Castoreum

Castoreum (from Gk. castor, beaver), the name given to a secretion supplied by both male and female beavers. This secretion - brown, and having a peculiar odour - is contained in two glands or sacs, and among the Hudson Bay traders 10 pairs of these sacs were equal in value to one skin. Formerly castoreum was much used in medicine, and Bacon in his Essay of Friendship recommends "castoreum for the brain." The substance is still used as a perfume.