"These two figures deal with the +influence of the length of suckling on the birth-rate+, the longer the duration of the suckling period, _i.e._, the higher the number of children breast-fed for six months or more, the lower the birth-rate. This only holds good for the country (Curve B) not for towns (Curve A). This circumstance is explained by the fact that the voluntary restriction of births is much more frequent in towns than in the country, where consequently the influence of the length of the period of suckling on the birth frequency can find much stronger expression than in towns, where, as Curve A shows, it is entirely extinguished by artificial birth preventatives. From both tables it results that, to prevent the senseless waste of human life, the interval between every two births must be more than two years; further, that it is possible to increase it by breast-feeding; the number of births in a district is based in the main on the larger or smaller intervals at which the women of reproductive age have children, and it may, therefore, at the same time, be taken as an expression of these intervals. Keeping these two facts in view, and considering the influence of the mode of infant feeding on infant mortality, it appears to be in the interest of the race that by means of the long duration of breast-feeding, the birth intervals should be extended to at least two years. The facts established in these two tables have a considerable bearing on race-hygiene, especially in reference to the Neomalthusian contentions of the necessary inferiority of the later born, and as a confirmation of the utility of breast-feeding for the reduction of birth frequency. Extremely great appears the influence of breast-feeding on infant mortality."
This importance of breast-feeding is further illustrated by Figure C 74--+duration of breast-feeding and infant mortality+, after Dietrich; by Figure C 75--+average number of carious teeth+, after Bunge; and by the three figures, C 76, 77, and 78--"+average duration of breast-feeding and physical development, duration of breast-feeding and average school reports+, and +duration of breast-feeding and frequency of rachitic disturbances of development+," after the extensive and valuable researches by Röse.