“The colour should be greenish (like duckweed), and there should be two longitudinal lines having the colour of orpiment and ruddy; they should be rounded and liver-coloured. One may accept leeches which look like little locusts, or like mousetails, with very small heads. But do not accept those with red bellies and green backs, especially if they were collected from running waters.” ~ Avicenna on Leeches, from “The Canon of Medicine”
Leeches have been used for therapeutic purposes for millennia. The earliest traces of the use of leeches appear to date back to 1600-1300 BC to a Greek named Nicander of Colophon. The medical use of leeches is discussed by Avicenna ( Ibn Sina) in The Canon of Medicine (follow this link for the Online Edition of The Canon of Medicine and the section on leeches), as well as by Abd-el-latif al-Baghdadi in the 12th century.