But blood-relatives are vastly more likely to inherit a similar diathesis--indeed, are quite sure to do so, if it be one of unhealthy character,--and the atavic influences would also be similar; so that any counteracting effect through this influence would be much less between blood-relations than with others, and would probably be the greatest when no such relation exists. Here, then, becomes apparent the danger arising from consanguineous marriages, _i. e._, that of perpetuating and intensifying unfavorable physical and mental traits, which may be alike on both sides. Where no such relation exists, there is a great probability that other counteracting qualities of character and hereditary influences may modify and even remove weaknesses, while, with such a relation existing, there is every probability that weaknesses or tendencies toward disease, both physical and mental, whether inherited or acquired, will become greatly increased. Therefore, as there exist in many families, undesirable traits of character, both physical and mental, a removal or diminution of which is desirable; and as there is a greater probability that this can be more surely done, of whatever nature they may be, by introducing other and opposing tendencies from unrelated families, it would appear to be highly important, as a rule, to discountenance marriages of persons who are related to each other by ties of blood. CHAPTER X. ALCOHOL. Of the several individual factors, which are especially potent, as tending to develop and perpetuate the Insane Diathesis, there are none which can be regarded as more influential, either directly or indirectly, than alcohol. Over-education of the brain, under-education, and heredity, all may exert an influence which tends toward this result, and their victims may be found in large numbers in all our asylums and hospitals; but the effects of alcohol are so insidious, it has been so generally used in the past, and its effects are so often transmitted to succeeding generations, that probably the sum total of its effects are far greater than those of either of the above-named agencies.