First, I say, he did not fully reveal what he knew. In 1789 Jenner inoculated his son, Edward, an infant of 18 months, not with Cowpox, or with Horsegrease, but with Swinepox; and, according to the evidence of his own papers, the result was perfectly satisfactory. The child was subsequently inoculated with Smallpox on five or six different occasions, and always without effect. According to the well-known variolous test, he was proof against Smallpox. In short, there was nothing that Jenner ever adduced in favour of Cowpox that was not equally valid of Swinepox. And this Swinepox experiment was made nearly ten years prior to his advertisement of Cowpox and Horsegrease. Why, I ask, did he keep back the truth about Swinepox? When Cowpox was scarce, and every cow-house was explored for virus, why did he not recommend Swinepox as an alternative? Why, too, did he refrain from the obvious generalisation, that Cowpox, Horsegrease, Swinepox, and probably other sorts of pox, generated fevers, during the prevalence of which inoculation with Smallpox was not apt to take? The answer is plain, Because he had something to sell rather than something to teach. In conformity with this conduct he suffered the origin of Cowpox in Horsegrease, and the specific virtue of grease to be derided and denied. “It was fortunate for Dr. Jenner, and the triumph of his discovery,” wrote Dr. Mason Good, “that a minuter attention to the subject gave sufficient proof that there was no foundation for his opinion that Cowpox originated in Horsegrease, nor that any connection existed between the diseases.”[143] Such was the convenient medical verdict, which Jenner did not venture to disturb, though all the while persuaded of its error. There were failures to inoculate cows with Horsegrease, but Thomas Tanner, veterinary surgeon, of Rockhampton, Gloucestershire, “had the merit,” says Dr. Baron, “of proving the truth of Jenner’s statement.”[144] He succeeded in communicating the disease to the cow from the heel of the horse, producing on the cow’s teat a complete vaccine pustule. “From handling the cow’s teats,” said Tanner, “I became myself infected and had two pustules on my hand, which brought on inflammation, and made me unwell for several days. The matter from the cow, and from my own hand, proved efficacious in infecting both human subjects and cattle.”[145] Jenner distributed the virus from Tanner, and it operated precisely like Cowpox. But the proof did not rest with Tanner: others repeated his experiment with similar issues. Dr. Loy of Whitby published in 1801 _Some Observations on the Origin of the Cowpox_, in which he confirmed Jenner’s country tales, and described how (dispensing with the cow) he managed to inoculate patients with Horsegrease, producing pustules identical with those from Cowpox, and subjecting the persons thus equinated to the variolous test with complete impunity. Yet, with so much to fortify him, Jenner kept silent.