"Books and documents are rapidly turning to dust and will eventually be as brittle as this one," said one witness testifying before a House subcommittee on funding for the National Endowment for the Humanities yesterday. As she spoke, she crumpled a blank page from an old book into an ashtray.

"Very dramatic," Rep. Sidney Yates (D-Ill.) responded with a chuckle.

The paper crumbler was one of several humanists from museums, universities, research institutions, and service organizations who testified as outside witnesses before the House Appropriations subcommittee on the interior. They argued that NEH support was crucial for new scholarly and cultural work and for stimulating contributions from the private sector.

Documentary films on black musical composers "are still as scarce as hen's teeth and but for the Humanities Endowment would probably not exist," Elias Blake Jr., president of Clark College in Atlanta, who has made such a film, told Yates, the only member who attended the morning session. "We know, because we tried for other funding sources and were not successful."

Hanna H. Gray, the president of the University of Chicago and a co-chair last year of President Reagan's Task Force on the Arts and the Humanities, called Reagan's proposed reduction in NEH funding the result of "short-sighted policies" which would "exact a heavy cost later." NEH supports university collections, libraries, research institutions, and massive projects like the production of an Encyclopedia of the American Constitution sponsored by Claremont College, she said. "No single university's resources would have been sufficient to undertake the project," Gray said. "NEH seed money made it possible for scholars across the nation to collaborate on a project that will vastly enrich our understanding of our nation's legal and philosophical foundations."

Others testifying included Vartan Gregorian, the president of the New York Public Library, and Willard Boyd, the president of the Field Museum of Natural History in Chicago.