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. This leech is known for its ability to attach to the skin of various animals, including humans, to feed on blood. In modern medicine, Hirudo medicinalis is utilized in certain therapeutic practices, particularly in reconstructive surgery and to promote blood circulation. The leech's saliva contains anticoagulants, which help prevent blood clotting and can aid in healing by improving blood flow to affected areas.