It is for me to establish these assertions.
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. He preferred to be adjudged mistaken rather than risk the forfeit of public favour and pay. Nor might I blame him, had he frankly reasserted the integrity of the Gloucestershire faith, and allowed that since the public were ready to accept Cowpox without Horsegrease, it was not for him to stand in the way of their preference by an obstinate defence of what was non-essential in practice.
But the case for Horsegrease was yet stronger than I have stated. Dr. Sacco of Milan was sometimes described as “the prince of vaccinators” by reason of his enthusiasm, his professional attainments, and the facilities that were accorded to him in the Cisalpine Republic of those days for universal vaccination. He tried to generate pox on the cow with grease from the horse, but failed, and in 1801 reported to Jenner his failure. In 1803, however, he cried, Eureka! A coachman presented himself at the Milan Hospital suffering from an eruption contracted in grooming a horse with greasy heels. He was at once led off by Sacco to the Foundling Asylum, where nine children were inoculated from the vesicles on his hands. On three of the children the inoculation took, producing vesicles which were pronounced to be the same as those resulting from Cowpox. The virus was propagated from arm to arm, and distributed in all directions. Dr. Sacco from thenceforth avowed himself a Horsegreaser. “It is now admitted and settled,” he wrote to Jenner from Milan, 25th March, 1803, “that grease is the cause of vaccine, and we cannot too soon alter the designation to equine.”
Was the designation changed to equine? It was not, nor was the attempt made. Those chiefly concerned in promoting vaccination in England would not hear of Horsegrease, and many were ready to swear that in the matter of pox, the horse and the cow had no connection whatever, and that Jenner had too hastily assumed the truth of a vulgar west country opinion.
Dr. De Carro of Vienna, who described himself as Jenner’s friend and first apostle, having effected the first vaccination on the Continent and transmitted the first charge of vaccine to India, was also a Horsegreaser. Whilst Jenner was judiciously holding his tongue about Horsegrease in England, he wrote to De Carro congratulating him on his success in conveying Cowpox to the East, and ascribing the failure of the English attempts to the absurd prejudice against Horsegrease, which Dr. Loy had, however, completely annihilated. Here are his words under date, 28th March, 1803—
I am confident that had not the opponents of my ideas of the origin of the disease been so absurdly clamorous, particularly the par nobile fratrum [Pearson and Woodville], the Asiatics would long since have enjoyed the blessings of Vaccination, and many a victim been rescued from an untimely grave. The decisive experiments of Dr. Loy have silenced the tongues of these gentlemen for ever.[146]
How the clamorous opposition to Horsegrease had deprived Hindoos of the earlier blessing of vaccination, we are left to conjecture. Perhaps he meant that Horsegrease would have borne transit to India better than Cowpox, or that the Hindoos themselves might have resorted to horses with greasy heels.
In reply, 22nd April, 1803, De Carro wrote to Jenner commending his moderation in maintaining silence toward his antagonists—little apprehending the motives of that silence. Pearson’s conduct, he thought, bordered on insanity. “I am extremely glad,” he continued, “that you have treated it with the contempt it deserves, though I am happy to see that your friends have exposed his ridiculous and malevolent designs.”
De Carro was intimate with Sacco of Milan, and from him received virus derived from Horsegrease, which he used indiscriminately with Cowpox, until in Vienna it was unknown who were vaccinated and who equinated.[147]