kkleiner writes: "British researchers successfully restored the ability to walk in paralyzed dogs. Special cells taken from the dogs’ noses and transplanted to injured areas caused regrowth of neurons. Within six months the dogs amazingly regained used of their hind legs and were able to use a treadmill, some without a harness. The researchers hope the procedure might one day lead to a cure for humans with spinal cord injury."
We warn the reader in advance that the proof presented here depends on a
clever but highly unmotivated trick.
-- Howard Anton, "Elementary Linear Algebra"