When melancholia and mania are said to be due to heredity as one of the principal causes, the meaning intended is that in certain families the brain tissues are liable to be transmitted in somewhat impaired condition, and that through these brain tissues the mind will either not act properly, or under the stress of violent emotion, the loss of friends by death, or the loss of fortune, or serious disappointments in life, or a love affair, the already tottering mental condition will be overturned. In a word, it is not the direct transmission of insanity, but of a predisposition to the development of insanity under stresses and strains that is a matter of family inheritance. This is considered true now not only of mental but of all diseases. Not consumption, but the predisposition to it is inherited.
These considerations make clear how important this matter of heredity is. Physicians and students of anthropology are so much concerned about the increase of insanity as the result of the intermarriage of defectives that we are constantly reading in the newspapers of attempts at the legal regulations of marriage, so as to prevent further racial degeneration. Under present circumstances, any such legal regulation is probably impossible; but it seems perfectly clear that clerical influence should be brought to bear to discourage, as far as possible, intermarriage among those of even slightly disturbed mental heredity. Especially must any such idea as the possible beneficial influence of matrimony (for there are popular traditions to this effect) be unhesitatingly rejected and it must not be allowed to tempt those interested to look on such intermarriage with indifference.
Another and more serious question for the clergyman is that of the vocation in life of those who are weak mentally. By vocation is meant not only religious calling, but the occupation in life generally. Young people of unstable mentality and especially those of insane heredity should be advised against taking up such professions as that of actor or actress, or broker, or other life duties that entail excitement and mental strain. As far as possible they should be discouraged from taking up city life, and should be advised to live quietly in the country.