part ii. Materia Medica. — Fraxinus Ormis (Manna). 307

flaky manna, manna in cannoli. The collecting begins aboutthe middle of June, and terminates in September. ■

Manna is brought to Great Britain packed in chests. Thedifferent sorts are in separate packages, and are known by thenames of Flake manna, Sicilian manna, and Calabrian manna.The best is " in oblong pieces or flakes, moderately dry,friable, light, of a whitish or pale yellow colour, and in somedegree transparent: the inferior kinds are moist, unctuous, andbrown."" Manna is said to be occasionally counterfeited by acomposition of honey or sugar, mixed with scammony or someother purgative 3 : but such frauds are now seldom attempted ;and bad or counterfeit manna may be easily discovered by itscolour, weight, transparency, and taste; which are differentfrom those of real manna.

Qualities. — Manna has a slight peculiar odour, and a sweettaste, with some degree of bitterness, not very pleasant, andleaving a nauseous impression on the tongue. The finerpieces, which are often hollow, when broken and examined bythe microscope, exhibit bundles of long beautiful spicularcrystals: but the general texture of the pieces is granular. Itis entirely soluble in water and alcohol; and the latter, whenthe solution has been assisted by heat, deposits on cooling five-eighths of the manna beautifully crystallized; and which maybe regarded as pure manna, and an uncrystallizable mucilagi-nous extractive matter remains, on which probably the pur-gative quality of the drug depends. Fourcroy and Vauquelinsuppose that the common manna of the shops contains fourdifferent ingredients. 1. Pure manna, constituting three-fourths of the whole. 2. A little common sugar. 3. A yellownauseous-smelling substance, to which its purgative qualitiesseem owing : and, 4. Mucilage.

Medical properties and uses. — Manna is a very gentle laxa-tive. It was extravagantly commended by some of the olderphysicians; but is now more justly regarded as a laxative fit forchildren only, and persons of very weak habits. When givenin a dose sufficient for an adult, it is apt to occasion flatulenceand griping; and therefore it is seldom used, except as anadjunct to senna, rhubarb, or solutions of neutral salts, withthe view of covering their tastes.

The dose for children is from 3J. to jiv. ; and for "adultsfrom 3j. to ^ij.

Officinal preparations. Confectio Sennce, L. E. D. Enema Ca-tharticum, I). EnemaJixtidum, D. Syrupus Sennce, D.

FUCUS. Genera Plant. Sckreber.CI. 24. Ord. 3. Cryptogamia Algae. Nat. ord. Algae.

1 Arctuarius is the first Greek who notices manna. Freind's Hist, of Med. i. 271.i I.euis. 5 Alstons Mat. Med. ii. 472.