Many modern surgical instruments are of exactly the same design as those devised in the 10th century by a Muslim surgeon, Abul Qasim Khalaf ibn al-Abbas al-Zahrawi. His scalpels, bone saws, forceps, fine scissors for eye surgery and many of the 200 instruments he devised are recognisable to a modern surgeon. It was he who discovered that catgut used for internal stitches dissolves away naturally (a discovery he made when his monkey ate his lute strings) and that it can be also used to make medicine capsules. In the 13th century, another Muslim medic named Ibn Nafis described the circulation of the blood, 300 years before William Harvey discovered it. Muslims doctors also invented anaesthetics of opium and alcohol mixes and developed hollow needles to suck cataracts from eyes in a technique still used today.