The last nude by Thomas Eakins (1844-1916), that Philadelphia master's final exploration of a subject he had pursued throughout his long career, has been given to the National Museum of American Art. It goes on view today.

"William Rush's Model" is a gift to the museum from R. Crosby Kemper Jr. and Mary Kemper of Kansas City, Mo., who recently acquired it from a New York dealer. R. Crosby Kemper is one of the museum's commissioners. The picture had been owned for many years by Sheldon and Caroline Keck, the well-known art conservators. Though the price the Kempers paid was not announced, the canvas has a current market value in the neighborhood of $500,000.

It recapitulates a set of themes -- the nude perceived in motion, the act of working from live models and the history of art in blue-nosed Philadelphia -- that obsessed the master. Eakins, though no Modernist, could not bear the phoniness of most socially acceptable academic painting. He spent his final years trying to force flesh and blood into a painterly tradition already largely moribund when this 3-by-4-foot canvas was done in 1908.

The picture, void of flattery, might be thought unfinished, for it suggests more than it shows. It depicts a naked artist's model, surrounded by a kind of fog, descending from a pedestal. Her Philadelphia surroundings -- the sculptor who employed her, his hammers, sw,2 sk,2 chisels and the studio where he worked -- are not stated, just implied.

William Rush of Philadelphia (1756-1833), one of Eakins' heroes, was the first artist in America to work directly from the nude. In 1876 -- to celebrate his city, Rush's contributions, America's art history and the U.S. centennial -- Eakins made a giant, though demure, picture of the sculptor in his studio. It showed Rush studying his model while carving his wooden allegorical statue "The Nymph of the Schuylkill."

Eakins' own attempts to follow that example -- the painter taught his students to dispense with plaster casts and paint directly from nude models -- ruined his career. In 1886, Eakins, then director of the Pennsylvania Academy's art school, asked a male model to pose without his loincloth. There were ladies in the classroom, and Eakins lost his job in

The loss of his position was more than a financial disaster; it robbed the portrait painter of his respectability and his local influence. But Eakins would not bend. The naked human body continued to absorb him. Eakins photographed nudes swimming and he dissected corpses. Once he even went riding naked on a

Then, in 1908, as if the memory still galled him, Eakins started painting William Rush again.

That year he completed three far-from-demure versions of the studio scene. Two of them (one is now in Brooklyn, the other in Honolulu) show the sculptor assisting the model from her perch. In the third, the one now here, Rush is but an echo.

But the nude is fully seen. Her flesh is painted with enormous sensuality and uncompromising truth. The brownish background, loosely brushed, forces one to recognize the flatness of the canvas, but the figure is so sculptural it seems to step into the room. The painting, while apparently incomplete, may partially suggest the imminent completion of Eakins' own career. Not long after it was finished, the painter's eyesight failed. He died in 1916.