The latter influence is doubtless one that is nearly always at work, but it is wholly outside the scope of the present inquiry, and we shall therefore ignore it, save as it may appear incidentally. Nor does it require emphasis here; for the disastrous social and economic effects of alcoholism are patent to every observer. We find it most convenient to concentrate our attention first on the second of the questions above enumerated: to ask whether there is any good evidence that the use of alcoholic beverages by men and women really does originate degeneracy in their offspring.
To get such evidence, one must seek an instance that will be crucial, one that will leave no room for other interpretations. One must, therefore, exclude consideration of cases where a mother drank before child birth. It is well-known that alcohol can pass through the placenta, and that if a prospective mother drinks, the percentage of alcohol in the circulation of the unborn child will very soon be nearly equal to that in her own circulation. It is well established that such a condition is extremely injurious to the child; but it has nothing directly to do with heredity. Therefore we can not accept evidence of the supposed effect of alcohol on the fertilized egg-cell, at any stage in its development, because that is an effect on the individual, not on posterity. And the only means by which we can wholly avoid this fallacy is to give up altogether an attempt to prove our case by citing instances in which the mother was alcoholic. If this is not done, there will always be liability of mistaking an effect of prenatal nutrition for a direct injury to the germ-plasm.
But if we can find cases where the mother was of perfectly sound stock, and non-alcoholic; where the father was of sound stock, but alcoholic; and where the offspring were impaired in ways that can be plausibly attributed to an earlier injury to the germ-plasm by the father's alcohol; then we have evidence that must weigh heavily with the fair-minded.
An interesting case is the well-known one recorded by Schweighofer, which is summarized as follows: "A normal woman married a normal man and had three sound children. The husband died and the woman married a drunkard and gave birth to three other children; one of these became a drunkard; one had infantilism, while the third was a social degenerate and a drunkard. The first two of these children contracted tuberculosis, which had never before been in the family. The woman married a third time and by this sober husband again produced sound children."