The first recorded clinical use of medicinal leeches (Hirudo Medicinalis) occured approximately 2500 years ago. Since the leech's bite produces a small bleeding wound that mimics a venous circulation in an area of compromised tissue, this small invertebrate animal is particularly valuable for plastic and reconstructive surgery. The leech produces a number of important substances which contribute to the special property of the bite, including an anticoagulant, and a local vasodilator. These substances allow continued bleeding for up to 48 hours after the animal has been detached.