"When I walk through this show," said the Corcoran's Associate Director Jane Livingston, "I feel just like the cat who swallowed the canary." Her pride is justifiable. "Acquisitions Since 1975," now on view at her museum, is an encouraging surprise.

The health of the Corcoran, as its friends have noted, has much improved in recent years. It no longer runs a deficit, charges an admission fee or is oven-hot in summer. This exhibition demonstrates progress of another sort. It shows to what degree the Corcoran, of late, has deepened and expanded its permanent collection.

More than 1,300 works of art -- some of them by masters -- have come to the museum, through purchase or through gift, since 1975. Of those acquisitions, 138 have been placed on view. Their labels, read in sequence, present a kind of honor roll of 200 years of this nation's art.

Gilbert Stuart, Eastman Johnson, Jasper Cropsey, Gaston Lachaise, Max Weber, Georgia O'Keeffe, Stuart Davis, Andrew Wyeth, Joseph Cornell, Moses Soyer, Helen Frankenthaler, Richard Diebenkorn, Willem de Kooning, Philip Guston, Phillip Pearlstein, Joan Mitchell, Robert Rauschenberg, Larry Poons, Robert Motherwell, Sam Francis, Andy Warhol, Roy Lichtenstein and Frank Stella are among the painters represented by objects large or small.

Works of art by Washingtonians -- among them Kenneth Noland, Gene Davis, Tom Downing, Jacob Kainen, Sam Gilliam, Rockne Krebs, Michael Clark, Jim Sundquist, Jennie Lea Knight, Tom Dineen, Martin Puryear, Mitchell Jamieson, Carroll Sockwell, Robin Rose, Jane Dow, Polly Kraft, Manon Cleary and V.V. Rankine -- are also on display, and, despite the competition, hold their own with ease.

A number of these objects were surprisingly inexpensive. In 1975, the gallery spent $500 at Harry Lunn's gallery for an Ansel Adams photograph, "Moonrise, Hernandez," which since has sold for 33 times as much at auction.

In 1976, it paid $4,050 for Howard Mehring's "Frontenac" (1958), one of that color painter's most impressive pictures. Its $18,000 Diebenkorn and its $15,000 Stella were also major bargains. But not all the objects on display were acquired for a song.

"The Belated Kid," a late-19th-century painting in the Barbizon manner by William Morris Hunt, cost $118,000. But it fills a major gap in the Corcoran's collection. The same is true of Martin Johnson Heade's luminist "View of Marshfield." It cost $275,000. It is probably the most beautiful--as well as the most important--painting on display.

The acquisition show, quite rightly, is strongest in those areas where the Corcoran's collection has long been thought most weak. The humorous door painting by William Michael Harnett -- which cost $60,000 and shows a chicken, newly plucked, hanging like a trophy--strengthens the Corcoran's collection of meticulously painted 19th-century still lifes. So do William Mason Brown's "Still Life on a Marble Table Top" from the 1880s and A. Kline's "The Target," another 19th-century eye-fooler that eerily anticipates works by Noland and by Johns. The Brown and the Kline cost $15,000 each.

Another gap in the permanent collection -- early 20th-century modernism -- also has been nicely filled by objects on display. These include works by John Storrs, Manierre Dawson, Oscar Blumner, Arthur B. Carles and a brilliant little portrait done in the Fauve manner by Thomas Hart Benton just after World War I.

There are photographs on view by Lewis Hine, Walker Evans, Robert Frank, Paul Outerbridge and other well-known artists. Twentieth-century photography is one area in which the Corcoran's collection is particularly strong. But the gallery, as Livingston acknowledges, still has a lengthy wish list. It does not yet own a major Copley, still lifes by Raphaelle or Rembrandt Peale, or a classic Harnett, or anything by J.F. Peto, or a Pollock, a major de Kooning, a Franz Kline, a Barnett Newman, or a Clyfford Still.

Many of the important pictures shown--the three Stuarts, for example, the Eastman Johnson and the Cropsey -- came as gifts. The National Endowment for the Arts has also helped the Corcoran. Under its recently discontinued Museum Purchase Plan, the gallery was given $110,000 in matching funds, cash that helped buy its Diebenkorn, Stella, Larry Poons, Mehring, and other paintings here.

Another source of money, which made the current show as impressive as it is, was the gallery's own collection of relatively minor works of European art. Eighty of these were sold at auction in 1979. The proceeds -- $158,700 -- were used to buy the Max Weber, the A. Kline, the Heade, the Storrs, the Dawson, and 15 other American works of art on view. Curators Edward Nygren and Jane Livingston have picked these acquisitions carefully and well. They will remain on view through Jan. 2.