Let us now examine the lowest line, showing the small-pox death-rate. First taking the period from 1760 to 1800, we see, amid great fluctuations and some exceptional epidemics, a well-marked steady decline which, though obscured by its great irregularity, amounts to a difference of 1,000 per million living. This decline continues, perhaps somewhat more rapidly, to 1820. From that date to 1834 the decline is much less, and is hardly perceptible. The period of Registration opens with the great epidemic of 1838, and thenceforward to 1885 the decline is very slow indeed; while, if we average the great epidemic of 1871 with the preceding ten years, we shall not be able to discover any decline at all. From 1886, however, there is a rather sudden decline to a very low death-rate, which has continued to the present time. Now it is alleged by advocates of vaccination, and by the Commissioners in their Report, that the decline from 1800 onwards is due to vaccination, either wholly or in great part, and that “the marked decline of small-pox in the first quarter of the present century affords substantial evidence in favour of the protective influence of vaccination.”[8] This conclusion is not only entirely unwarranted by the evidence on any accepted methods of scientific reasoning, but it is disproved by several important facts. In the first place the decline in the first quarter of the century is a clear continuation of a decline which had been going on during the preceding forty years, and whatever causes produced that earlier decline may very well have produced the continuation of it. Again, in the first quarter of the century, vaccination was comparatively small in amount and imperfectly performed. Since 1854 it has been compulsory and almost universal; yet from 1854 to 1884 there is almost no decline of small-pox perceptible, and the severest epidemic of the century occurred in the midst of that period. Yet again, the one clearly marked decline of small-pox has been in the ten years from 1886 to 1896, and it is precisely in this period that there has been a great falling off in vaccination in London from only 7 per cent. less than the births in 1885 to 20·6 per cent. less in 1894, the last year given in the Reports of the Local Government Board; and the decrease of vaccinations has continued since. But even more important, as showing that vaccination has had nothing whatever to do with the decrease of small-pox, is the very close general parallelism of the line showing the other zymotic diseases, the diminution of which it is admitted has been caused by improved hygienic conditions. The decline of this group of diseases in the first quarter of this century, though somewhat less regular, is quite as well marked as in the case of small-pox, as is also its decline in the last forty years of the 18th century, strongly suggesting that both declines are due to common causes. Let any one examine this diagram carefully and say