Absurd as was the extension of the ratio of London smallpox to the populations of the United Kingdom, of Europe, and of the world, the London disease itself afforded little warrant for the extreme terms of horror and dismay with which it was described. Smallpox did not increase the death-rate of London: when smallpox was most prevalent and least prevalent, the total mortality was but slightly affected. As long as the sanitary conditions of the great city remained unchanged, fevers replaced smallpox and smallpox replaced fevers, and whether deaths were from one form of disease or another, so that the people died the same, what did it matter? Smallpox when most prevalent was never accountable for much more than 10 per cent. of the total London mortality, and in some years for less than 3 per cent.; and it is to be remembered that the larger portion of that mortality was infantile mortality--smallpox being in the great majority of cases a disease of the young; none the less objectionable on that account, but less chargeable than some other forms of zymotic disease with striking down the adult bread-winner and enlarging misery and pauperism. Again, in much of the talk about smallpox, it was assumed that the disease had no limits--that it was something like fire, and might spread to any extent if unchecked. But what was there to justify such an assumption? Assuredly nothing in London experience. Smallpox was always present in London, waxing and waning under some unknown law; the deaths rising as high as 3992 in 1772 and falling as low as 522 in 1797--the extremes of the century. Why did 4000 never die in any year, or 7000, or 10,000? When a fire is extinguished, we know it has met with a check; and if smallpox caused 3992 deaths in 1772 and 522 in 1797, and smallpox be like fire, there was, we see, a check; and I ask, What was that check? There may be answers, but none for unreserved acceptance. What is certain is, that in London smallpox was never an illimitable affliction. It had limits, and it was only in the rhetoric of alarmists that it had none. And the check to the disease (whatever it was) lay in the bodies of the citizens, and not in their therapeutics. Isolation was rarely attempted, and in their crowded habitations was impracticable. Moreover they had not only the smallpox appropriate to their evil conditions to contend with, but the disease as propagated and diffused by the inoculators. What we have to say is, that whilst in the London of last century we behold smallpox endemic and cultivated, yet in no year did the mortality therefrom exceed 4,000; and further, that with so much to favour and stimulate the disease it was a diminishing quantity. In the words of Dr. Farr-- London Smallpox attained its maximum mortality after inoculation was introduced, and the disease began to grow less fatal before vaccination was discovered.