The entire lichen, Cetraria islandica. North of Europe.

Characters. - Foliaceous, lobed, crisp, cartilaginous, brownish-white, paler beneath; taste bitter and mucilaginous. A strong decoction gelatinises on cooling.

Composition. - Lichenin and cetrarin or cetraric acid. The former constitutes 70 per cent. of the moss. It swells in cold, and dissolves in hot water, gelatinising on cooling. The latter, which is the bitter principle, is obtained in white acicular crystals, and forms soluble salts with alkalis.

Preparations.

B.P.

Dose.

Decoctum Cetrariae................................

(1 oz. to 1 pint)............

1-2 fl. oz.

U.S.P.

Decoctum Cetrariae .................................

..............................................

2-4 fl. oz.

Action and Uses. - It is demulcent, nutritious, and slightly tonic.