Animals provided with suckers surrounding the mouth, and living a semi-parasitic life, their food being mainly derived from the blood of other animals. They extract blood by means of the sucker, which has several large, sharp teeth. Land leeches live in tropical forests and can attach themselves to a person's ankles and lower legs. Aquatic leeches are found in warm water and may attach themselves to swimmers. Their bites are painless, their saliva reducing the clotting properties of blood with hirudin, the result being that the wound continues to bleed after the leech has detached itself or been gently removed (lighted match, alcohol, salt, and vinegar are all effective removal agents). The medicinal leech, Hirudo medicinalis, was formerly employed for the removal of small quantities of blood in inflammatory and other conditions. Nowadays it is occasionally used to drain haematomas (see HAEMATOMA) and to manage healing after certain types of plastic surgery.