The only bruises in golf are to the spirit. The only bones that break are those in the skeleton of the personality.The only blood that flows is from a sort of internal hemorrhaging of self-esteem. Golf tests not so much the muscles as those qualities of stable judgment and emotional courage that resides between the ears.

The final round of the Masters, more than any other day in the golfing year, brings this irreducible, unrelenting core of the sport into focus.

The man who is in the lead, on the lead or near the lead at Augusta National on the final day of the first full week in April faces the ultimate punishments, humiliations and pleasures of his game. Whether it's the truth, or the merest jock poppycock, every player here believes that Masters' Sunday is not only a test of his golf but a relentless examination of his soul. These men have worked too long, reached too precise and predictable a level of craft to think they're just knocking a ball at a hole in the ground. That they believe it so earnestly, in a sense, makes it so.

"Golf is the 'only-est' sport," said Hale Irwin, twice U.S. Open champion. "You're completely alone with every conceivable opportunity to defeat yourself. Golf brings out your assets and liabilities as a person. The longer you play, the more certain you are that a man's performance is the outward manifestation of who, in his heart, he really thinks he is."

Much of the public talk at any Masters is of strategy. Players exchange their annual monographs on how to achieve the proper confident attitude, or how to escape the Sirens in the Amen Corner, or, of the necessity to attack (or be attacked by) a course designed to reward boldness and punish timidity.

However, in private moments, they don't talk about the tricky winds that swirl above Rae's Creek nearly as much as they talk about the far more devious winds that blow in their own brains.

"I'm convinced it's all here," said Ben Crenshaw, jabbing his forefingers into his temples. "This course will play with your mind, put you through the wringer with good and bad breaks. There's no way to make 18 consecutive pars here; there's no safe way to play. So, the course throws you back on your emotional resources.

"Look at Jack Nicklaus and you know what the final round at Augusta is all about.I think he has more belief in himself, more supreme confidence, than any golfer ever. He thinks he deserves to win and that he's destined to win. So, he does win. It's written all over him.

"He can channel his concentration and ignore distractions and annoyances better than anybody who's ever lived."

This game and this course, in particular, were created with humiliation in mind. Yet, those who prosper here are those with such stubborn self-regard that they refuse to be humbled.

Two years ago, Graig Stadler erupted in the Amen Corner; on a day when 70 would have netted him a green jacket, he shot 76. Behind the azaleas on the 12th hole, during a delay in play, Stadler sat down and cried. "Most of us are that way . . . I'm that way . . . the game just embarasses you until you feel inadequate and pathetic," commiserated Crenshaw. "You want to cry like a child.

"The two best players I've ever seen at ignoring their own mistakes -- and I'm talkin' about some really ugly shots in big pressure spots -- are Nicklaus and (Tom) Watson. They refuse to be embarrassed. In fact, everybody on tour knows that Nicklaus probably hits more unbelievably terrible, almost amateurish shots, than any great player who ever lived."

"You can talk about strategy all you want, what you do when you're a shot ahead or a shot behind, but what really matters is resiliency," Irwin said. "On the last nine holes of the Masters or the Open, there's going to come at least one point when you want to throw yourself in the nearest trash can and disappear. You know you can't hide. It's like you're walking down the fairway naked. The gallery knows what you've done, every other player knows, and, worst of all, you know. That's when you find out if you're a competitor."

For young, promising players, no gift is more cherished than this mysterious ability to hold the swing, the tempo, the psyche and the soul in one meshed piece when your professional world, your highest dreams, are in peril.

"I watch Nicklaus and I know what his key is. Somehow, he feeds off his own emotion, yet also puts himself beyond it," said Peter Jacobsen, the 26-year-old of whom Arnold Palmer has said, "If there's a future 'Palmer' out here, it's probably Jacobsen."

"I was thinking about it today," Jacobsen said Friday, after his 71-70 -- 141 total had put him in eighth place, and squarely on the leader board, in his first Masters. "As I walked through the Amen Corner I said to myself, "This is the epitome of golf. After all these years, I'm really right here.'

"But, at the same time, I was trying to put myself beyond it. You can't say, 'I'm so excited I'm going to die.' If you get caught up in all the history, and all your own daydreams, you could choke your brains out. Every guy out here has stood on the practice tee for hours and said, 'Okay, this is my drive at the 13th at Augusta . . . gotta draw it around the corner, but not too much. Now, I gotta smoke this one-iron over Rae's Creek and stop it on this slick green.'

