The fourth digit or ring finger of the left hand has become the customary place to wear a wedding ring in much of the world, though in certain countries the right hand finger is used. This custom was practically established as the norm during World War II. The use of the fourth finger of the left hand (the 'ring finger') is associated with an old belief that the left hand's ring finger is connected by a vein directly to the heart: the vena amoris or vein of love. This idea was known in 16th and 17th century England, when Henry Swinburne referred to it in his book about marriage. It can be traced back to ancient Rome, when Aulus Gellius cited Appianus as saying the ancient Egyptians had found a fine nerve linking that particular finger to the heart.