Five fingers, five toes. There's nothing magical about the number, yet five digits at the end of their limbs is a motif that runs through all the animals with four limbs, called tetrapods.

On my weekly visit to a research laboratory, I encountered a 14-month-old dog with lameness in its left hind limb. The dog is ... the Care and Use of Laboratory Animals. The facility has a diverse ...

Bone can heal itself, but not always in the ways we expect. Some animals regrow entire limbs. Others, like humans, can only ...