_Hegar_ considers that there is hygienic justification for the limitation of the number of children to which a woman gives birth. The most suitable age for motherhood lies in his opinion between the ages of twenty and forty years. Childbirth in women younger or older than this entails too much danger both to mother and child. At least two and a half years ought to elapse between two successive births; and these figures give us eight as the maximum family. If we assume that the duration of pregnancy is nine months, and that of lactation nine to twelve months (or in cases in which the mother does not nurse her own infant, that a like period must be devoted to the careful supervision of the wet-nurse or of the methods of artificial feeding), we cannot consider it unreasonable to devote a further period of from six to nine months to the complete reestablishment of the woman’s health. “Moreover, woman does not exist solely for the purpose of subserving during two decades of her life the processes of reproduction. And to permit the maximum number of children to be as great as eight, we must presuppose that the woman is in perfect health, and that she lives in a perfectly healthy environment. Any illness or infirmity which renders the duties of housekeeping and the rearing of the existing family unduly difficult, indicates the need for a further limitation of child-bearing. And if the reproductive function is to be rationally controlled, we must above all attend to the age and the health of the parents. Occupation, habitation, and general environment have also to be considered. The correct ideal is indeed not difficult to discover.”