What has thirty-two brains and three jaws, each with one hundred teeth? The correct answer is a leech, and although I hope to never meet one personally, the fact is that they’re still used in medicine today. Bloodletting went out with the nineteenth century, but in the 1980s, with the development of microsurgery, leeches made a comeback. You see, reconstructive surgery, done to reattach limbs or to transfer tissue from one part of the body to another, also involves replumbing the blood vessels that nourish the repositioned tissue or bone.