Experience was not slow to demonstrate the futility of these assurances. At first the facts were flatly denied: it was impossible for smallpox to succeed cowpox. The evidence, however, grew too strong to be outsworn, and then it was said the cowpox must have been spurious. As failures accumulated over the operations of Jenner himself and his choice disciples (who were naturally presumed to know and avoid spurious cowpox) they began to lay great stress on the fact that smallpox itself did not always avert a subsequent attack; and if smallpox did not save from smallpox, why, they demanded, should cowpox be expected to do more?[194] Why, indeed! Still the cases of smallpox after cowpox were as scores to those of smallpox after smallpox, and then the argument was reduced to a competition between variolation and vaccination. “You inoculators with smallpox,” said the vaccinators, “are continually having smallpox after variolation, and why should we be expected to be more successful?” Why, indeed! The inoculators with smallpox in turn denied that after efficient variolation smallpox ever occurred, or could possibly occur; and thus the wrangle went on. One thing was plain and certain—the original claim of Jenner for the absolute infallibility of Horsegrease Cowpox as a preventive of Smallpox was reduced and surrendered bit by bit until it came to this at last—it made Smallpox milder!
These repeated surrenders were, however, never ingenuous. Mistakes are inevitable, and they are forgiven when frankly confessed; but frank confession was not Jenner’s habit. When vaccination failures had become notorious in 1808, he had the hardihood to assert, that from the outset he had recognised that as smallpox did not always avert smallpox, neither did he expect cowpox to do so; and cited as proof of his prescience this passage from Further Observations in 1799—
It should be remembered that the constitution cannot, by previous infection, be rendered totally insusceptible of the variolous poison; neither the casual, nor the inoculated Smallpox, whether it produce the disease in a mild or violent way, can perfectly extinguish the susceptibility.[195]
Here Jenner made a bold draft on his reader’s ignorance. It was his claim for horsegrease cowpox that it conferred an absolute security from smallpox without any qualification whatever. The assumed prescience in 1799 is completely belied when we refer to his arrogant manifesto of 1801. These are his words—
The scepticism that appeared amongst the most enlightened of medical men, when my sentiments on Cowpox were first promulgated, was highly laudable. To have admitted the truth of a doctrine, at once so novel and so unlike anything that ever appeared in the Annals of Medicine, without the test of the most rigid scrutiny, would have bordered upon temerity; but now, when the scrutiny has taken place, not only among ourselves, but in the first professional circles in Europe, and when it has been uniformly found in such abundant instances, that the human frame, when once it has felt the influence of the genuine Cowpox in the way that has been described, is never afterwards, at any period of its existence, assailable by the Smallpox, may I not with perfect confidence congratulate my country and society at large on their beholding, in the mild form of Cowpox, an antidote that is capable of extirpating from the earth a disease that is every hour devouring its victims; a disease that has ever been considered as the severest scourge of the human race![196]
Cowpox was thus set forth as a prophylactic with powers hitherto unknown and unique; so that Jenner was cut off from the claim of its equivalence with smallpox in character and consequences. He knew in 1799, as we have seen, that infection with smallpox did not render the constitution proof against the subsequent influence of the disease; but in 1801, as we see, it was his express contention that what smallpox failed to do that cowpox did—it protected the constitution perfectly and for ever from smallpox, and nothing to compare with it had ever appeared in the Annals of Medicine. It was only under the pressure of exposure and defeat that he humbled himself to write to Dunning, 1st March, 1806—
The security given to the constitution by Vaccine Inoculation is exactly equal to that given by the Variolous. To expect more from it would be wrong. As failures in the latter are constantly presenting themselves, we must expect to find them in the former also.[197]
To this pass was the infallible preservative from smallpox, with nothing to match it in the Annals of Medicine, reduced within the experience of seven years!
The most thorough-going and far-reaching of Jenner’s excuses for vaccination failures were herpetic affections of the skin. In his journal we read—
Inoculated C. F. a second time. It is very evident that the affection of the skin called red gum deadens the effect of the Vaccine Virus. This infant was covered with it when inoculated four days ago. The same happened with Mrs. D.’s infant.[198]