My inquiry into the nature of the Cowpox commenced upwards of twenty-five years ago. My attention to this singular disease was first excited by observing that among those whom in the country I was frequently called upon to inoculate, many resisted every effort to give them the Smallpox. These patients I found had undergone a disease they called the Cowpox, contracted by milking Cows affected with a peculiar eruption on their teats. On inquiry, it appeared it had been known among the dairies from time immemorial, and that a vague opinion prevailed that it was a preventive of the Smallpox. This opinion I found was comparatively new among them; for all the older farmers declared they had no such idea in their early days--a circumstance that seemed easily to be accounted for, from my knowing that the common people were very rarely inoculated for the Smallpox till that practice was rendered general by the improved method introduced by the Suttons: so that the working people in the dairies were seldom put to the test of the preventive powers of the Cowpox. Jenner’s design in the foregoing statement was manifest. It was to minimise the faith of the country folk, and to represent that by his own perspicacity he had discovered the virtue of Cowpox through his failures to inoculate with Smallpox. The inquiries of Pearson and others, however, showed conclusively that in many parts of the south of England, in Ireland, and on the Continent it was believed that to have suffered from Cowpox was to be secure from Smallpox; and the belief was entertained altogether independently of failures to inoculate with Smallpox; just as a similar belief prevailed among farriers as to the prophylaxy of Horsegrease. The faith in Cowpox was neither vague, nor new, nor confined to Jenner’s neighbourhood; and his assertion to the contrary showed with what hardihood he had undertaken to construct a case in his own favour. In opposition to the rural faith, medical men maintained that it was possible to have Smallpox after Cowpox; and surgeons averred that they had successfully inoculated many who had suffered Cowpox. Indeed it was indubitable professional testimony to this effect that compelled Jenner to forsake his first fancy for Cowpox, and to report the true specific as Horsegrease Cowpox. Having, however, to sacrifice that discovery, and revert to the Cowpox he had discredited, a fresh manœuvre was requisite; and thus was it performed--