_Time of Birth, Seasons, and Meteorological Conditions._--Is it possible to demonstrate the existence of any connection between the time of birth and the temporal variations in the infantile death-rate? In the months in which the number of births is high, the infantile death-rate is probably also higher than at other times. This is true more especially of the very cold months, when infants cannot be taken freely into the open air; it is true also of the very hot months. It is well known that the annual curve of births exhibits two notable elevations--one in February and March, and the other in September; this depends on the fact that most conceptions take place, on the one hand, in the spring-time--that is, at the time of the general awakening of nature; and, on the other hand, in December, when nature reposes, and agricultural labours are at a standstill. But owing to the fact that the factors influencing infant mortality are so numerous and variable, it is not possible to demonstrate any definite relationship between the times of maximum births and the times of maximal infantile death-rate. The seasons and the meteorological conditions exert an influence upon infant mortality through the intermediation of their effect upon various social conditions. The infantile death-rate is highest during the summer, the rate in the months of July, August, and September greatly exceeding that in the other months of the year. During the hot season, contaminated and decomposing milk gives rise to fatal illness on all sides. When we compare different years, we find that the height of the infantile death-rate varies directly with the heat of the summer. This influence of the hot season is exerted almost exclusively upon artificially reared infants, and especially on those in whom the technique of artificial feeding is improper. It is an established fact that the children of the well-to-do largely escape a similar fate, simply because that in their case it is possible to keep the milk artificially cool, and to prepare it more carefully in other ways. CHAPTER IV THE QUALITY OF THE POPULATION; ARTIFICIAL SELECTION (EUGENICS) AND EDUCATION _Natural Selection and Artificial Selection._--The selective method practised by Nature works by means of the procreation of millions of individuals, and by the subsequent elimination of those individuals which are imperfectly or not at all adapted to their environing conditions; that is to say, natural selection operates repressively or destructively. Artificial selection, on the other hand, aims at preventing the procreation of individuals inadequately adapted to their environment; it deliberately eliminates those elements which are useless to society, or which can be utilised by society only at excessive cost: thus artificial selection is a preventive method.