Most humans contain between nine and twelve pints of blood. Here Rose George, who probably contains nine pints, tells nine different stories about the liquid that sustains us, discovering what it reveals about who we are. In Nepal, she meets girls challenging the taboos surrounding menstruation; in the Canadian prairies, she visits a controversial plasma clinic; in Wales she gets a tour of the UK's only leech farm to learn about the vital role the creatures still play in modern surgery; and in a