"Take a good look at all of this, dears," was the advice of one who has spent many years taking good looks at such affairs, "you're watching the end of an era. This is all passing."

"This" was one of the five glittery social events proceding this week's Washington Internation Horse Show at the Capital Centre. The cost of living will soon bring an end to the big, beautiful parties given for the beautiful people, she predicted.

But, from all evidence, the death knell was premature. The glittery social gala was alive and well, even thriving, in Washington as the horse show crowd breezed into town for the annual rites that mark the passage of yet another season.

Wednesday, they gathered at the home of OAS Secretary General Alejandro Orfila. Thursday, it was on to the Four Seasons Hotel for a dinner dance. Friday, a reception was held at the Canadian Embassy; Saturday, it was the Swiss Embassy's turn. On Sunday, they regrouped at the Fairfax Hotel for brunch before they moved on to the opening of the show itself.

Take a good look at this, and judge for yourself.

"You'll see that his gets to be like a sorority or fraternity weekend as the time goes on," retired telephone executive Harold Fangboner said at Thursday's dinner dance. "Everybody knows each other and they keep bumping into each other all week long. All partying together."

"I think of it more as a long house party," was public relations executive Judy Lewis' evaluation. "You keep seeing all the same people and you get dressed up every night."

Martha Reed, who used to ride but now confines her athletic activities to croquet, had flown in from New York for the week. I go to the show at the Garden, but the social events in Washington are always much more exciting for me."

But not for stockbroker William Cook. He had just come in from Aspen for the first reception at Orfila's "We were all nude in the Jacuzzi just last night . . . Washington is so boring after Aspen," he was saying to her.

Reed recently returned to the United States and was concerned about her dog, which was suffering culture shock. "In France nobody minds if your pet goes everywhere, but in this country they have so many rules. She feels so neglected when we come back to New York. Sometimes I just take her with me anyway. I put a Vitton scarf over her and nobody knows she's there when I go into restaurants." Roundup Time

"The horse show is very important to Washington," said gala chairman Margaret Hodges, who is working on it this year for the first time. "I'm doing my best to make money for charity." Money raised at the parties ( $175 per person for all events except Thursday's dinner dance, which cost $100 apiece) will support the show, which in turn will support Girl Scouts, Person-to-Person sporting events, Muscular Dystrophy and the Heart Association.

"It will go on," the chairman maintained, "inflation, recession, it won't matter. There will always be need for charity money to help poor people and good causes." And if this year's response is any indication, there is an abundance of people around who will buy tickets to such events -- every one of the five galas was oversubscribed soon after the invitations were issued.

Contrarily, the horse show itself has never attracted capacity crowds since the move from the Armory to the Capital Centre in 1975. (A Metro stop now occupies the space once used for stabling facilities at the Armory.) Rental costs are higher at the Centre and some of the organizers maintain that it is harder to attract what they consider their largest natural constituency, from the Middleburg area, to Landover.

"Entrance and stabling fees cover all our expenses except the rental of Captial Centre," said True Davis, horse show president. "Our gate covers part of the rent, but we have to rely [on the high-priced social events] to fill in the rest," But even at more than $100 a head, it's not been good enough -- last year the show ended in the red.

One of several innovations this year was Sunday's opening "Western Night," complete with rodeo. Appatently the gimmick worked. According to Davis, it was "the biggest opening night in history." But, there have been some rifts within the committee itself -- six members resigned earlier this year.

Among those members remaining, there is still ambivalence about the changes. Most would like it both ways. Said one: "Sure, I think we should plan an exciting show with lots of appeal to many people, but I don't think we should downplay the social events. That has a glamor and appeal, too. I think people in the audience like to catch a glimpse of some celebrity who is all dressed up for one of the aftershow parties." Sport of Queens

The crowd at the Canadian Embassy on Friday drifted through the entrance hall where Carrie, the ambassador's roly-poly Siamese cat, lolled on the thick green and cream carpet, fixing all newcomers with an icy clue-eyed appraisal, very self-contained.

The guests moved on to the dining room to the left of the hall or to the living and sun rooms to the right, breaking into small clutches that grouped and regrouped as the crowd grew and old friends were spotted. All was fluid movement.

In the far corner of the living room, in perfect counterpoint to the cooly unconcerned feline in the hall sat one straight, stationary figure clad in shades of purple. Mary Elizabeth Tippett is always straight. Mary Elizabeth Tippett is always clad in shades of purple. As the crowd swirled and flowed from room to room, many made a detour past the elegant French antique love seat where she sat. Old friends greeted her as Liz. Everyone knows her as Liz Whitney.

