Bristol, 3rd October, 1798.
I wish you had been able to have communicated the cowpox to the cow by means of inoculation from a greasy horse’s heel, for your work would then have been more complete and satisfactory.
I do not see that you need hesitate to accept the invitation given you to inoculate with the cowpox, convinced as you are that it will secure the persons so inoculated from ever being infected with the smallpox.
Everlasting security from smallpox! Such was the unqualified promise, and with how little warrant! In presence of a Socratic inquirer with his persistent, how do you know? Jenner must have stood confounded.
A letter to Jenner from Dr. Percival, also contains some remarks worth notice. He wrote—
Manchester, 20th November, 1798.
The facts you have adduced incontestably prove the existence of the cowpox, and its ready communication to the human species. But a larger induction is yet necessary to evince that the virus of the Variolæ Vaccina renders the person who has been affected with it secure during the whole of life from the infection of the smallpox.
Mr. Simmons, an ingenious surgeon of this town, has inoculated a human subject with the ichor issuing from what is termed the grease in horses; but the fluid introduced, though eight punctures were made, neither occasioned inflammation nor eruption; yet the same child was soon afterwards inoculated with success for the smallpox. Mr. Simmons has now engaged a herd of cows, and is busily employed in making such experiments as your publication has suggested.
It is very remarkable, that the cowpox has been hitherto unnoticed in Cheshire, which is not less a dairy county than Gloucestershire, and where the office of milking is performed also by men and maid servants indiscriminately.