The amazing 'pixie dust' made from pigs bladder that regrew a severed finger in FOUR weeks
Sponges can do it and so can starfish. For flatworms it is no problem, and both lizards and salamanders can pull off the same trick.
The trick in question is regeneration, the almost magical property possessed by some animals to regrow whole limbs, tails, other body parts or organs if they are lost in an accident.
This spontaneous regeneration has only recently begun to be understood and it involves an incredibly complex interplay of genes and tissues.
What is known is that regeneration does not - except to a very limited degree - occur in humans or, indeed, in any mammals. Cut off a man's leg or a rabbit's foot and the best you can hope for is a scar covered stump.
Cut off a finger-tip and, unless you find a surgeon to sew it back on again promptly, you will simply have to put up with one digit shorter than the rest.
That is, if reports are to be believed, unless you are Lee Spievack, a model aircraft enthusiast from Cincinnati in the U.S. who, in 2005, accidentally sliced an inch off the tip of his index finger with a model aeroplane propeller.
He was offered a tissue graft but refused when his brother Alan, a physician who has been researching tissue regeneration, persuaded him to sprinkle what is being termed "pixie dust" on the stump.
The dust, actually a collagen powder derived from pigs' bladders, appeared to provide a suitable "matrix" or framework, stimulating regrowth of the tissues and division of the cells, to enable Mr Spievack's finger to grow back - in just a month.
And not just a stump - flesh, tendon, skin, fingernail, fingerprints and all.
It is an extraordinary story because, if it can be confirmed, it will point the way to a breakthrough in one of medical science's greatest problems: the inability of humans to regenerate lost tissue.