The seed of Linum usitatissimum, Linné"—(U. S. P.).
COMMON NAMES:Flaxseed, Linseed (Lini semina, Br. Pharm., 1885).
ILLUSTRATION: Bentley and Trimen, Med. Plants, 39.
Botanical Source.—Flax is an annual plant, very smooth, with a slender fibrous root, and 1 or more straight, round, leafy corymbose stems, 1 or 2 feet in height. The leaves are small, alternate, sessile, acute, 3-veined, and rather glaucous; the lowermost short and blunt. The flowers are several, large, blue, erect, borne in a terminal, corymbose panicle, on long footstalks. The calyx is persistent, consists of 5 ovate, acute sepals, which are 3-veined at base, and membranaceous on the margin. The corolla is composed of 5 thin, delicate, roundish, wedge-shaped, crenate petals, which are glossy, have numerous veins, and readily drop off. Stamens 5, straight, and awl-shaped. Anthers 2-celled, and arrow-shaped. Ovary ovate, superior; styles 5; stigmas obtuse. The fruit is a round capsule, 5-celled, the cells nearly divided by a false dissepiment; seeds 2 in each cell, ovate, compressed, brown, smooth, and glossy (L.—W.—Torrey and Gray).
History.—The native country of flax is unknown, though supposed to be derived from Egypt, or from Central Asia. It has been known from remote antiquity (see Gen. xli, 42, and Exod. ix, 31). It is now naturalized in nearly all civilized countries. It blossoms from May to August, and matures its seeds early in autumn. The seeds and their expressed oil are used in medicine. The seeds are described by the U. S. P. as follows:
"About 4 or 5 Mm. (1/6 to 1/5 inch) long, oblong-ovate, flattened, obliquely pointed at one end, brown, glossy, covered with a transparent, mucilaginous epithelium, which swells considerably in water; the embryo whitish or pale greenish, with 2 large, oily, plano-convex cotyledons, and a thin perisperm; inodorous; taste mucilaginous, oily, and bitter. Ground linseed (linseed meal, or flaxseed meal), for medicinal purposes, should be recently prepared, free from unpleasant or rancid odor. When extracted with carbon disulphide, it should yield not less than 25 per cent of fixed oil. The filtered infusion of ground linseed, prepared with boiling water and allowed to cool, has an insipid, mucilaginous taste, and should not be colored blue by iodine T. S. (absence of starch)"—(U. S. P.). In this connection see paper by J. U. Lloyd, on the testing of flaxseed for starch, in the Pharm. Rundschau, 1895, p. 210.
Oil-cake (cake-meal, when ground) is the compressed refuse portion remaining after the oil has been pressed out; it contains the mucilage of the husk and all of the nitrogenous matter of the seed in condensed form (about 5 per cent nitrogen), and is therefore used to feed cattle. Starch should be absent from the cake, and the ash should not exceed 5 per cent. The seeds finely ground, furnish a dark, ash-colored powder, flaxseed meal, which forms with hot water a tenacious substance, used for luting in chemical operations. For poultices, the official Ground linseed (Farina lini, or Linseed meal) is the best.
Chemical Composition.—The chief constituents of flax seeds are mucilage (about 6 percent), residing in the epithelial cells of the epidermis, and fixed oil (see Oleum Lini, linseed oil), contained in the cotyledons (from 25 to 33 per cent; as high as 38 per cent, W. A. Puckner, Amer. Jour. Pharm., 1889, p. 442). Starch is absent in ripe seeds. (An adulteration of linseed meal with 40 per cent of corn meal is on record; see G. M. Beringer, Amer. Jour. Pharm., 1889, p. 167.) The mucilage probably has its origin in the starch occurring in the unripe seeds. When the unbruised seeds are covered with water, a viscid, odorless, and almost tasteless mucilage is obtained, precipitable by alcohol. When deprived of its ash (amounting to 10 per cent), the composition of the mucilage corresponds to the formula C12H20O10 (Tollens & Kirchner, 1874). It is precipitated also by basic acetate of lead, but not by tannic acid. It is not colored blue by the addition of iodine and sulphuric acid, nor does it redden litmus when in fresh condition. Boiling with diluted sulphuric acid produces mostly a dextro-rotatory sugar, and about 5 per cent of insoluble cellulose. Nitric acid converts it partly into mucic acid, oxalic acid being likewise formed.
Flax seeds contain about 4 per cent of nitrogen, corresponding to about 25 per cent of protein bodies. Part of the nitrogen is due, however, to the presence of a crystallizable, bitter substance formerly believed to be amygdalin, but differentiated from it as linamarin (Jorissen and Hairs, see Jahresb. der Pharm., 1891, p. 114). The presence of this substance gives rise to the frequently observed formation of hydrocyanic acid in ground flaxseed meal by spontaneous fermentation (see A. Jorissen, Jahresb. der Pharm., 1883 and 1894; and W. O. Senior, Pharm. Jour. Trans., 1885, Vol. XVI, p. 514). The seeds contain on an average 3.6 per cent of ash, which is rich in phosphoric acid (Amer. Jour. Pharm., 1881, p. 552). (As regards the manufacture and composition of linseed cake and meal, as well as enumeration of the possible impurities by weeds, etc., consult interesting article in Amer. Jour. Pharm., 1893, p. 195.)
Action, Medical Uses, and Dosage.—Flaxseed is used as a demulcent and emollient. An infusion of the entire seeds, an ounce to a quart of water at 100° C. (212° F.), forms a mucilaginous draught which is much employed in ardor urinae and urinary diseases, nephritic pains, coughs, colds, colo-rectitis, pulmonary, gastro-enteric, and urinary inflammations. When not contraindicated, the addition of lemon juice improves the flavor, or it may be sweetened with loaf sugar or honey. An infusion of flaxseed, or of flaxseed meal, forms an excellent laxative injection; and the meal added to boiling water, and made of the proper consistence, makes an excellent cataplasm (see Cataplasma Lini). Dose of the infusion, 1 or 2 pints daily. Ɣ Linseed oil in doses of 2 fluid ounces twice a day, is said to have cured severe cases of piles within 2 or 3 weeks; while using it liquors and stimulating diet are to be avoided. It is likewise reputed beneficial when internally administered in dysentery, colic, and lumbricus. Used as an enema it is advantageous in dysentery, hemorrhoids, and ascarides; and combined with lime-water, it forms Carron oil, an excellent application to burns. One pint of linseed oil, combined with 1/2 ounce each, of oils of origanum and wintergreen, forms a pleasant cathartic; to be given in the same doses as castor oil.
Related Species.—Linum catharticum, Purging flax. This is a European annual bearing very small white flowers, and having a very bitter subacrid taste. Water extracts its virtues, the infusion being yellow. The active cathartic principle is linin, which occurs in neutral, white, silky, and lustrous crystals. It is most abundant in the plant just after the flowers have fallen. Its alcoholic solution is persistently and strongly bitter. (For further details, see Husemann and Hilger, Pflanzenstoffe, 1884, p. 899.) Purging flax has the reputation on the continent of being mildly purgative, and has been employed in hepatic, catarrhal, and rheumatic disorders. The dose of the powdered plant is 1 drachm; of the extract, 4 to 8 grains. Diuretic properties are also ascribed to it.
King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.