Leeches are hermaphroditic and hematophagous annelids. One important medical species, Hirudo medicinalis, comes from hirudiniculture of fresh water pools. Thanks to their three mandibles with some 300 teeth on their anterior muscular sucker, they easily grab to tissues and by secreting their saliva containing numerous powerful enzymes, such as hyaluronidase, collagenase and inhibitors of platelet aggregation and coagulation, like hirudin, allow blood sucking. Once they are full of blood (up to 15 g of blood), they detach themselves from their prey. Used ever since the 18th Egyptian Dynasty, leeches became famous during the first part of the XIXth century, thanks to a French physician, François Joseph Victor Broussais, known to his adversaries as the "vampire of medicine" for treating various conditions such as phlebotomy, laryngitis, ocular problems, obesity, mental disorders, etc. Overfishing, therapeutic failures and most particularly, the emergence of hygiene, brought the decline of living leeches. In 1884, an extract of leeches was obtained--hirudin and henceforth used. Nowadays, leeches are still used in microsurgery to enhance the venous circulation in finger reimplantation or skin flap transposition. Hirudin is synthesized through recombinant DNA technology and molecules such as lepirudin and desirudin are available on the market as anticoagulant.