Manna (U. S. P.)—Manna.
The concrete, saccharine exudation of Fraxinus Ornus, Linné (Ornus europaea, Persoon).
COMMON NAME: Manna.
ILLUSTRATION: Bentley and Trimen, Med. Plants, 170.
Botanical Source.—The manna tree, or Flowering ash, is a small tree, usually 20 or 30 feet high, with a close, round head; the bark is smooth and grayish. The leaves are opposite, unequally pinnated in 3 or 4 pairs; the petioles furrowed; the leaflets petiolate, oblong, acute, serrated, and very hairy, at the base of the midrib on the under side. The flowers are white, in dense, terminal, nodding panicles, and appear with the leaves. Calyx very small and 4-cleft. Corolla divided to the base into linear, drooping segments. Stamens 2; anthers yellow and incumbent. The pericarp is a winged key, not dehiscing (L.). The leaves on the same tree are said to be variable.
History and Description.—The manna tree is a native of most parts of southern Europe. The official part is the juice of the tree, known in commerce as "manna." Manna issues from the tree in part spontaneously from fissures, partly from punctures produced by an insect, but more generally from incisions daily made in the tree (one above another) during the warm summer months, from which the viscous, brown, bluish fluorescent, bitterish juice flows out, and speedily hardens, losing thereby its bitterness and becoming white. These incisions are repeated annually, and alternately upon opposite sides of the tree, each season, so long as it yields manna. One tree may yield manna for 20 years. There are several varieties of manna, which chiefly differ from one another in quality according to the season and mode of gathering. The Sicily manna (manna geraci) is the most esteemed. It is also called flake manna (manna cannulata)—large and small flake—and is procured from the incisions on the upper part of the tree, during the height of the season, when the juice flows vigorously. It is collected on straws or twigs, etc., upon which it concretes in stalactitic masses. Long keeping deepens its color. Its fracture is somewhat crystalline, due to the presence of crystals of mannite. The U. S. P. describes good manna as "in flattish, somewhat 3-edged pieces, occasionally 20 Cm. (8 inches) long and 5 Cm. (2 inches) broad, usually smaller; friable; externally yellowish-white; internally white, porous, and crystalline; or in fragments of different sizes, brownish-white and somewhat glutinous on the surface, internally white and crystalline; odor honey-like; taste sweet, slightly bitter and faintly acrid. On heating 5 parts of manna with 100 parts of alcohol to boiling, and filtering, the filtrate should rapidly deposit separate crystals of mannite. Manna consisting of brownish, viscid masses, containing few or no fragments of a crystalline structure, should be rejected"—(U. S. P.). The ordinary quality is common manna, or manna in sorts; this is gathered late in the season when the temperature is diminishing, so that the juice imperfectly concretes, and has to be exposed to the action of the sun to complete its drying. Pieces of manna picked up from the ground form part of this sort of manna. It is in masses of a similar color to, but of less size than the flake manna—joined by a soft, adhesive substance of a dark, yellowish-brown color; its taste is rather unpleasant. A third variety, termed fat manna, is gathered in the latter part of autumn, when the season is wet and cool, and, in consequence of which, it does not readily concrete. A fatty manna is also said to be procured from the incision made in the lower part of the tree, during the warmer months. Fat manna is less solid than the preceding varieties, adhesive, not brittle, of a yellowish-red or yellowish-brown color, of a strong honey odor, a mawkish, sweet, unpleasant taste, and mixed with sand, pieces of bark, and other foreign substances. There is not so much mannite present in this grade, but more of sugar, gum, etc. This is the kind of manna rejected by the Pharmacopoeia.
Manna softens with the heat of the hand, melts at a temperature somewhat higher, and is inflammable, burning with a blue flame, throwing out yellow sparks. Pure manna is almost entirely dissolved in 3 parts of water at 15.5° C. (60° F.), and 1 part at 100° C. (212° F.). From the latter solution it is deposited, on cooling, in crystalline forms. In consequence of the sugar contained in manna it is capable of undergoing fermentation.
Chemical Composition.—The principal constituent of pure manna is mannite (C6H8[OH]6), 90 per cent, with 11 per cent of sugar and about 0.75 per cent of impurities (Flückiger, Pharmacognosie, 1891, p. 27). Inferior sorts of manna contain mucilage, cane-sugar, laevulose, dextrin (Buignet, 1868; doubted by Flückiger), bitter substances soluble in ether, and fraxin (C16H18O10), a fluorescent glucosid resembling aesculin.
