worst effects are not the violence to which it occasionally leads or the frightful nervous diseases which its excessive use entails, but the slow hardening of the “axis cylinders” in the nerve sheaths, the immediate consequence of which is permanent deterioration of mental activity. Extended throughout a community, this means a lessening of its energy and of its finest mental qualities. Chronic alcoholism of this kind does not materially shorten life, but it is eminently transmissible, and this soddens the stock. The white race is most exposed to these mental and nervous effects of alcohol, while the red and black races escape them in large measure.
The second class of toxic agents affecting the community at large includes the various forms of disease-germs. No one can doubt the debilitating influence of malaria on the mental faculties of the population exposed to its poisonous action. Vast tracts of the earth’s surface are by it rendered incapable of sustaining the highest types of humanity. Their energy is sapped, their vitality lowered, by the insidious miasm. No race or nationality is immune. Though the white race is most liable to its attacks, the African blacks are so far from being exempt that in the more intense malarial districts of their continent nearly one-third of the natives suffer from the disease.
Marsh poison is usually confined to the lowlands. But the mountain valleys also generate a noxious agent, most unfriendly to mental growth. It displays itself in a threefold form, embracing goitre, cretinism, and deaf-mutism, the three closely related and bringing with them a positive debility of psychical powers. The mountains have not only been the refuge of the feeble, escaping from the plains, but they have worked to render these outcasts feebler still by reducing them in stature and viability. Goitre is not confined to Alpine regions, though more prevalent there. It is distinctly hereditary, and the offspring of goitrous parents are predisposed to cretinism and allied forms of imbecility. The southern and western slopes of the Alps, the Pyrenees, the Himalayas, and the Cordilleras are especially the homes of this class of diseases.