I have had repeated opportunities lately of pointing out this satisfactory distinction to the parents of children who were affected with Small Pox, both after Vaccination and when no such protecting influence had been employed. The contrast between the characters of the disease, as evinced in these different individuals, was too striking not to carry immediate conviction to the minds of all present; and I believe it has been of considerable service in inducing many to have their children vaccinated, who would otherwise have omitted it altogether. These cases occurred among the lower orders of society; and I feel assured that this demonstrative proof of the utility of Vaccination will do more to remove the prejudices of these people than any abstract reasoning from facts of which they have not themselves been witnesses, however numerous and well authenticated. I should, therefore, strongly recommend it to every practitioner to take advantage of any opportunities that may be afforded him of pointing out this most marked distinction between the natural and modified Small Pox. ------------------------------------------------------------------------ CHAP. I. We shall best estimate the value of any means of removing an evil, by enquiring, in the first place, into the extent of the effects of the evil which it is our object to remove. And we shall also form the most correct estimate of the value of the means which have been employed for its removal entirely, or in part, by reverting to its extent previous to the employment of such means, and comparing the amount of its former ill consequences, with those which are still produced by it. To satisfy ourselves on the subject of the present enquiry then, it will be useful to put the following queries:—1st. What were the destructive consequences of Small Pox previous to the introduction of Vaccination? And, 2ndly, What influence has Vaccination exerted over these consequences—1. by extensively superseding the cause—and 2. by essentially interfering with the effect? To answer the former question satisfactorily, it will be necessary to enter, at some length into the history of Small Pox, before Vaccination was proposed as a means of prevention. But it will be remembered, that previous to that era, a means had been already long in use, for the purpose of diminishing, at least, the danger of this terrific disease; and that for half a century the Small Pox had been communicated to thousands annually by inoculation, with the view of accomplishing this very desirable end. This will naturally give rise to a second division of the history of Small Pox. Our first enquiries will therefore be directed to the time antecedent to the use of inoculation for Small Pox, when no artificial measures were adopted for protecting mankind from its fatal attacks.