Cetraria -Iceland Moss.-The entire lichen, Cetraria islandica. Native of the north of Europe.

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

Composition.-Cetraria contains 10 per cent. of starch; 20 per cent. of lichenin, C6H10O5, a starch-like powder, not striking blue with iodine; and two bitter acids-cetraric acid, C17H16O3, and lichenstearic acid, C14H14O3.

Preparation. Decoctum Cetrariae.-1 to 20. Dose, 1 to 2 fl.oz.

Action And Uses

Iceland moss is at once a bitter tonic and nutritive substance, but is not in general use as either.

Litmus.-A blue pigment prepared from various species of Roccella.

Characters.-Small blue lumps, readily reduced to powder.

Preparations.

1. Tincture Of Litmus

Tincture Of Litmus. 1 in 10.

2. Blue Litmus Paper.

3. Red Litmus Paper. _______

Use

Litmus is employed only in chemical testing.

Cerevisiae Fermentum- Beer Yeast.-The ferment obtained in brewing beer.

Characters.-Viscid, semi-fluid, frothy, exhibiting under the microscope numerous round or oval confervoid cells. Dose.-One to two table-spoonfuls.

Preparation.

Cataplasma Fermenti.-Yeast Poultice. Yeast, 6; Flour, 14; Water (at 1008), 6. The mass to be placed near the fire till it rises. _______

Action And Uses

Yeast poultice is believed to act as a sedative and antiseptic, and was formerly applied to sloughing sores, ulcers, and boils. Its value is very questionable.

Yeast has also been given internally on theoretical grounds in zymotic diseases and in diabetes, but probably without success.