Regenerating amputated limbs is a natural thing for salamanders, starfish, crabs, and lizards, but not humans, nor for frogs under normal circumstances. For humans, growing a new limb is a dream, although we can regenerate skin and liver tissue. Research into this area takes us to an animal a step above salamanders. Scientists at Tufts University have been able to spur growth of a new leg on several adult African clawed frogs.
The frogs' freshly-amputated leg stumps were covered with a silicone cap containing a cocktail of five drugs. Some of these drugs inhibited the creation of scar tissue over the wound, while others stimulated bone, tissue, and nerve growth. The drugs were administered for just 24 hours, and the limb regrowth occurred over the next 18 months. The new limbs were not perfect, as the bone didn't extend into the toes, but the frogs could use them to swim.
The research team hopes to use this technique on other animals, including mammals. Read about this experiment at Tufts University. -via Real Clear Science