Sex. Syst. Pentandria, Digynia.
(Cortex interior, L.)
History.—Dioscorides [Lib. i. cap. 111.] speaks of the astringent property of the bark of the elm (πτελεα), as does also Pliny. [Hist. Nat. lib. xxiv. cap. 33.]
Botany. Gen. Char.—Flowers hermaphrodite. Calyx campanulate, 4- to 5-toothed, coloured, persistent. Stamens 3 to 6. Ovary compressed. Stigmas 2. Fruit (a samara) suborbicular, with a broad membranous margin (Bot. Gall.).
Sp. Char.—Leaves doubly serrated, rough. Flowers nearly sessile, 4-cleft. Fruit oblong, deeply cloven, naked (Sir J. E. Smith).
A large tree, with rugged bark. By the latter character it is readily distinguished from Ulmus glabra, which has a smooth, dark, lead-coloured bark.
Hab.—Southern parts of England. Flowers in March or April.
Description.—The officinal part of the elm is the inner cortical portion, or liber. To obtain it, the bark should be separated from the tree in spring; and, after the epidermis and a portion of the external cortex have been removed, the liber should be quickly dried.
As met with in the shops, the inner elm bark (cortex ulmi) consists of thin tough pieces, which are inodorous, and have a brownish-yellow colour, and a mucilaginous, bitter, very slightly astringent taste.
Composition.—According to Rink, [Geiger, Handb. d. Pharm.; and Wittstein's Handworterbuch.] 100 parts of elm bark contain—resin 0.63, gum and mucus 20.3, impure gallic acid (tannin?) 6.5, oxalate of lime 6.3 (?), chloride of sodium (?) 4.6.
1. Tannic acid.—Davy [Phil. Trans. 1803, p. 233.] states that 480 grs. of elm bark yielded 13 grs. of tannin.
2. Ulmic acid; Ulmin.—On many trees, especially the elm, there is not unfrequently observed a substance which was supposed to be a morbid production. When dried, it consists of a mucilaginous matter, and carbonate or acetate of potash. By the combined agency of the air and the carbonate, the organic matter is altered in its properties, and is converted into a brown substance, which combines with the potash. This brown matter has been termed ulmin, or ulmic acid. It may be formed, artificially, by a variety of processes; as by heating a mixture of wood and potash, by the action of sulphuric acid on vegetable matters, and by other methods.
Chemical Characteristics.—Infusion of elm bark becomes green (tannate of iron) on the addition of a salt of the sesquioxide of iron, and forms a precipitate (tannate of gelatin) with a solution of gelatin.
Physiological Effects.—The effects of elm bark are those of a mild astringent tonic, containing a considerable quantity of mucilage, which gives it a demulcent property. Hence, in the classification of Richter, [Arzneimitt. Bd. i.] it is arranged as a mucilaginous astringent. The decoction, taken in full doses, accelerates the pulse and acts as a diaphoretic and diuretic.
Uses.—Lysons [Medical Transactions, vol. ii. p. 203.] recommended the decoction of this bark in cutaneous eruptions, and Dr. Lettsom [Medical Memoirs, p. 152.] found it successful in ichthyosis. It has now fallen almost into disuse. It has been employed as a cheap substitute for sarsaparilla. [Jeffreys, Cases in Surgery, Lond. 1820.]
Administration.—Used only in the form of decoction.
DECOCTUM ULMI, L.; Decoction of Elm Bark.—(Fresh Elm Bark, bruised, ℥ijss; Distilled Water Oij. Boil down to a pint, and strain.)—Formerly given in skin diseases; now fallen into disuse. Dose, f℥iv to f℥vj three or four times a day.