As incredible as it sounds, a man was able to grow back his finger, vessels flesh and nail, in only 4 weeks after it was cut off by a model airplane propeller.

Lee Spievack's brother, a medical research scientist, gave him a special powder to sprinkle on the wound, which grew the finger back. The powder is made from pig bladders called extracellular matrix. It is a mix of protein and connective tissue surgeons often use to repair tendons and it holds some of the secrets behind the emerging new science of regenerative medicine.

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