A boy who was sent to hospital with breathing difficulties stunned doctors when he hacked up the grim cause of his problems - 12cm-long leech. And it was alive. Seven-year-old Xiaoxiang had a ...

In this short film Dr Michael Mosley interviews a surgeon who is pioneering the use of leeches in medical research. He allows a leech to attach to his arm and suck his blood, the mouth of the ...