The Smithsonian Institution has cut off all public access to a collection of nude photographs taken of generations of college students, some of whom went on to become leaders in American culture and government.

The pictures at first were taken to study posture. Later they were made by a researcher examining what he believed to be a relationship between body shape and intelligence.

All freshmen here at Yale and at some of the other colleges and universities involved were required to pose in the nude. Among those who were presumably subject to the practice are George Bush and Hillary Rodham Clinton, but it is not known whether their photos ever wound up at the Smithsonian, which, although having made its collection of the pictures available to researchers, has never displayed them.

"There are the rights of the subjects to consider," Ildiko P. DeAngelis, assistant general counsel at the Smithsonian, said today in explaining its decision to seal the entire collection, even to researchers. The pictures will remain off limits, she said, until the Smithsonian completes an investigation of how it acquired them and whether it has rights to them.