It is of still more importance, however, to know, that when Small Pox has occurred after Vaccination, it has been so essentially altered in the severity of its symptoms, and in the degree of danger arising from it, as to have rendered it entirely harmless in almost every instance; and although fatal cases have taken place in a few insulated and peculiar examples, they have been very much more rare than those which have occurred in consequence of inoculated, or even of secondary Small Pox. Sir Gilbert Blane, after describing (p. 10-11) the mild character of the disease as occurring after Vaccination, continues thus—“What forms the strong line of distinction from proper Small Pox is, that, with a few exceptions, it does not advance to maturation and secondary fever, which is the _only period of danger_. I am not prepared to deny that death may have occurred in a few instances; nay, there seems sufficient evidence that it actually has; but then adverse cases are so rare as not to form the shadow of an objection to the expediency of the general practice. A few weeks ago, at a meeting of this (the Medical and Chirurgical) Society, at which forty members and visitors were present, I put the question, whether any of these eminent and extensive practitioners had met with any fatal cases of this kind. Two gentlemen had each seen a _single case_, and two other gentlemen took occasion to say, that they had each seen a case of _second Small Pox_—both of which proved _fatal_.” And Dr. Thomson tells us (Historical Sketch, &c. p. 279), that “since the publication of my ‘Account of the Varioloid Epidemic,’ I have seen above _two hundred_ additional examples of Small Pox in Edinburgh, making in all _eight hundred and thirty-six_ cases of this disease, which have come under my observation since June, 1818. Of the whole number, _two hundred and eighty-one_ have occurred in individuals who had neither had Small Pox nor Cow Pox, and of these fully more than _one_ in _four_ died; _seventy-one_ had previously passed through _Small Pox_, and of these _two_ have died; and _four hundred and eighty-four_ had undergone the process of _Vaccination_, and of this number _one_ only died; results (adds Dr. Thomson) which evince, beyond the power of cavil, the beneficial effects of Vaccination in protecting the human constitution from the dangers of Small Pox, and the great advantages which must ultimately arise from the universal adoption of this practice.”—Perhaps the most fatal epidemic Small Pox, which has occurred of late years, was that which took place at Norwich in 1819. A history of it was published in the following year by Mr. Cross, and the general result was in perfect accordance with Dr. Thomson’s experience of the epidemic at Edinburgh.