Introduced as having once been married to Jock Whitney, she scoffed, "I don't know why anyone would bring that up. It was so long ago, who would remember?" The 73-year-old, four-times-married dowager empress of the horse world, the woman the Russians call "Mrs Horse," dressed as always in her racing colors of purple and fuchsia sat and expounded on her four-in-hand team that has beaten Prince Philip twice at Windsor.

She will be driving that same four-in-hand this year at the show. She recalled last year when she drove her team to the White House for some pre-show publicity.

"They had the dogs come up to see if the horses had bombs planted on them or something. They sniffed all over the horses and they sniffed me until I finally told them that they had better call them away from the horses' heels unless they wanted them to land in the Potomac."

The dogs were called off. It's hard to imagine anyone disobeying one of Tippett's commands, even the White House security force. Party Game

A little before 6:30, Swiss Ambassador Raymond Probst was worried that no one might come to his, the fourth of the five pre-horse show receptions.

It was Saturday night, the weather had been beautiful -- not promising signs for a Washington party. He needn't have worried. They came in droves, and it wasn't long before the Probst was right there in the middle of it all, enjoying himself and his guests immensely.

At one point, a circle formed as Tandy Dickinson demonstrated a party game wherein both feet are planted side by side and one's cocktail glass is placed next to one ankle. The object is to pick up the glass without spilling the liquid by bringing the hand on the opposide side around behinds one's back and inching down, always keeping the feet together and bending only the knees. Dickinson did it with aplomb. Then she was swept off in a limousine hired by the Aspen crowd. Horseman's Honeymoon

Probst was ebullient as he greeted his guests. This is the first year that a Swiss team has been invited to the international competition in the United States. There is a tradition of dressage riding in Switzerland and the Swiss have done very well in that area in the past, winning more than their share of Olympic gold for the event, but they have never been strong in stadium jumping. This year, they have a team that has done exceptionally well on the European summer circuit, and Probst, one of their strongest boosters, is justifiably proud.

He had invited the team members to the reception. "Normally, when we have competed in other countries," said team captain Rolf Munger, "we never see the ambassador, but this time we received a letter that the ambassador would be happy to see us. We were very honored and we are honored to be here."

The star of the Swiss team is 24-year-old Walter Gabathuler. Earlier this year he won the Prix de Rome. Probst offered a story:

"You know Gabathuler, he is the best of the Swiss jumpers," he said. "He just married the girl who takes care of his horse. I asked him if he brought her here because it would be a good honeymoon. He said she was here, but that she was back at the stable. He said she has two concerns: her husband and the horses -- tonight the horses are first. Later it will be the honeymoon." Enough to Feed a Horse

"Have you ever seen such a variety of food?" said one guest to his compansion at the Canadian Embassy Friday. Platters of shrimp, meatballs, minature quiche, miniature pizza, chicken, barbecued ribs and canapes were being circulated among the guests.

The three embassies seemed to be in an unoffical contest to provide the largest platters and the greatest variety of food. The two restaurants that contributed to the marathon eating and drinking socials were not far behind. It became a concern for some of the partygoers.

Mary Mead, who teaches at Hunter College in New York, eagerly offered a consumer's report for those who were interested in antidotes: "The Golden Door is like boot camp; the Greenhouse is much more relaxing; Main Chance is somewhere in between."

Another guest pooh-poohed the whole notion of fat farms, maintaining that self-discipline was what counted. She had lost two pound over three nights of partying. Besides, "Romania is the only place to go. It's those injections that help. They're the only thing. And they give you a beautiful head of hair." And Still More Parties

"Well it's down to the homestretch now," said Margaret Wimsatt, gala vice chairman. "How is everybody holding up?" Everybody who had crushed into the Fairfax Hotel lounge for mimosas, martinis and Bloody Marys at Sunday's brunch seemed to be holding up very well, indeed. The long dresses, feathers and evening jewels had been shed for more casual suits and hats and the guests looked as fresh as they had at the first reception.

Isn't this an elegant crowd?" said Helena Gray, who, along with her husband, James, U.S.N. (ret.), had been in on every one of the parties. "I don't know how these people do it," she continued, and then remembered that she, too, was doing it. "Usually, five parties would seem just too much, but these have all been so much fun that I have looked forward to all of them."

And there would be more. Over the eight nights of the show, six large receptions are scheduled at the Captial Centre.