But we are rapidly diminishing those selective agencies which in the past have developed race vigour. As we shall presently see, skill in nurturing the sickly has, in modern times, wonderfully reduced the mortality amongst infants; improvements in methods of nursing, the replacement of cotton by flannel and wool, and the use of many foods, some of them artificially digested, gives a sickly infant a chance of living, and it survives its first most dangerous years. Then its chances are again improved, for the infective diseases are being held in check, and it has comparatively little to fear from them. Thus it survives and lives to adult age, when, like the hothouse plant, it is still protected from hardships to which the race had formerly been freely exposed. It lives to lower the average physique of the mothers or fathers who produce the next generation of children. This increased preservation of the sickly has had the effect of increasing the life period of an average child, and this increase in the life probability is often and very rightly cited as an indication of the improved sanitary conditions of the people. Improved sanitary surroundings, as we have seen, are taken advantage of chiefly by the sickly, and thus with our increased probability of life we have diminished the average robustness of constitution, or innate healthiness of the race, for a larger proportion of sickly ones are living amongst us. In our day a greater number of parents suffer from phthisical, scrofulous and other taints than in days gone by, and these and other taints are passed on to their children. So far we have seen what of necessity follows from our biological premises, but it is also possible, I think, to show by statistics that already very observable deterioration has taken place. _Births, Deaths, and Marriages._ If we examine one of the reports of the Registrar General for births, deaths and marriages, we shall gain pretty full information concerning the deaths from disease, accident, old age, etc., that have occurred during the last thirty or forty years. _Increase of Constitutional Weakness._