The last time Joe Frazier put his unprotected nose in front of someone's fists, George Foreman dropped a five megaton bomb on it. Even now, when George is retired and preaching the Lord's word, fighters speak of his strength in hushed awe. So a soft-nosed reporter, wondering what it feels like to be knocked out in the ring, asked Joe Frazier about the Foreman fight.

"Er, uh, Joe . . . " the reporter began boldly. The idea was to find out if Tommy Hearns can knock out Ray Leonard in their championship fight here Wednesday. Is there such a thing as an iron jaw? A china chin? If a fighter gets hit solidly, how does he stay upright? Or, as in Frazier's case with Foreman, why does a fellow get up five times to get knocked down again?

"Joe, when George hit you good . . . " the reporter ventured, not knowing if Frazier would appreciate this line of questioning, which is, truth be told, like asking the Titanic's captain his feelings about icebergs.

"Ali hit me a thousand times," Frazier said. He was smiling, praise be. "Ali never hurt me. But George, now he could hit."

"What'd it feel like?"

"Like this," Frazier said.

He hummed. Frazier pressed his arms against his sides, as if petrified, and then he hummed, a tuning fork struck with a sledgehammer.

"Hmmmmmmmm," the old champion hummed. "It sounds like one big solid bell. A bell nobody can hear but you."

"Why did you keep getting up?"

" 'Cause they pay me to fight," Joe Frazier said, "not lay down."

The knockout is a concussion of the brain. The blow rattles the brain against the skull. The brain is bruised. To save itself from more damage, the brain shuts down.

Ferdie Pacheco calls it a short circuit. Pacheco, a doctor who worked a dozen years in Muhammad Ali's corner, said: "If I hit your arm, you'll get a welt there. The skin expands. It's the same thing with the brain. It's floating in fluid inside your skull, and if you knock it against the bone, the brain is bruised. It swells up. This expansion cuts off the nerve impulses. You're knocked out."

The brain's defense mechanism is so effective, Pacheco said, that men knocked out don't remember what caused it.

"I went to pick up one of my fighters, and I asked him: 'Do you know where you are?' " Pacheco said. "He said, 'Yeah, somewhere close to here.' "

Why did Floyd Patterson's chin give off the clear ring of fine crystal and yet George Chuvalo, to name a rock, couldn't be knocked out by an Amtrak locomotive?

"That's never been found out, why some guys can take a punch and others can't," Pacheco said.

Jimmy Jacobs disagrees. A fighter's manager, Jacobs is a student of the game, for 25 years a collector of classic fight films.

"The idea of 'Does he have a good jaw or doesn't he?' is a myth perpetuated by people who don't know that it is a fighter's attitude, not his chin, that determines who will be knocked out," Jacobs said.

"Fighters that don't want to get knocked out -- Rocky Marciano, Muhammad Ali, Sugar Ray Robinson -- don't get knocked out. There is a great correlation between attitude and survival. I just don't believe that nature wires the jaw to the brain differently in different men.

"Ali is the perfect example. When he had absolutely nothing left to fight with, against Larry Holmes for instance, he still refused to be knocked out."

Scott LeDoux won't quit, either. He is a journeyman heavyweight who was here this morning because he may fight Frazier if, heaven help us, Frazier is serious about coming back.

A charming fellow who tends bar at "LeDoux's Corner" in Dayton, Minn., LeDoux said he remembers one thing about Foreman's punches that caused a referee to stop their fight.

He didn't remember how they felt.

"I remember the sound," LeDoux said.

He went, "BOOOOOOMMM."

Mike Weaver couldn't hurt him if he hit him with the corner stool, LeDoux said, but Duane Bobick once caught him with a left hook he didn't see. He didn't even know he'd been hit until he heard the referee saying: " . . . four."

"I asked the ref: 'What in the hell happened to one, two, three?' I got up right away, and he knocked me back down. This time I was all right, but the ref stopped it."

Before the Foreman fight, his trainer advised LeDoux: "If George happens to knock you down, don't jump right up."

"So he knocks me down," LeDoux said, "and I'm down there -- 'One, two' -- and I'm listening and thinking, 'Should I start getting up now?' 'Three, four.' 'Maybe now.' Hell, I started to get up and found out I couldn't. I got up at 9 1/2."

The referee stopped it anyway.

"I asked him: 'Why you stop it?' " LeDoux said. "He said: 'You're cut real bad under your eye.' I looked at the floor and there was a big pool of blood. I said: 'That's mine? Okay.' "

As LeDoux came down on the side of discretion, Max Baer 46 years ago saw no need to argue against the inevitable.

"I looked across the ring," Baer said of the night he fought Joe Louis, "and realized I wanted to go home early."

Louis, by a knockout, fourth round.