In the course of my inquiry, not a single instance occurred of any one having the disease, either casually or from inoculation, who on subsequent exposure to variolous contagion received the infection of smallpox.... Should it appear in the present instance that I have been led into error, fond as I may appear of the offspring of my labours, I had rather strangle it at once than suffer it to exist, and do a public injury. At present, I have not the most distant doubt that any person, who has once felt the influence of perfect cowpox matter, would ever be susceptible of that of the smallpox. Could universal conclusion be deduced from more questionable premisses? and this, too, by one who had just exclaimed, “How very few are capable of conducting physiological experiments!” Always, as we shall see; ungenerous toward those who questioned his assertions, Jenner wrote to his friend, Gardner-- This man, Ingenhousz, knows no more of the real nature of the cowpox than Master Selwyn does of Greek: yet he is among philosophers what Johnson was among the literati, and, by the way, not unlike him in figure-- When, in fact, what provoked him was that Ingenhousz knew too much about cowpox, and had laid his finger on the point of error at the outset. Inquiry on the part of Ingenhousz brought to light several other instances of smallpox after cowpox; and Dr. Pulteney of Blandford reported that Dorsetshire inoculators were familiar with the one sort of pox after the other sort. Jenner’s constant answer to such objections was, “Yes; but it could not have been true cowpox to start with”--a style of argument maintained with parrot-like persistency when smallpox followed vaccination. “Ah!” it was said, “there must have been some mistake about the vaccination; for no one can be thoroughly vaccinated and have smallpox.”