While the patient was just told to quit whining by the now inebriated doctor.
So in those days, a merciful surgery was a fast surgery. When the gangrene fairy hit your house and the leg had to come off, the best you could hope for was a surgeon with sharp instruments, a lightning-quick hand and careful precision.
Robert Liston had the first two.
Liston could amputate your whole leg in less than three minutes -- skin, bone, muscle, tendon, right through. When every second is filled with excruciating pain and blood loss, that speed had to have made Liston seem like an angel of mercy. Though speed comes at a price.
"I came here to perform surgery and I don't much care upon who."
Let's imagine it's 1820 and your leg has turned so green people think you're a quarter Hulk. You've taken your whiskey and hear your doctor walk in the door. Then you hear your audience walk in the room, followed by the booming, confident voice of the doctor demanding, "Gentlemen -- time me!" Suddenly, your lifesaving procedure is now performance art for Robert "The Flash" Liston. Which was probably pretty nerve wracking for everyone involved, considering he was known to swing his scalpel a bit this way and that in the heat of the moment. Sure, he was able to amputate a leg in 150 seconds, but he occasionally took the patient's testicles as well. Just cut them right off.