Paragons of their species.

Like anyone operating an X-ray machine, Kyle Luckenbill wants to make sure his patients are in good shape.

Yet his goal is more ambitious than most. He wants them to stay in good shape forever.

The "patients" are fish preserved in alcohol at the Academy of Natural Sciences in Philadelphia, some dating to the early 1800s. Luckenbill, a research and curatorial assistant, is in the midst of X-raying 3,000 valuable "type" specimens - ones that serve as official scientific representatives of their species.

The goal is to facilitate scientific inquiry and preservation at the same time. The digital X-rays can be sent to scientists around the world while the sometimes-fragile originals remain safely on the shelf. Scientists compare the images with new finds, looking at such attributes as the number of vertebrae or the rays in a fish's fins.

The images already are in demand, along with accompanying digital photographs, says John Lundberg, curator of the academy's ichthyology department. One recent recipient was a scientist in Venezuela who is examining X-rays of several small catfish to see if they are new species.

When the academy's Barbara Ceiga saw some of the ghostly images from the project, she came up with yet another use for them: as objets d'art.

Through Aug. 1, several of the X-rays are part of the academy's "Art of Science" exhibit, a rotating display that seeks to capture the beauty of life.

"Science can be beautiful, and art can have a really scientific bent to it," says Ceiga, the academy's exhibits director. "There are so many ways to get interested in science, and sometimes it's through the beauty."

The X-rays are hung on the museum's first floor, right outside the butterfly exhibit. No medical expertise required.

- Tom Avril