In the shadow-streaked splendor of the first Saturday in May, edging toward twilight's last gleaming, they wait in the gate, snorting like steam engines, dancing impatiently on those matchstick legs, quivering with pent-up energy, muscles bunching and coiling, yearning to be unleashed.

Then the starter sets them free. They come boiling out in bumping, jumbling, altogether glorious chaos, and the drumbeat of their hooves sounds like rolling thunder. And one mile and one quarter later, in no more than two minutes, give or take a blink or two, one of them will have run the fastest of all through that shattering wall of noise down the homestretch, and the little man on the big horse's back will stand up in the stirrups in triumph and lean over and whisper into one of those twitching velvet ears: "You've won it, baby!"

In the winner's circle they will drape a blanket of red roses across those muscular shoulders, and all will smile for the camera. There are richer races. There are longer races. But there are none as famous as this one.

"When people find out what you do," said the jockey Jerry Bailey, "they always ask if you ever won the Kentucky Derby."

Bailey has, and more than most he realizes that the odds against it are discouragingly staggering. For starters, there is only one opportunity per animal per lifetime - the Derby is limited to those 3 years old, no younger, no older.

In 2004 in the U.S. of A., 34,642 thoroughbreds were foaled. Of those, 450 were nominated for the Triple Crown races - Derby, Preakness, Belmont. Tomorrow, for the 133d running, the field will have been winnowed to fewer than two dozen. Even for a sport that gave us the term long shot, these are daunting odds.

In the words of the balladeer Dan Fogelberg: "The chance of a lifetime in a lifetime of chance."

There are no guarantees. The irony is that these magnificent creatures, half a ton and capable of 40 miles an hour, are also fragile, vulnerable, and sometimes easily spooked, given to jumping over shadows. One misstep . . .

Last year, a 2-year-old named The Green Monkey was purchased for $16 million. Nagged by injury, it has yet to run a race. And might never.

For the last three years, the trainer of the year has been Todd Pletcher. He has saddled 14 mounts in Kentucky Derbies. He hasn't won one yet. In this year's Derby, he sends five to the post. We haven't always had the best horse, he said. And even when you do have the best horse, it doesn't always win.

Last year, the Derby was won powerfully, impressively, by a four-legged machine named Barbaro, who almost instantly won a huge following among the public. That following swelled two weeks later when, only a few strides into the Preakness, the colt's right hind leg seemed to come apart in a hideous explosion. There followed more than half a year of frantic attempts to, first, heal Barbaro, and finally, to save him. In the end, neither was possible.

The public outpouring was overwhelming. The colt's every hiccup was chronicled and analyzed. Clearly, Barbaro had tapped into an emotional hole.

The scoffers and hard-hearted ridiculed the mourners, sneered at such maudlin displays. It's a horse.

But, of course, he was much more than that. They all are. The sentimentalists among us are touched by their majesty, their nobility. We respond instinctively to their beauty, the liquid eyes, the nostrils working like a blacksmith's bellows. To stand next to one is to be awed by the power and the grace.

We don't always do well by them. Some of the medication is questionable at best. The racing surfaces ought to be safer, have some forgiving yield to them. The Triple Crown races should be spaced farther apart.

Once, a long time ago, it was called the Sport of Kings. The track was where you went to gamble. Then came the lotteries. Followed by the casinos. Tracks withered and turned into malls.

Now, the circle seems to come full - the trend is to racinos. Slot machines stuffed into tracks, with some of the money funneled into larger purses, the intent alleged to be improved racing. Will it be the salvation of a sport? Or just a distraction?

There is a definition worth remembering - horse sense: the sense horses have not to bet on humans.

Bill Lyon (lyon1964@comcast.net) was an Inquirer sports columnist for 34 years.