Perhaps rather than a puzzle, the discovery of anesthesia can be compared to a road leading up a steep hill. Following scientific signposts along the way, investigators repeatedly seemed poised to reach the summit only to turn aside just short of their goal out of concerns about the safety of the substances they were studying. The substances-nitrous oxide, ether, and morphine-would eventually become effective anesthetics, but, ironically, they were first used for recreation. As a result, humanity had to wait half a century or more for blessings of anesthesia. Ether, the anesthetic that would at long last gain the attention of the medical community and then the world, was discovered some six hundred years beforehand. Scientist and philosopher Ramon Llull, working sometime in the 1200s, combined alcohol with sulfuric acid, thereby producing a white fluid. Since the new substance had a strong...