The most important means for the diminution of child mortality is to improve the conditions of working-class life. It is indisputable that the more prosperous members of the working class have fewer children on the average than those who are not so well off; that in any region in which an improvement has taken place in the conditions of working-class life a fall in the birth-rate has ensued; that the poorer the condition of any stratum of the proletariat, the larger is the average family. An increase in the average working-class income will lead to a proportionately greater decline in the death-rate of infants and young children. For this increase in income will operate in two ways: in the first place, if the number of children remain the same, the rise in income will ensure for each child a larger share of the necessaries of life; and, in the second place, with the rise in income the size of the average family will diminish, and this will reduce the child mortality. Inasmuch as the height of the infantile death-rate depends mainly upon the great infant mortality among the lower strata of the population, every effort at reform in this direction must begin at the lower end of the social scale. _Child Mortality in the Towns._--A connection appears to exist between density of population and the death-rate: if the other conditions remain unchanged, the death-rate increases _pari passu_ with increasing density of population. The question whether in the towns child mortality is higher than in the country districts has not yet been decisively answered; and it is equally uncertain whether from the hygienic standpoint the existing rural conditions are better than the urban. It appears probable that child mortality is higher in the towns than in the country districts; it is more doubtful, however, if the same can be said of infant mortality. The statistical data available on this question must be subjected to a stringent critical examination. The infant mortality which truly belongs to the towns appears smaller than it really is, for the reason that a proportion of the infants born in the towns are placed in the care of foster-parents living in the country, and some of these die in the country. It is equally true that many people from the country die in hospitals and other institutions in the towns; but this applies much more to adults than to children.