3. _Great improvements in medical and in sanitary science are decreasing the death-rate and thus partly neutralizing the effects of a lower birth-rate._ The death-rate in a community is a fairly good index of its general welfare. The death of a large proportion of the children before they arrive at maturity indicates poverty or ignorance. The death-rate in the Middle Ages, especially in cities, was tremendously high, but during the last hundred years has steadily decreased. The race of man which, ever since the beginnings of volitional control, probably has had a smaller death-rate relative to the total number of individuals coming into existence than has any other species of living creatures, has to-day a far lower rate than ever before. Even in the most miserable industrial population where one half the children die before they are five years old, the death-rate is much less than among the young of the lion or the eagle. [Sidenote: The quality of population counts] 4. _Volitional control is acting with the greatest force in the more capable classes and thus threatens to reduce the quality of the population._ The quality of population is of more import than its quantity, alike in its economic, its social, and its ethical results. The productive force of a population is not measured merely by numbers. "Who" make up the population at any moment is no more a matter of indifference than "how many." One new-born child represents a negative addition to society, unintelligent, incapable, foredoomed to become a burden; another, with energy, thrift, inventive genius, comes to enrich and uplift his fellow-men. Quality counts for much. [Sidenote: Change in the American birth-rate] The average number of children reaching maturity in the families of the American colonists was six; the average number to-day in families of American descent is about two. Since many of these do not live to maturity, and of those who do survive many do not marry, the stock does not maintain itself in numbers. Much larger families are found among the poor whites of the mountains, the foreign population, the rate negroes, and, in general, in the lower ranks of labor. Forces are at work to sterilize or reduce in number the more intelligent elements of the population. The "new woman" movement, tempting into "careers," takes away from family life many of the women most worthy to become the mothers of succeeding generations, Self-interest is at war with the social interest. The individual asks, "Am I bound to sacrifice my comfort and happiness to the general good?" If this continues, the result must be a steady decline in the proportion of the population born of the successful strains of stock, and a steady increase of the descendants of the mediocre and duller-witted elements. [Sidenote: Rate of increase in the nineteenth century]