Birch, Common

Betula alba (LINN.)
Family: N.O. Betulaceae

Coleridge speaks of it as the 'Lady of the Woods.' It is remarkable for its lightness, grace, and elegance, and after rain it has a fragrant odour.

The young branches are of a rich red brown or orange brown, and the trunks usually white, especially in the second species of B. alba, B. verrucosa. B. pubescens is darker, and has downy instead of warted twigs.

The wood is soft and not very durable, but being cheap, and the tree being able to thrive in any situation and soil, growing all over Europe, is used for many humble purposes, such as bobbins for thread mills, herring-barrel staves, broom handles, and various fancy articles. In country districts the Birch has very many uses, the lighter twigs being employed for thatching and wattles. The twigs are also used in broom making and in the manufacture of cloth. The tree has also been one of the sources from which asphyxiating gases have been manufactured, and its charcoal is much used for gunpowder.

The white epidermis of the bark is separable into thin layers, which may be employed as a substitute for oiled paper and applied to various economical uses. It yields oil of Birch Tar, and the peculiar, well-known odour of russia leather is due to the use of this oil in the process of dressing. It likewise imparts durability to leather, and it isowing to its presence that books bound in russia leather are not liable to become mouldy. The production of Birch Tar oil is a Russian industry of considerable importance. It is also distilled in Holland and Germany, but these oils are appreciably different from the Russian oil. It has the property of keeping away insects and preventing gnatbites when smeared on the hands. It is likewise employed in photography.

When the stem of the tree is wounded, a saccharine juice flows out which is susceptible, with yeast, of vinous fermentation. A beer, wine, spirit and vinegar are prepared from it in some parts of Europe. Birch Wine, concocted from this thin, sugary sap of the tree, collected from incisions made in the trees in March, honey, cloves and lemon peel being added and then the whole fermented with yeast, makes a very pleasant cordial, formerly much appreciated. From 16 to 18 gallons of sap may be drawn from one large tree, and a moderate tapping does no harm.

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¶ Constituents.  Birch bark only contains about 3 per cent. of tannic acid, but is extensively used for tanning, wherever there are large birch forests, throughout Northern Europe. As it gives a pale colour to the skin, it is used for the preliminary and the final stages of tanning. It contains betulin and betuls camphor.

The leaves contain betulorentic acid.

By destructive distillation, the white epidermis of the bark yields an empyreumatic oil, known variously in commerce as oil of Birch Tar, Oleum Rusci, Oleum Betulinum or Dagget. This is a thick, bituminous, brownish-black liquid, with a pungent, balsamic odour. It contains a high percentage of methylsalicylate, and also creosol and guaiacol. The Rectified Oil (Oleum Rusci Rectificatum) is sometimes substituted for oil of Cade.

Birch Tar oil is almost identical with Wintergreen oil. It is not completely soluble in 95 per cent. acetic acid, nor in aniline, but Turpentine oil dissolves it completely.

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¶ Medicinal Action and Uses.  Various parts of the tree have been applied to medicinal uses. The young shoots and leaves secrete a resinous substance having acid properties, which, combined with alkalies, is said to be a tonic laxative. The leaves have a peculiar, aromatic, agreeable odour and a bitter taste, and have been employed in the form of infusion (Birch Tea) in gout, rheumatism and dropsy, and recommended as a reliable solvent of stone in the kidneys. With the bark they resolve and resist putrefaction. A decoction of them is good for bathing skin eruptions, and is serviceable in dropsy.

The oil is astringent, and is mainly employed for its curative effects in skin affections, especially eczema, but is also used for some Internal maladies.

The inner bark is bitter and astringent, and has been used in intermittent fevers.

The vernal sap is diuretic.

Moxa is made from the yellow, fungous excrescences of the wood, which sometimes swell out from the fissures.

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¶ Dosage.  Of alcoholic extract of the leaves, 25 to 30 grains daily.

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¶ Other Species. 
B. benta (Cherry Birch, Black Birch, Sweet Birch, Mahogany Birch, or Mountain Mahogany) is an American variety, with richlymarked wood suitable for the use of cabinet and pianoforte makers. The liquor is used in Kamschatka without previous fermentation. The cambium, or the layer between the wood and the bast, is eaten in the spring, cut into strips like vermicelli, and the bark is stimulant, diaphoretic, and astringent, in a warm infusion. In decoction or syrup it forms an excellent tonic for dysentery, and is said to be useful in gravel and female obstructions.

B. trophylla is a syn. of Rhus Aromatica, or Fragrant Sumach.

B. papyracea, or Paper Birch, is largely used for canoe-making in America.

B. nana, or Smooth Dwarf Birch, rarely grows above 3 feet in height. The leaves are said to dye a better yellow than the Common Birch; the seeds are a principal food of ptarmigan in Lapland; Moxa is prepared from it and regarded as an effective remedy in all painful diseases.

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