Cowpox children. In 1796, British medical practitioner Edward Jenner tested the theory that cowpox could protect someone from being infected by smallpox. Although cowpox originates on the udder of cows, Jenner took his sample from a milkmaid, Sarah Nelmes. Jenner extracted the pus of one of the lesions formed by cowpox on Nelmes to another individual who never had smallpox, James Phipps. He eventually developed a scab and fever that was manageable. Approximately six weeks later, Jenner then introduced an active sample of the smallpox virus into Phipps to test the theory. After being observed for an extended amount of time,
Edward Jenner these cases the severity of the illness was notably diminished by previous vaccination. In 1821, he was appointed physician extraordinary to King George IV, and was also made mayor of Berkeley and justice of the peace. He continued to investigate natural history, and in 1823, the last year of his life, he presented his "Observations on the Migration of Birds" to the Royal Society. Jenner was found in a state of apoplexy on 25 January 1823, with his right side paralysed. He never fully recovered and eventually died of an apparent stroke, his second, on 26 January 1823, aged 73.