Philadelphia — It was a celebration 100 years in the making. It happened downstairs in the sprawling civic center here - beyond the Kal-Kan and Purina concessions, beyond the ''I Love Afghans'' shoelaces, past the porcelain poodle bookends.
It was, quite simply, the largest gathering of man and dog ever assembled in North America.
For two full days last weekend, thousands of America's finest purebred dogs primped and pranced - 141 breeds from 49 states showing off everything from silky coats to soulful temperaments. Scowl-faced judges admonished dog handlers to ''slow down'' and go ''easy on the lead.'' Owners jockeyed their dogs to best advantage - fastidiously propping ears, head, and tails to mirror the pictures in ''The Complete Dog Book.''
Why all the hoopla? Because the American Kennel Club, the producer of that journal of dog-breeding standards and the largest animal registry in the world, has reached its centennial year.
The AKC, established in Philadelphia in 1884, is a nonprofit organization of 438 member clubs. To celebrate its centennial, the AKC brought together 8,075 animals for its most prestigious of shows - the only one of its kind since 1926. Beyond the awarding of ribbons and trophies for ''best of breed,'' ''best of group,'' and ''best of show,'' the gathering was to commemorate man's best friend.
''He's also man's oldest friend, and been found on artifacts going back 15, 000 years to prove it,'' says AKC president William Stifel, sitting in a quiet office overlooking the 26 numbered show rings. ''I'm convinced that if the tables were turned and it were humans that were trying to befriend a higher form of life, we'd be asking a lot more than the dog has ever asked of us.''
The club is dedicated to the development of purebred dogs. ''Dogs from the pound - mutts, mongrels, and mixed breeds - are wonderful and make marvelous pets,'' says Muriel Sonnichsen, a breeder and dog-show judge from Connecticut. ''But if you want to herd or hunt, you'd better have a dog that is purebred for what you're hunting or herding.'' Purebred, she says, means the dog has single-breed heritage through at least eight generations.
For the centennial gathering, the group of 8,000-plus dogs was narrowed to 141 (''best of breed''), then to seven (''best of group''), which included a German shepherd, a golden retriever, a bloodhound, a Doberman, an Irish terrier, a Maltese, and a bichon frise. Those who remained of the weekend's 60,000 spectators crammed into the civic center for the main event: ''best of show.''
After stroking each of the seven from nose to tail, the ''best of show'' judge, William L. Kendrick, watched closely as each trotted around the carpeted arena floor. He scribbled his choice on paper: the German shepherd named Ch. Covy Tucker Hills Manhattan, from Lyndonville, N.Y. The crowd erupted. Cameras flashed.
''It was his lovely, fluid gait, especially in the side view, and a never-failing, excellent demeanor that carried the day for him,'' Mr. Kendrick later told the press.
In a separate interview after the show, Mr. Kendrick said the lay person doesn't have the vaguest idea what separates one dog from the next, good from bad. ''I constantly hear people whispering, 'What's he looking for?' '' says the silver-haired Kendrick. The judge's most important criterion, he says, is watching the dog's movement.
''A dog makes the most of himself when moving, and shows you the structural points that can be hidden when he's standing - withers, shoulders, hocks,'' Kendrick says. Movement also reveals the dog's natural, inbred qualities. ''If a dog is a bad mover, all the training in the world won't help him,'' he says.
Kendrick also says this centennial celebration has reignited an age-old debate within AKC circles over the concept of declaring one breed better than another in the ''best of show.''
''It's a little like trying to decide who's a better athlete, Bjorn Borg or Jack Nicklaus,'' he says. ''And some past (AKC) directors have fought against interbreed judging. But we continue, because Americans must know their winner - the best, top dog.''
Kendrick has been judging dogs since 1926, the same year he garnered an award at the only other national event in AKC's history. He is known as dean of about 20 ''all-arounders'' - that increasingly rare breed of judge qualified to pass judgment on any of 141 breeds now recognized by the club.
''Since it's well-nigh impossible to compare a toy poodle, say, with the enormous Great Dane,'' Kendrick says, ''an all-around judge should have in his mind his conception of the perfect specimen of each breed. Whoever comes closest to that perfect specimen should win.''
Although the standards for each breed are very specific he says the layman should keep in mind three things: character, condition, and demeanor. ''The first is knowing which tails should curl, which are straight, where ears fall, and so on. Second is knowing such things as whether a dog's ribs should show, or whether he's starved. Third is temperament. No matter how good a dog looks, if he pulls away and sulks, he's not going to win anything.''
Breeding for show, as opposed to temperament, is in fact an issue that is raised quite often with AKC officials in this or any other year.
''I would say if you're involved with showing dogs, there may be some exploitation there - if, by getting more points, you can charge more for your litters if you breed,'' says John C. Wright, an associate professor of psychology at Mercer University, who also counsels families on behavior problems in dogs and cats.
''I'm concerned that the emphasis that breeders and dog showers put into their breeding programs can ignore the qualities of dogs as pets for the family and breed only for conformation (to accepted body types).''
But Mr. Stifel and other AKC officials respond that one of the primary motives of the organization is to educate breeders about the dangers of faulty breeding procedures. To do so, the club produces brochures, videotapes, and other educational materials. But no method of enforcing breeding practices exists.
''The situation is especially bad when one breed becomes very popular all of a sudden, creating demand for unknowledgeable breeders to get in on the act,'' Stifel says. He says this happened 20 years ago with poodles, which continued to lead the list of registrations until last year. ''The new leader is cocker spaniels,'' he says. ''And now we're seeing more problems with them as well.''
Asked about recent trends in the dog world, Stifel says that the number of AKC dog registrations a year has remained steady (about 1 million) for the past decade. (The AKC registered its 25-millionth dog in 1981.) The number of dog events has grown slightly, to about 1,000 all-breed shows a year and 1,300 to 1, 400 specialty (one-breed) shows. Including practice events and field trials, the total is nearly 5,000 dog events.
The AKC has opened its decisionmaking processes to more dog owners in recent years. It has also removed the stipulation that voting delegates from member clubs be male. As a result, he says, women have ''brought all the qualities to policy matters they had always brought to judging. And they changed the feeling of the organization from a men's club to just a club - which has made all the difference.''