This is the way a wood frog freezes:
First, as the temperature drops below 32 degrees, ice crystals start to form just beneath the frog's skin. The normally pliant and slimy amphibian becomes -- for lack of a better word -- slushy.
Then, if the mercury continues to fall, ice races inward through the frog's arteries and veins. Its heart and brain stop working, and its eyes freeze to a ghostly white.
"Imagine an ice cube. Paint it green," and you've got the wood frog in winter, said Ken Storey, a professor at Carleton University in Ontario. The frog is solid to the touch and makes a mini-thud when dropped.
But it is not dead. When a thaw comes, the frog is able to melt back into its normal state over a period of several hours, restart its heart and hop away, unscathed.
This amazing process of reanimation -- repeated every winter in the woods of Maryland, Virginia and the District -- is being examined by scientists hoping to learn the secrets of the frog and other animals that freeze solid.
The hope is that these apparent Lazarus routines can yield clues for improving human medicine, including better preservation of organs on their way to transplant patients.
"Here's an amphibian that has solved the problem of cryo-preserving its organs -- all of them, simultaneously," said Jon Costanzo, a professor of zoology at Miami University in Ohio. "And we haven't been able to do that with one [human organ]."
The Washington region is actually home to several species of what scientists call "freeze-tolerant" animals. One is the wood frog, a two-inch-long creature with a call like a quack, which lives in woods from Georgia to Alaska.
Other local species -- spring peeper and the gray tree frog, as well as a few kinds of caterpillars and the babies of the painted turtle -- can freeze but lose the ability as they age.
Scientists say these animals' freezing abilities are just extreme reactions to a problem that all mid-Atlantic animals face: periodic blasts of winter cold. Human retirees head to Florida, Chesapeake Bay crabs bury themselves in the mud and most frog species hide out deep underground or underwater.
But not the freezing frogs. Instead, buried just a few inches under dirt and leaves, they welcome the chill. When the soil starts freezing -- even if it falls just a couple of degrees below 32 -- so do the frogs.
The result is something like the frozen gray tree frog that Professor Jack R. Layne Jr. held in his hand this week in a lab at Slippery Rock University in Pennsylvania.
Instead of its normal grayish-green, the frog had turned almost purple, its limbs and head stuck in contortions. It looked for all the world like a practical joke: an ice cube made to resemble a frog.