Fragments of Egyptian papyri, found at Kahun in El Faiyum in 1889, are the oldest medical literature that has come down to us from antiquity. They reveal that upper class Egyptian women of the Twelfth Dynasty, about 1850 B.C., used crocodile dung as a pessary, irrigated the vagina with honey and natron (native sesquicarbonate of soda), and inserted a gum-like substance in the vagina. Though elephant's dung was later substituted for that of the crocodile, a similar prescription was used in various places for some three thousand years. It is likely that the contraceptive measures had some effect. Honey and gum would clog the motile sperm; and crocodile's dung, slightly alkaline, would not be much different from a spermicide carried in a sponge. The Ebers papyrus (about 1550 B.C.) contained a prescription for the use of lint tampons moistened with juice from fermented tips of acacia shrubs, i.e. lactic acid.