When Spectacular Bid made his triumphant return to Maryland afterwinning the Kentucky Derby, he was accompanied by trainer Bud Delp and verterinarian Alex Harthill.

Delp justifiably was basking in glory, having captured the most coveted prize of his profession. Harthill, however, had accomplished something unique: Spectacular Bid was the 14th Derby winner in 31 years with which he had been associated professionally.

That statistic merely confirms what many horsemen have come to believe from firsthand experience: Harthill is the best race-track veterinarian in America.

"Doc Harthill is a great vet and a good friend," Delp said. "I asked him to fly to Baltimore with the horse-just in case-because I didn't tranquilize Spectacular Bid. I don't think Doc will be here for the Preakness, but if I needed him I'd call on him."

If Delp did have to call on Harthill, however, the veterinarian would have to come to Pimlico in the capacity ofan unofficial adviser, because Maryland (like most states) will not grant him a license to practice.

At many tracks he is not even allowed in the stable area. Harthill is persona non grata because his career has been marked by controversy as much as by his own professional brilliance.

Harthill was born into his profession. His grandfather emigrated from Scotland to this country in 1872 and set up a veterinary practice in Kentucky. His father, too, treated many Derby horses.

So when Alex graduated from Ohio Statehs veterinary school in 1948, he already had a reputation. There are not many vets, one month out of school, who get to take care of a Triple Crown winner, as Harthill did with Citation.

In 1954, a horse named Mr. Black won a race at Washington Park in Illinois and the postrace urinalysis came up positive for amphetamine. Harthill, the horse's veterinarian, was suspended for 60 days.

The next year he was operating at the Fair Grounds in New Orleans, where he allegedly tried to bribe personnel who conducted the postrace tests for illegal drugs. Arrested by the Louisiana state police on a charge of bribery of public officials, his trial ended in a hung jury.

These blemishes on his record did not lessen the demand for his services at Derby time. It was common knowledge that a trainer who had a horse with physical problems ought to see Doc Harthill. One of the first things serious students of the Derby wanted to know each year was the identity of the "Harthill horses."

Five of them won a Derby during the 1960s, but the last of these triggered headlines across the country that screamed "Kentucky Derby Winner Drugged." Dancer's Image, disqualified as the winner of the 1968 Derby because the painkiller Butazolidin (then illegal) appeared in his urinalysis, was a Harthill horse.

That incident sent Harthill's fortunes into a temporary decline. In 1976 U.S. Customs officers arrested Harthill for trying to smuggle an illegal drug into the country from Canada. Harthill pleaded no contest and paid a fine.

While he obviously possesses a great deal of power, the secret of Harthill's resiliency is still his enormous talent, and the respect he has from the most knowledgeable trainers in the country.

When Ruffian broke down, Frank Whiteley wanted Harthill. When Affirmed launched his Triple Crown campaign, Laz Barrera wanted Harthill. And if Bud Delp ever needs serious veterinary help for Spectacular Bid, he understandably will want Harthill, too.