"Well, today I did it in real life just like the fantasy. I had a 10-foot putt for eagle at the 13th," said Jacobsen, who won $138,562 and a tournament last sesson but is more famous for his imitations of famous golfers.

"I'm convinced that your subconscious can't tell the difference between reality and dream. So, you have to paint a mental picture of your future in detail. All those six-foot putts are mad back here," he said, patting the back of his head. "You can't do it unless you've imagined it first.

"I could look at my accomplishments and say, 'Jake, you're a midget. You don't belong here.' But I'm sure Nicklaus never said, 'These guys are too good for me.' You can only move to where and what you deep down believe you are.

"I think players have a fear of finding out their true limits which is even greater than their fear of failure," Jacobsen said. "You want an excuse. You want to say, 'Well, I'm not playing well,' or, 'I just took a bad swing.'

"What if I have two more good rounds? What if I come to the 72nd hole Sunday and I have a chance to do something? Am I going to have the guts to stand in there and hit the best shot I can and accept the consequences? All those practice shots don't mean a thing. You have to be able to stand on the last hole and say, 'It's due right now.' And then perform.

"When the great player screws up, he says, 'I'm going to work on that and not do it again,'" Jacobsen said. "The bad player says, 'Boy, I screwed up again. I guess I really am a dog.'"

"To play well on the final holes of a major championship, you need a certain arrogence," Irwin said. "You have to have a way to rise above, or drop below, anxiety. You have to find a trance, some kind of self-hypnosis that's almost a state of grace. Everything that goes wrong crashes against that trance.

"I'm not sure that Nicklaus knew the legitimate taste of victory until last year at the Open Because, in his whole career, he'd never known a lack of success," Irwin said. "I think the rest of us, who have scuffled, had a greater love for what he'd done than he did. I'm not sure he really understood the magnitude of his accomplishment. "That one bad year in '79 was a black mark on Jack's dignity. It hurt his self-esteem. That had never happened. I think that's why he's come back with such a vengence. I don't think he's ever wanted to win as much as he does now because I'm not sure he really knew how good victory tasted since he took it for granted."

Nicklaus' shadow is so long and encompassing, gathering in his whole era, that, whenever his names rises to the top again, the golf world asks. as Shakespeare's Cassius did, "On what meat doth this our Caesar feed that he hath grown so great?"

After all, the history of golf runs counter to Nicklaus' example. Johnny Miller, after finishing bogey-bogey at the '71 Masters to miss a playoff, was asked what happened; I suddenly realized who I was and where I was," he said. Crensahw, when asked why he has never gotten close to winning here, said, "I wish I didn't know so much about this tournament." And Trevor Homer, a British amateur of a previous generation, when told that the Masters odds against him were 500 to 1, said, "It should be 5,000 to 1. For an amateur, standing on the first hole of the Masters is the ultimate laxative."

Nicklaus, of course, going into the final day trailing Tom Watson by a stroke, has no answer to the question, "What gives you the right to be so good?" It's a birthright that he has never questioned. "I'm a golfer," he said. "I like to win. I'm not afraid to dicker with any part of my game at any time.I'm a fiddler. I enjoy working at the things that let you win."

At the technical level, Nicklaus may have his strategies and swing-thoughts. However, that's not what separates him from Hervert Green, who in '78 blew a three-shot Sunday lead, then missed a three-foot putt that would have forced a playoff; or from Ed Sneed, who in '79 squandered a five-shot, last-round lead, finished bogey-bogey-bogey, then disappeared in a playoff.

Part of the difference is in athletic talent, experience, and the like. But, for those who think they can hear golf's heartbeat Sunday afternoon at Augusta, the most essential difference is an indefinable quality in Nicklaus' laser eyes. Perhaps, in part, it is an aura of dignity and self-esteem that refuses to be embarrassed by chance or failure.

Whether Nicklaus gathers a sixth green coat to his crowded golfing closet, or must settle for five, is not the point. As he walks the final holes of this Masters, plucking at his shirt front, disguising behind a genial, practiced smile what is really a fierce trance-like concentration, Nicklaus will be an example of the rarest thing in sport -- a player who epitomizes an entire game.

At that moment, Nicklaus will be a man who, for a few hours, has achieved a perfect state of grace.