A concrete saccharine exudation obtained by making transverse incisions in the stems of the trees of Fraxinus Ornus, cultivated in Calabria and Sicily.

Characters. - In stalactiform pieces from one to six inches in length, and one or two inches in width, uneven, porous, and friable, curved on one side, of a yellowish-white colour. Odour faint, resembling honey; taste sweet and honey-like, combined with a slight acridity and bitterness.

Dose. - 60 grains to 1 ounce.

Preparation.

U.S.P.

Dose.

Infusum Sennae Compositum.............................

2 1/2 fl. oz.

B.P

None.

Composition. - It consists principally of mannite or mannitol, a hexahydric alcohol, C6H8(OH)6, together with common sugar and extractive matter. The mannite, which forms from 60 to 80 per cent. of the manna, may be extracted by means of boiling-rectified spirit, from which it will afterwards separate on cooling in colourless, shining crystals. It requires five parts of cold water for its solution, and this does not undergo vinous fermentation in contact with yeast, being thus distinguished from grape-sugar.

Use. - Manna is used as a simple laxative.