In a speech in Parliament in defence of vaccination, Sir Lyon Playfair gave 4,000 per million as the average London death-rate by small-pox before vaccination—a number nearly double that of the last twenty years of the century, which alone affords a fair comparison. But far more amazing is the statement by the late Dr. W. B. Carpenter, in a letter to the _Spectator_ of April, 1881, that “a hundred years ago the small-pox mortality of London alone, with its then population of under a million, was often greater in a six months’ epidemic than that of the twenty millions of England and Wales now is in any whole year.” The facts, well known to every enquirer, are: that the very highest small-pox mortality in the last century in a year was 3,992 in 1772, while in 1871 it was =7,912= in London, or more than double; and in the same year, in England and Wales, it was =23,000=. This amazing and almost incredible misstatement was pointed out and acknowledged privately, but never withdrawn publicly! The late Mr. Ernest Hart, a medical man, editor of the _British Medical Journal_, and a great authority on sanitation, in his work entitled _The Truth about Vaccination_, surpasses even Dr. Carpenter in the monstrosity of his errors. At page 35 of the first edition (1880), he states that in the forty years 1728-57 and 1771-80, the average annual small-pox mortality of London was about 18,000 per million living. The actual average mortality, from the tables given in the Second Report of the Royal Commission, page 290, was a little over 2,000, the worst periods having been chosen; and taking the lowest estimates of the population at the time, the mortality per million would have been under 3,000. This great authority, therefore, has multiplied the real number by six! In a later edition this statement is omitted, but in the first edition it was no mere misprint, for it was triumphantly dwelt upon over a whole page and compared with modern rates of mortality.