The drug-induced blocking of pain or sensation — in general anesthesia usually with unconsciousness, in local or regional anesthesia while the patient stays awake — that makes the inside of a living body operable. Before it arrived in the 1840s, surgery was a race against a conscious, struggling patient, and a surgeon's chief skill was speed. Anesthesia, paired with antiseptic methods against infection, turned the operating table from a scene of brief horror into the calm center of modern medicine, while opening a scientific mystery about consciousness that remains unsolved.
Before the 1840s, surgery meant cutting into a fully awake person held down by strong assistants, and the best a surgeon could offer was speed: the fastest could amputate a leg in under a minute. Ether changed that on October 16, 1846, when a Boston dentist put a patient to sleep and a surgeon cut without a sound from the table. Yet in those same decades, enslaved Black women were operated on again and again without any anesthesia, on the racist false claim that they felt less pain. The mercy was real, and it was not handed to everyone.