The Cowpock, 1802, by James Gillray. Dr. Edward Jenner used cowpox to vaccinate against smallpox. Gillray shows the result: immediately upon being vaccinated, Jenner's patients sprout cows. In this instance the satirist's disdain was misplaced; Jenner was on to something.
Courtesy of the Harvard Medical Library/Francis A. Countway Library of Medicine.