(Quercus Pedunculata. _Cortex._)
_Oak Bark._
QUALITIES. _Odour_, none; _taste_, rough and astringent. CHEMICAL
COMPOSITION. We are indebted to Sir H. Davy for a knowledge of this
subject; he found that an ounce of the inner cortical part of young oak
bark afforded by lixivation 111 grains of solid matter, of which 77 were
_tannin_; and the cellular integument, or middle-coloured part, only
yielded 43 grains of solid matter, of which 19 were _tannin_; and the
epidermis furnished scarcely any quantity of _tannin_ or extractive;
hence the bark should be selected from the smaller branches of the oak
where the epidermis is still thin. Experience has, moreover, shewn that
the quantity of _tannin_ varies considerably, not only according to the
age and size of the trees, but according to the season at which they are
_barked_; thus, the bark cut in spring contains, according to
_Beguin_,[620] four times more of the astringent principle, than that
which is obtained in winter. MED. USES. All its properties depend upon
the presence of _tannin_, it is therefore only valuable as a powerful
astringent; it is accordingly employed to check inordinate discharges,
see _Decoctum Quercus_. Oak bark is sometimes administered in the form
of powder, combined with ginger and other aromatics, and bitters, for
the cure of intermittents, and it has frequently succeeded, but see page
167. Dose, ℈j to ʒss. In the form of poultice this powder is said to
have proved highly useful to gangrenous sores. Its inhalation has also
been supposed to prove beneficial in consumption; a striking case is
related by Dr. Eberle of a man who had laboured under the usual symptoms
of confirmed Phthisis, and who, at the time he went to grind in a
bark-mill, was extremely weak and emaciated; in a short time, however,
the cough, night sweats, and other hectic symptoms, began to abate
sensibly, and in less than three months he was perfectly restored to
health.