Comfrey, the Common, or Symphytum officinale, L. a native perennial plant, which grows about two feet high, is found on the banks of rivers, and wet ditches ; and produces yellow-white flowers, in the months of May and June. It is eaten by sheep and cows, but horses, goats, and hogs refuse it. The leaves of this plant impart a grateful flavour to cakes and panada; the young stems, when boiled, are excellent and nutritious eating. A decoction of the stalks, with leaves and flowers, gives to wool prepared by a solution of bismuth, a fine and permanent brown colour.
But the moat useful part of the Comfrey, is its viscid and mucilaginous root, which may be classed among the neglected treasures of the vegetable kingdom. These roots are, at present, chiefly employed by colour-makers, who, by means of a decoction made of them, extract the beautiful crimson colour from gum-lac. The natives of Angora, who possess the finest breed of goats in the world, prepare from the comfrey-roots a kind of glue, that enables them to spin the fleece into a very fine yarn, from which camblets (See vol. i. p. 425) and shawls are manufactured. The Germans have lately employed the same mucilage for correcting the brittleness of flax, and roughness of wool, in spinning : this preparation neither soils the fingers nor the yarn, and may be preserved in a fresh state for many days, in close wooden boxes. Tabernamontan, in his German Herbal, relates a curious fact, which, if not exaggerated, would" be of great value in the important process of tanning, and rendering leather water-proof. He boiled, in a pailful of water, ten pounds of the fresh root, dug out in November, till one half the liquor was evaporated: with this decoction, when cool, he repeatedly dressed the leather which, thus prepared, became not only more durable than by any other method, but it always remained pliable and elastic. - M. DorffuRth, an apothecary of Wittenberg, in Germany, also employed these roots in his experiments on tanning, with considerable success. Alter drying and reducing them to powder, or cutting the fresh roots into small pieces, he infused them in a proportionate quantity of water, frequently stirring the mass, till it acquired the consistence of treacle. It was then allowed to stand at rest several days, till the fibrous and woody part had subsided, when the clear fluid was poured off or passed through a basket lined with straw. By dropping diluted oil of vitriol into this liquor, he plecipitated the mucilaginous part, which was again filltred and rendered tit for another process of tanning, after depriving it of its acidity, by means of a lye made of common pot-ash. - Another German writer, M. REUSS, mentions the root of the comfrey among those plants, from which good starch and hair-powder may be prepared.