Mannite (mannitol) (C6H8[OH]6, or C6H14O6) may be readily prepared from manna by digesting it in hot alcohol; on cooling, the mannite forms in tufts of silky, quadrangular prisms. C. T. Bonsall's method consists in dissolving manna in boiling water (3 parts by weight), precipitation of the gum, etc., by lead subacetate, removal of lead with sulphuric acid or hydrogen sulphide, concentration, and pouring the hot solution in cold alcohol (2 parts), from which the mannite is deposited on cooling. Mannite is sweet, odorless, requiring about 6 parts of water to dissolve it, is readily dissolved in boiling alcohol, much less so in cold, deliquesces in the air, and does not dissolve in ether. Its solution possesses a feebly laevo-rotatory polarization. Mannite combines with bases, dissolves lime, reduces gold from its chloride solution, does not reduce Fehling's solution, forms oxalic and saccharic acids when heated with nitric acid, does not ferment when its solution is mixed with yeast, though it ferments when in contact with old cheese and chalk at 40° C. (104° F.), alcohol, lactic, butyric, acetic, and carbonic acids and hydrogen being produced. Unlike cane-sugar, mannite does not char under the action of sulphuric acid, and does not become, like grape-sugar, brown when heated with alkaline solutions. It fuses at about 165° C. (329° F.), without losing weight, and, on cooling, the colorless solution forms a mass of radiated crystals. At about 200° C. (392° F.), it sublimes partially unchanged, but a large portion of it becomes a sweetish, viscid liquid, mannitan (C6H12O5). It is also changed into fermentable mannitose (C6H12O6) and mannitic acid (C6H12O7) when in contact with moistened platinum black (Gorup-Besanez). Mannite also exists in Laminaria saccharina, onions, asparagus tops, celery, unripe olives, certain fungi, etc. It has also been procured from beet root, and the juice exuding from apple and pear trees. One or 2 ounces will, it is stated, act as a gentle laxative.
Action, Medical Uses, and Dosage.—Manna is nutritive in small doses, and mildly laxative in large ones. It operates without causing any local excitement or uneasiness, and is useful as a laxative for young infants, children, females during pregnancy and immediately after, inflammation of the abdominal viscera, disorders of childhood, hemorrhoids, costiveness, etc. It is accredited with cholagogue properties, and has a somewhat beneficial action upon the respiratory tract. It is commonly added to other purgatives to improve their flavor, as well as to increase the purgative effect. One or 2 ounces may be taken by an adult; 1, 2, or 3 drachms by a child, according to its age. Two or 3 parts of manna to 1 of senna maybe made into a laxative infusion for children. Sometimes manna causes flatulency and griping, which may be obviated by combining it with any grateful warm aromatic.
False Mannas.—Various other trees of the family Ornus and Fraxinus furnish manna, as the O. rotundifolia, O. parvifolia, O. subrufescens, O. lentiscifolia, F. excelsior, etc. The Abies or Pinus Larix (Larix europaea) yields a sweet exudation called BRIANÇON MANNA, or EUROPEAN FALSE MANNA, but which contains no mannite, but a principle called melezitose (C18H32O16.2H2O). The Alhagi Camelorum (Hedysarum Alhagi), of Syria, yields the MANNA MERENIABIN, an inferior manna. The Larix Cedrus produces the MANNA OF LEBANON; the Tamarix gallica, of North Africa, the MANNA OF MOUNT SINAI; it also yields tamarisk galls; and the Eucalyptus mannifera, a kind of manna called NEW HOLLAND MANNA, containing a saccharine principle, but no mannite. Other species of Eucalyptus yield AUSTRALIAN MANNA. There are several other mannas, such as PERSIAN MANNA, OAK MANNA, ORIENTAL MANNA, LERP, etc., for description of which see works specially treating on the subject. The manna of Scripture is now thought possibly to be the lichen Lecanora esculenta, which sometimes falls in showers from Persia to the Desert of Sahara. It makes a fairly good bread, and is eaten by the people. It is called manna. An AMERICAN MANNA, so called, is the product of an Oregon tree—the Pinus Lambertiana. It contains a non-fermentable, very sweet body called pinite (C6H12O5. The CALIFORNIA MANNA, described, in 1702, by the Jesuit Father Picolo, is most likely an exudation of the reed grass, Phragmites communis, caused by insects (see J. U. Lloyd, Amer. Jour. Pharm., 1897, p. 329).