_Mezereon Bark_; F. _Ecorce de Mézéréon_, _Bois gentil_; G.
_Seidelbast-Rinde_.
=Botanical Origin=—_Daphne Mezereum_ L., an erect shrub, 1 to 3 feet
high, the branches of which are crowded with purple flowers in the
early spring, before the full expansion of the oblong, lanceolate,
deciduous leaves. The flowers are succeeded by red berries. It is a
native of the hilly parts of almost the whole of Europe, from Italy
to the Arctic regions, and extends eastward to Siberia. In Britain it
occurs here and there in a few of the southern and midland counties,
and even reaches Yorkshire and Westmoreland, but there is reason to
think it is not truly indigenous. Gerarde, who was well acquainted with
it, did not regard it as a British plant.
=History=—The Arabian physicians used a plant called _Mázariyún_,
the effects of which they compared to those of euphorbium; it was
probably a species of _Daphne_. The word _mázariyún_ is, we are told by
competent Arabic scholars, not of Arabic origin, but in all probability
derived from the Greek idiom, in which however we are unable to trace
its origin. _D. Mezereum_ was known to the early botanists of Europe,
as _Daphnoides Chamælæa_, _Thymelæa_, _Chamædaphne_. Tragus described
it and figured it in 1546 under the name of _Mezereum Germanicum_. The
bark had a place in the German pharmacy of the 17th century under the
name of cortex _Coccognidii_ s. _Mezerei_; the berries were the _Cocca
gnidia_ s. _knidia_ of the old pharmacy.
=Description=—Mezereon has a very tough and fibrous bark easily
removed in long strips which curl inwards as they dry; it is collected
in winter and made up into rolls or bundles. The bark, which rarely
exceeds ¹/₂₀ of an inch in thickness, has an internal greyish or
reddish-brown corky coat which is easily separable from a green inner
layer, white and satiny on the side next the wood. That of younger
branches is marked with prominent leaf-scars. The bark is too tough to
be broken, but easily tears into fibrous strips. When fresh, it has an
unpleasant odour which is lost in drying; its taste is persistently
burning and acrid. Applied in a moist state to the skin, it occasions,
after some hours, redness and even vesication.
=Microscopic Structure=—The cambial zone is formed of about ten rows
of delicate unequal cells. The libre consists chiefly of simple fibres
alternating with parenchymatous bundles, and traversed by medullary
rays. The fibres are very long,—frequently more than 3 mm., and from 5
to 10 mkm. in diameter, their walls being always but little thickened.
In the outer part of the liber there occur bundles of thick-walled
bast-tubes, while chlorophyll and starch granules appear generally
throughout the middle cortical layer. The suberous coat is made up of
about 30 dense rows of thin-walled tabular cells, which examined in
a tangential section, have an hexagonal outline. Small quantities of
tannic matter are deposited in the cambial and suberous zones.
=Chemical Composition=—The acrid principle of mezereon is a resinoid
substance contained in the inner bark; it has not yet been examined.
The fruits were found by Martius (1862) to contain more than 40 per
cent. of a fatty, vesicating oil, which appears to be likewise present
in the bark.
The name _Daphnin_ has been given to a crystallizable substance
obtained by Vauquelin in 1808 from _Daphne alpina_, and afterwards
found by C. G. Gmelin and Baer in the bark of _D. Mezereum_. Zwenger
in 1860 ascertained it to be a glucoside of bitter taste, having
the composition C₁₅H₁₆O₉ + 2 OH₂, the same as that of Æsculin, the
fluorescing principle occurring in the bark of _Æsculus Hippocastanum_
and the root-bark of _Gelsemium nitidum_ Michaux (_G. sempervirens_
Aiton).—_Coccognin_, isolated in 1870 by Casselmann from the fruits of
_D. Mezereum_, appears to be closely allied to if not identical with
daphnin.
When daphnin is boiled with dilute hydrochloric or sulphuric acid,
it furnishes _Daphnetin_, C₉H₆O₄ + OH₂, described by Zwenger as
crystallizing in colourless prisms. By dry distillation of an alcoholic
extract of mezereon bark, the same chemist obtained _Umbelliferone_ (p.
322).
=Uses=—Mezereon taken internally is supposed to be alterative and
sudorific, and useful in venereal, rheumatic and scrofulous complaints;
but in English medicine it is never now given except as an ingredient
of the Compound Decoction of Sarsaparilla. An ethereal extract of
the bark has been introduced (1867) as an ingredient of a powerful
stimulating liniment. On the Continent, the bark itself, soaked in
vinegar and water, is applied with a bandage as a vesicant.
=Substitutes=—Owing to the difficulty of procuring the bark of the
root of _D. Mezereum_, the herbalists who supply the London druggists
have been long in the habit of substituting that of _D. Laureola_ L.,
an evergreen species, not uncommon in woods and hedge-sides in several
parts of England. The _British Pharmacopœia_ (1864 and 1867) permits
_Cortex Mezerei_ to be obtained indiscriminately from either of these
species, and does not follow the London College in insisting on the
_bark of the root_ alone. That of the stem of _D. Laureola_ corresponds
in structure with the bark of the true mezereon, but wants the
prominent leaf-scars that mark the upper branches of the latter; it is
reputed to be somewhat less acrid than mezereon bark. The mezereon bark
of English trade is now mostly imported from Germany, and seems to be
derived from _D. Mezereum_.
In France, use is made of the stem-bark of _D. Gnidium_ L., a
shrub growing throughout the whole Mediterranean region as far as
Morocco. The bark is dark grey or brown, marked with numerous whitish
leaf-scars, which display a very regular spiral arrangement. The leaves
themselves, some of which are occasionally met with in the drug, are
sharply mucronate and very narrow. As to structural peculiarities,
the bark of _D. Gnidium_ has the medullary rays more obvious and more
loaded with tannic matters than those of _D. Mezereum_; but the middle
cortical layer is less developed. The bark, which is called _Ecorce de
Gaoru_, is employed as an epispastic.