<P> In addition to its usual purpose as an edible leafy vegetable, lettuce has had a number of uses in ancient (and even some more modern) times as a medicinal herb and religious symbol . For example, ancient Egyptians thought lettuce to be a symbol of sexual prowess and a promoter of love and childbearing in women . The Romans likewise claimed that it increased sexual potency . In contrast, the ancient Greeks connected the plant with male impotency, and served it during funerals (probably due to its role in the myth of Adonis' death), and British women in the 19th century believed it would cause infertility and sterility . Lettuce has mild narcotic properties; it was called "sleepwort" by the Anglo - Saxons because of this attribute, although the cultivated L. sativa has lower levels of the narcotic than its wild cousins . This narcotic effect is a property of two sesquiterpene lactones which are found in the white liquid (latex) in the stems of lettuce, called lactucarium or "lettuce opium". </P> <P> Lettuce is also eaten as part of the Jewish Passover Seder, where it is considered the optimal choice for use as the bitter herb, which is eaten together with the matzah . </P> <P> Some American settlers claimed that smallpox could be prevented through the ingestion of lettuce, and an Iranian belief suggested consumption of the seeds when afflicted with typhoid . Folk medicine has also claimed it as a treatment for pain, rheumatism, tension and nervousness, coughs and insanity; scientific evidence of these benefits in humans has not been found . The religious ties of lettuce continue into the present day among the Yazidi people of northern Iraq, who have a religious prohibition against eating the plant . </P>

How many sandwiches can a head of lettuce make