Hirudo medicinalis, commonly known as the medicinal leech, is a species of leech that has been used in medicine for centuries. It is primarily found in freshwater environments across Europe and parts of Asia. These leeches are known for their ability to attach to the skin of animals and humans, where they feed on blood. Medicinal leeches are utilized in modern medicine for their therapeutic properties, particularly in reconstructive surgery and blood circulation improvement. They secrete saliva containing anticoagulants, which help prevent blood clotting and promote healing. This makes them valuable in certain medical treatments.