Encyclopedia
Beaver Stream
Castoreum is a resinous substance of brown, reddish, or yellowish color with a bitter taste and pungent odor. It is secreted by beavers and produced in skin glands (usually paired), where it is stored. These are skin folds measuring 5 - 10 cm in length
Source: "Explanations to the Commodity Nomenclature of Foreign Economic Activity of the Russian Federation (HS of Russia)" (prepared by the Federal Customs Service of Russia) (volume 1, sections I - VI, groups 1 - 29)