Quercus Robur, Linn.
Sex. Syst. Monoecia, Polyandria.
(Cortex, L.—The Bark, E. D.)
History.—The oaks (Quercus of botanists) were held sacred by the Greeks, Bomans, Gauls, and Britons. They are mentioned in the Old Testament. [Isaiah, i. 28, 30.] Both Dioscorides and Galen were acquainted with their astringent qualities. "Every part of the oak" (δρυς; Q. sessiliflora and pedunculata according to Fraas, but according to Sibthorp Q. Aegilops), says Dioscorides, [Lib. i. cap. 142.] "but especially the liber, possesses an astringent property."
Botany. Gen. Char.—Monoecious. Male flowers: Catkins lax and pendulous. Perianth lacerated. Stamens 5 to 10. Female flowers: Involucre scaly; the scales numerous, imbricated; combined with a coriaceous, hemispherical cup. Perianth 6-lobed, adnate to the ovary. Ovary 3-celled; 2 of the cells abortive. Stigmas 3. Nut 1-celled, 1-seeded, surrounded at the base by the cupule (acorn-cup). (Bot. Gall.)
A large and handsome tree, remarkable for its longevity. Twigs round, smooth, grayish-brown. Leaves bright green, furnished with a single midrib sending off veins into the lobes. Male flowers yellowish; females greenish, tinged with brown.
The long peduncles which support the female catkins have given the name of pedunculata or long-stalked to this species of Quercus or Oak.
Hab.—Indigenous, growing in woods and hedges. Flowers in April. It is found in most European countries.
Barking.—In the spring, the barks of trees contain more astringent matter, and are more readily separated from the wood. The usual time for barking the oak is from the beginning of May to the middle of July. The barkers make a longitudinal incision with a mallet furnished with a sharp edge, and a circular incision by means of a barking-bill. The bark is then removed by the peeling-irons, the separation being promoted, when necessary, by beating the bark with the square end of the mallet. It is then carefully dried in the air, by setting it on what are called lofts or ranges, and is afterwards stacked. [Loudon's Encyclopaedia of Agriculture, 3d edit. pp. 658-9.]
Description.—Oak bark (cortex quercus) consists of pieces of from one to two feet long, which vary in their appearance according to the age of the stem or branch from which they have been taken. The bark of young stems is thin, moderately smooth, covered externally with a silvery or ash-gray cuticle, and is frequently beset with lichens. Internally it is, in the fresh state, whitish; but, when dried, brownish, red, fibrous. The bark of old stems is thick, very rough externally, cracked, and wrinkled, and is usually of inferior quality.
Composition.—According to Braconnot, [Ann. de Chim. et de Phys. t. l. p. 381.] oak bark contains—tannic acid, tannates of lime, magnesia, potash, &c, gallic acid, uncrystallizable sugar, pectin, and lignin.
The quantity of Tannin [impure tannic acid] obtained by Davy [Elem. of Agricult. Chem. 4th edit. p. 83.] from oak bark, is as follows:—
|480 lbs of||Tannin afforded.|
|Entire bark of middle-sized oak, cut in spring||29 lbs.|
|Entire bark of coppice oak||32 lbs.|
|Entire bark of oak, cut in autumn||21 lbs.|
|White interior cortical layers of oak bark||72 lbs.|
Biggins [Pfaff, Syst. d. Mat. Med. Bd. ii. S. 207.] obtained 30 parts of tannin from the bark of an oak felled in winter, while the same weight of the bark of an oak felled in spring yielded him 108 parts.
Chemical Characteristics.—Decoction of oak bark reddens litmus, and becomes dark blue or purple (tannate of iron) on the addition of sesquichloride of iron. A solution of gelatin causes a precipitate (tannate of gelatin) with it. It is somewhat remarkable, however, that a solution of emetic tartar causes no precipitate with the decoction. [If alcohol be added to the decoction, concentrated to the consistence of a syrup, it causes the precipitation of pectin. A decoction, rendered alkaline by a fixed alkali, deposits a gelatinous matter (pectic acid) on the addition of acetic acid. Braconnot.]
Physiological Effects.—The effects of oak bark are similar to those of other vegetable astringents containing tannic acid, and have been already described (see vol. i., p. 201).
Uses.—The principal value of oak bark in medicine arises from its astringent property. Thus we employ a decoction of it as a gargle in relaxed conditions of the uvula, and in chronic inflammatory affections of the throat; [Cullen, Mat. Med. vol. ii. p. 45.] as a wash in flabby, ill-conditioned, or bleeding ulcers; as an injection in leucorrhcea, in piles, or in prolapsus of the uterus or rectum; as an internal astringent in old diarrhoeas, in the last stage of dysentery, in alvine hemorrhages, &c. Poultices made of powdered oak bark have been applied with benefit to mortified parts. [Barton, Collection towards a Mat. Med. of the United States.] Mr. Lizars [Ed. Med. and Surg. Journal, July 1822.] states that he has obtained "wonderful success" in the cure of reducible hernia: by bathing the groin (the hernia having been previously reduced) three or four times daily with a warm inspissated decoction of oak bark, and then applying a truss. The practice, however, is not a new one. [See the references in Plouequet's Literatura Medica, t. ii. p. 297.]
The inhalation of finely-powdered oak bark is said to have proved very beneficial in supposed cases of pulmonary consumption. [Eberle, Treatise on Mat. Med. 2d edit. vol. i. p. 268.] I have already noticed (see vol. i., p. 175) the inspiration of impalpable powders of other astringents as a remedy for phthisis. Connected with this, the popular opinion of the exemption of operative tanners from phthisis pulmonalis deserves to be mentioned. Dr. Dods, [Lond. Med. Gaz. vol. iii. p. 479.] who has paid some attention to this subject, concludes, that the popular notion is correct; and he ascribes the exemption to "the inhalation of that peculiar aroma, or volatile matter, which is constantly arising from tan-pits during the process of tanning with bark." Hitherto, however, no sufficient evidence has been advanced to prove that tanners are exempt from the disease.
As a tonic, oak bark has been employed in medicine, but it is much inferior to the cinchona. Baths made of a decoction of this substance have been used by Dr. Eberle in the intermittents of very young children with benefit; and Dr. Fletcher, of Virginia, has recommended the same remedy in tabes mesenterica. [Eberle, op. cit. vol. i. pp. 267-8.] The decoction, powder, and extract, have been taken internally in intermittents, but they are very apt to irritate the stomach. Dr. Cullen [Mat. Med. vol. i. p. 45.] says, that both by itself, and joined with chamomile flowers, he has prevented the paroxysms of intermittents.
Administration.—Dose of the powder from half a drachm to one or two drachms.
DECOCTUM QUERCUS, L. E. D.; Decoction of Oak Bark.—(Oak Bark, bruised, ℨx [℥iss, D.]; Water [Distilled, L.] Oij [Oiss., D]. Boil down to a pint and strain.)—Used as a local astringent for various purposes, in the form of gargle, injection, or lotion. Administered in doses of f℥ii to f℥vi. Sometimes employed as a bath, especially for children.
The Elements of Materia Medica and Therapeutics, Vol. II, 3th American ed., was written by Jonathan Pereira in 1853.