Pearson foresaw that if the principle of inoculation with Cowpox were established it would lead to other applications—
The Cow Poison appears to alter the human constitution, so as to render it insusceptible of a different morbific poison, namely, the variolous in producing the Smallpox. This fact is, I believe, quite a novelty in physiology and pathology: it indicates a new principle in the mode of prophylactic practice. And we now see a principle upon which diseases from various other morbific poisons may possibly be prevented from taking place, such as the Measles, Ulcerous Sore Throat, Hooping Cough, Syphilis, etc., namely, in consequence of destroying the excitability of the constitution to such poisons by the agency of different, and perhaps less hurtful ones. Whether the Cowpox preserves the constitution from other morbific poisons, besides the variolous, is an undecided question. (P. 79.)
Like Jenner, he also recognised in Cowpox a counter-irritant—a safe sort of fever that might be used to drive off other diseases—
If it be true that the same constitution is liable to undergo repeatedly the Cowpox, to which distemper no one has fallen a victim, practitioners may avail themselves of this means of exciting an innocent fever as a remedy of various disorders; it being a truth, admitted by men of experience, that fevers are occasionally efficacious remedies, especially for inveterate chronic maladies, such as Epilepsy, Hysteria, Insanity, St. Vitus’s Dance, Tetanus, skin deformities and diseases, etc. (P. 81.)
Nor was the notion without warrant, for Smallpox itself was credited with a double action as a generator and exterminator of disease—
A disposition to certain diseases, and even diseases themselves, are not rarely brought on by the Smallpox; but sometimes also dispositions to diseases, and diseases themselves of the most inveterate kind are removed by the Smallpox. (P. 77.)
In one respect, Jenner showed himself superior to Pearson, namely, in offering some explanation of Cowpox. Pearson accepted the disease on the rural terms—as an eruption on Cows attended with no serious illness. If in any way such Pox was equivalent to Smallpox, it was inexplicable that it should be limited to the udder and teats of milch cattle, and that males, and females not in milk, should be exempt from infection. A disease so unique wanted accounting for; but Pearson made no attempt to account for it, nor gave any sign that he apprehended the difficulty. Jenner, on the other hand, accounted for Pox on the Cow by referring it to infection from the Horse conveyed by the milkers, which explanation Pearson rejected. But in giving Jenner credit for so much, let it not be for over much. Whilst he ascribed Cowpox to a credible cause, he did not recognise his advantage and summon gainsayers to explain how Cowpox, as described by them, could exist without Bullpox. On the contrary, as we shall see, Jenner submitted to be silenced on this point for reasons far from creditable.
FOOTNOTE:
[105] An Inquiry concerning the History of the Cowpox, principally with a view to supersede and extinguish the Smallpox. By George Pearson, M.D., F.R.S., Physician to St. George’s Hospital, etc. London, 1798, 8vo., pp. 116.