As the first half of the 1800s was drawing to a close, the conquest of pain seemed no closer than it had been a century earlier when English anatomist John Hunter sniffed that the surgeon was little more than "a savage armed with a knife."17 All the false starts of the past, however, were about to culminate in a demonstration on October 16, 1846, that would change the world of medicine forever.

The demonstration was the final link in a chain of events that began two years earlier, when Dr. Horace Wells, a dentist in Hartford, Connecticut, attended a laughing gas exhibition-one of the public spectacles to which anesthesia had been relegated. A friend, Sam Cooley, while cavorting about the stage after inhaling the gas, ran hard into a wooden bench, apparently not realizing it.

When Cooley returned to his seat, Wells noticed blood on his friend's trousers...