Re: How is it possible to freeze an animal and for it to continue living?

Amphibians (terrestrial frogs) are especially well-known for hibernating in 
places where temperatures go below freezing.  Since they are 
"cold-blooded", they have no way to keep their body temperature above the 
temperature of the environment. Yet they do not die.  They use a natural 
antifreeze (glucose) in a high enough concentration in vital organs that no 
ice forms.  This is partly due to dehydration of the cells.  In the wood 
frog more than 60% of the water is lost under freezing conditions, and 
the water remaining in the cells never freezes.  Ice crystals do form in 
the bladder, in the hollow body cavity, and under the skin, so they are 
partially frozen.  During this time they stop breathing and the heart stops 
beating, so the frog appears to be dead.

Many species of fish from the polar regions can also survive sub-freezing 
temperatures.  A protein in their blood has been identified as an 
antifreeze.

Scientists are studying these natural antifreezes to see if the same 
principles can be used to preserve human organs so they can be stored for 
transplantation.

If you have access to "Discover" magazine, see the article "Biology on Ice" 
in the August 1994 issue, starting on p. 36.