Blood is the vital fluid which circulates around the body, pumped by the heart. Blood is often used as a thickening agent in cooking, as in black pudding (US: blood sausage). It should not be boiled as it will clot but, on the other hand, this can be prevented by the addition of a little vinegar. It is also used in dishes like jugged hare or civet and coq au vin. In some cultures blood is drunk fresh.