In the Talmud, Rabbi Joshua gives the following advice regarding early marriage in Jewish girls: “If your daughter has attained puberty and is twelve years and six months old, she must be married at any cost. If no other means are available, manumit one of your slaves, and give her to the freedman to wife.”

Experience proves, however, that in our climate, at any rate, girls who marry at a very early age are inferior in fertility to those who refrain from marriage until the genital organs have attained complete maturity; and statistics show that those women who marry before attaining the age of twenty must wait longer for their first pregnancy than those who marry between the ages of twenty and twenty-four. At the higher age also, women bear parturition and its consequences more easily than those who marry very young. A similar influence in marriage to that resulting from undue juvenility is exercised by its opposite, marriage when a woman is already elderly; in this case fertility is limited, and health also is especially apt to suffer. When the indications of the climacteric are clearly apparent, marriage is contra-indicated, not only on account of the impossibility of fertilization, but also in respect of its general unsuitability in the closing stage of the sexual life.

Not only is the absolute age of the woman of importance in deciding on the advisability of marriage, but the relative ages of the proposed husband and wife must also be taken into account, first of all in respect of the wife’s possible fertility, and secondly in respect of her general health. The most suitable arrangement is that in which there is no marked difference in age. The husband may be, and indeed in existing social circumstances almost necessarily is, somewhat older than his wife, as much perhaps as eight or ten years. But a very great disparity of age (in either direction) is a serious error. If a very young girl marries an elderly man, or a developed matron marries a young man, the true purpose of marriage is unfulfilled, the eternal laws of nature and all ethical principles are infringed. In the breeding of animals, the fundamental principle has long prevailed that the animals chosen for coupling should be well suited each to the other and should be in perfect physical condition; and breeders are also familiar both with the favorable influence of good nourishment and with the advantage of the opportune crossing of distinct varieties. The same principles are equally applicable to the human race, neglected as they commonly are in practice.

With regard to the marriage of near kin, we can only remark that the marriage of those closely related by blood should as far as possible be avoided, and that such a marriage must be absolutely prohibited when in both families there is a history of tuberculosis, mental disorders, diabetes, and the like. When first cousins contemplate marriage, it is indispensable, not only that both individuals should be in perfect health, but also that on neither side there should be any serious family history of transmissible disease or transmissible morbid tendency; and, further, it is absolutely necessary that no such marriage of near kin should have taken place in the proximate ancestry of the cousins, i. e., their cousinship must not be a double one, derived both from the paternal side and the maternal. It is indeed to be recommended, with a view to the production of a healthy and powerful posterity, that marriage should bring about a crossing of healthy individuals proceeding from different families, different places, and different constitutional types. An instance of the advantage to be found in this practice is pointed out by Ribbing, who shows that the most powerful aristocracy in Europe, that of England, by the gradual creation of new peers, on the one hand, and by the gradual decline of younger sons and their descendants into the middle class, on the other, has undergone a continual crossing with less exalted but originally sounder stocks; in this way its vigor and fertility have been maintained, in contrast to the nobility of many continental states, which has so largely perished, in consequence of its exclusiveness in the matter of marriage.

“In this connection,” continues Ribbing, “we must bear in mind, that blood-relationship is not the only matter that has to be considered; in the interest alike of the family, and of society, it is necessary to demand that certain degrees of relationship by marriage alone, should fall within the ‘prohibited degrees’ of love and marriage. There are certain groups related by marriage and held together by the bond of affection, from which foster-parents and guardians may most suitably be selected to fulfil the duties as regards education and training of children who have been orphaned in early years. For such a purpose none seem better adapted than the brothers and sisters of the deceased parents; but the upbringing of the children can be confidently entrusted to the former only if the relationship between the older and the younger branches of the family is one regarded by law, and still more by morality and custom, as one precluding the possibility of the occurrence of sexual love and marriage.”

Möbius, writing on “The Ennobling of the Human Race by Selection in Marriage,” observes: “The most important aim of natural development is the perfection of humanity. The qualities of the coming generation depend for the most part upon the qualities of the parents. Marriage from affection ensures the fulfilment of nature’s aims with more security than marriage from reason; since what we have to think of is not the happiness of the married pair but the quality of their children. Of great importance, also, to the development of the human race are the conditions during the commencement of life, and the mode of education. The improvement of the race has not hitherto been the conscious aim of the generality of people. The law does not as yet, as it should, take into account the advantage of posterity. Capital punishment is fully justified and purposive. Criminals should not be allowed to marry. The perpetuation of disease by inheritance should be checked by the utmost powers of the state. Any one marrying while suffering from any venereal disease still in an infective condition should be punished. The marriage of persons suffering from tuberculosis should be prohibited. For the prevention of disease is more important than its cure. The most important factor in preventive medicine is an improvement in the conditions of life. The human ideal should be, goodness of heart in association with physical and mental health. Goodness, beauty, and strength should be simultaneously pursued. Since, however, man is made by birth far more than by education, selection in marriage is of fundamental importance. In the choice of a partner, attention is rightly paid to beauty, since beauty and health are fundamentally identical; moreover, a human being endowed with beauty is usually also more moral than one devoid of that attribute. Equality of birth is as a rule desirable in marriage; but not the family only is to be considered in determining the existence of such equality, individual characteristics must likewise be taken into account. Whether the crossing of races is desirable is not yet certainly determined.”

From the hygienic standpoint it is necessary that in marriage also the frequency and the manner of sexual intercourse should be regulated.

Wise men and lawgivers of all the nations of antiquity have insisted upon the necessity of certain intervals between the acts of intercourse. Thus, Mahomet prescribed 8 days, Zoroaster 9 days, Solon 10 days, Socrates also 10 days. Moses forbade intercourse during menstruation and for a week after the cessation of the flow. Luther prescribed intercourse “twice a week.”

Birds and many mammals are competent to perform intercourse at exceedingly short intervals. A well-bred cock will repeat this act 50 times daily; a sparrow, 20 times in an hour; a bull, 3 to 4 times in an hour. In the human species, however, too rapid repetition of intercourse is deleterious not only to the male, but to the female also, though the latter certainly suffers in less degree. For in this act the female plays a more passive part, and for this reason can repeat it with impunity more frequently than the male, who loses semen at each repetition. It is not possible, however, to lay down precise rules as to the permissible frequency of intercourse in either sex; the matter must depend upon physical needs. Moderate and regular indulgence in sexual intercourse is unquestionably advantageous to women both physically and mentally, regulating all the functions of the body, and tending to produce a contented and cheerful frame of mind.

During menstruation, a woman should refrain from intercourse. By the Mosaic law the death punishment was allotted both to the man and to the woman who indulged in coitus while the latter was menstruating. As a matter of fact, considerations alike of hygienic cleanliness and of sanitary precaution prohibit the performance of coitus during this period. Severe menorrhagia, perimetritic irritation, and parametritic inflammations, have been observed to follow such indiscretions. On the other hand, it is more than doubtful whether, in the event of pregnancy resulting from intercourse performed during menstruation (and conception is especially apt to occur at this time), the child is likely, as earlier authors maintained, to be unfavorably affected, and to suffer from cachexia, scrofula, or rickets.