_The Age of the Parents._--The age of the parents at the time of procreation has a marked influence upon the health of the offspring. The parents should not be too young. It is not well that the mother should be less than twenty, or the father less than twenty-four years of age. Many of the children of such extremely youthful parents are weakly, and have poor health. On the other hand, the parents should not be very old. When the mother is over forty and the father over fifty years of age, the children are apt to be weakly; also they are apt to be left orphaned at a comparatively early age. It is also undesirable that there should be a great difference between the ages of the parents. Thus the parents should be young, but not too young. The younger they are, the more children can they procreate--first of all, because their fertility is greater in youth, and, secondly, because their married life lasts longer. Qualitatively, also, the children of such marriages are usually healthier. As a matter of fact, the age indicated is the normal age for marriage--the age at which the great majority enter upon marriage. _The Marriage of Near Kin._--We still lack precise information to enable us to decide whether the marriage of near kin is injurious to the offspring of such marriages. According to certain (unofficial) statistics, of 1000 marriages, from 7 to 11 are those of persons near akin. Naturally, in certain remote and inaccessible districts, the proportion of such marriages is greater than this. Two very different views have been put forward by scientific authorities. According to one school, the marriages of persons near akin either prove completely sterile, or else produce offspring defective in body or in mind. According to the other school, blood relationship has _per se_ no influence upon the offspring of the unions of nearly-related persons; where the parents (in such marriages) are themselves free from defects transmissible by inheritance, there is no reason to anticipate that the offspring will be in any way defective, unless other noxious influences (in addition to the kinship of the parents), such as disease, debility, exhaustion from previous excesses, &c., have been at work. But if such noxious influences have affected both parents, the danger of some congenital defect appearing in the children is very great. We certainly see many cases in which the marriage of near kin results in the procreation of large and thoroughly healthy families; but, in contrast with these, we also see many cases in which the offspring of such marriages have proved non-viable or degenerate (especially, blind, deaf-mute, idiotic, insane, polydactylous, or affected with congenital developmental defects).