In modern life, notably in France and the eastern United States, there is a very observable infecundity in certain classes, and they the wealthiest and best educated, due unquestionably to intention on the part of the married—to purely psychic causes, therefore. In the “best society” of those localities two or three children to a marriage are as many as are wanted and as many as arrive. That this limitation is deliberate, and not the result of reproductive debility, has been shown by an application of the law of sex at birth as formulated by Dumont. This is, that when the proportion of the sexes at birth are as 105 males to 100 females, the diminished natality is voluntary; and when it is involuntary, due to disease or malformations, this ratio is always disturbed. As statistics prove that in modern life two-thirds of the children born alive never perpetuate their kind, through death, the single life, sterility, or other reason, it is plain that intentional limitation of offspring to a number less than four means certain extinction of the family. 3. _Toxic Agents._—The toxic agents of ethnic degeneration belong to two classes, stimulant-narcotics and disease-germs. The former are voluntarily consumed by the individual, the latter he absorbs through exposure to insalubrious conditions. Both belong to preventable causes of deterioration. Of the stimulant-narcotics, alcohol, opium, and tobacco are the most familiar. But they by no means exhaust the list. Everywhere and at all times man has had an intense craving for these nervines. Where the Koran forbids alcoholic drinks, the Arabs take refuge in kief and other species of hemp. The native Mexicans cull the _peyotl_, the Siberians a toadstool, the Peruvians coca. 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.