_Rhizoma Arnicæ_, _Arnica Root_; F. _Racine d’Arnica_; G.
_Arnicawurzel_.
=Botanical Origin=—_Arnica montana_ L., a perennial plant growing in
meadows throughout the northern and central regions of the northern
hemisphere, but not reaching the British Islands. In western and
central Europe it is an inhabitant of the mountains, but in colder
countries it grows in the plains.
In high latitudes, as in Arctic Asia and America, a peculiar form of
the plant distinguished by narrow, almost linear leaves has been named
_A. angustifolia_ Vahl; but numerous transitional forms prove its
identity with the ordinary _A. montana_ of Europe.
=History=—The older botanists as Matthiolus, Gesner, Camerarius,
Tabernæmontanus, and Clusius were acquainted with Arnica and had some
knowledge of its medicinal powers, which appear to have been expressly
recommended, towards the end of the 16th century, by Franz Joël,
professor of Greifswald, Germany.[1440] All parts of the plant were no
doubt popular remedies in Germany at an early period, but Arnica was
only introduced into regular medicine on the recommendation of Johann
Michael Fehr of Schweinfurt and of several other physicians.[1441] But
for enthusiastic laudation of the new remedy, all these writers fall
far short of Collin of Vienna, who imagined that in Arnica he had found
a European plant possessing all the virtues of Peruvian Bark.[1442] In
his hands fevers and agues gave way under its use, and more than 1000
patients in the Pazman Hospital were alleged to have been cured of
intermittents by an electuary of the flowers, between 1771 and 1774.
Such happy results were not obtained by other physicians.
[1440] Sprengel, _Geschichte der Arzneykunde_, iv. (1827) 546.
[1441] Fehr, _De Arnica lapsorum panacea, in Ephemerid. nat. cur._
Dec. 1, (1678, 1679) No. 2. p. 22 (“usus est in _radice_, _foliis_ et
_floribus_”).—G. A. de la Marche, _Dissertatio_, Halæ Magdeburg, 1744.
[1442] Heinrich Joseph Collin, _Heilkräfte des Wolverley_, Breslau,
1777 (translation); also _Arnicæ, in febribus et aliis morbis putridis
vires_,—in the _Anni Medici_ of Störck and Collin, ed. nov., Amstel.,
iii. (1779) 133.
Arnica (_herba_, _flos_, _radix_) had a place in the London
Pharmacopœia of 1788, but it soon fell out of notice, so that Woodville
writing in 1790, remarks that he had been unable to procure the
plant from any of the London druggists. Of late years it has gained
some popular notoriety as an application in the form of tincture,
for preventing the blackness of bruises, but in England it is rarely
prescribed internally.
=Description=—The arnic root of pharmacy consists of a slender,
contorted, dark brown rootstock, an inch or two long, emitting from its
under side an abundance of wiry simple roots, 3, 4 or more inches in
length; it usually bears the remains of the rosette of characteristic,
ovate, coriaceous leaves, which are 3-to 5-nerved, ciliated at the
margin, and slightly pubescent on their upper surface. It has a faintly
aromatic, herby smell, and a rather acrid taste.
=Microscopic Structure=—On a transverse section, the rootstock exhibits
a large pith surrounded by a strong woody ring. In the innermost part
of the cortical layer, large oil-ducts are found corresponding to the
fibro-vascular bundles. Neither starch granules, inulin, or oxalate
of calcium are visible in the tissue. The rootlets are of a different
structural character, but also contain oil-ducts.
=Chemical Composition=—Several chemists have occupied themselves
in endeavouring to isolate the active principle of arnica. Bastick
described (1851) a substance which he obtained in minute quantity from
the flowers and named _Arnicine_. He states it to possess alkaline
properties, to be non-volatile, slightly soluble in water, more so in
alcohol or ether; when neutralized with hydrochloric acid, it forms a
crystalline salt.
The _Arnicin_ extracted by Walz (1861) both from the root and flowers
of arnica is a different substance; it is an amorphous yellow mass of
acrid taste, slightly soluble in water, freely in alcohol or ether,
and dissolving also in alkaline solutions. It is precipitable from its
alcoholic solution by tannic acid or by water. Walz assigns to arnicin
the formula C₂₀H₃₀O₄; other chemists that of C₃₅H₅₄O₇. Arnicin has not
yet been proved a glucoside, although it is decomposed by dilute acids.
Sigel (1873) obtained from dried arnica root about ½ per cent.
of essential oil, and 1 per cent. from the fresh; the oil of the
latter had a sp. gr. of 0·999 at 18° C. The oil was found to be a
mixture of various bodies, the principle being _dimethylic ether of
thymohydroquinone_
{OCH₃
C₁₀H₁₂ { , boiling at about 235°.
{OCH₃
The water from which the oil separates contains _isobutyric acid_,
probably also a little _angelic_ and _formic acid_; but neither
capronic nor caprylic acid, which had been pointed out by Walz.
Arnica root contains _inulin_, which Dragendorff extracted from it to
the extent of about 10 per cent.
=Uses=—Arnica is used chiefly in the form of tincture as a popular
application to bruises and chilblains; internally it is occasionally
prescribed as a stimulant and diaphoretic.
=Adulteration=—Arnica root has been met with[1443] adulterated with
the root of _Geum urbanum_ L., a common herbaceous plant of the order
_Rosaceæ_. The latter is thicker than the rhizome of arnica, being
³/₁₀ to ⁴/₁₀ of an inch in diameter; it is a true _root_, furnished on
all sides with rootlets, and has an _astringent_ taste. The leaves of
_Geum_ are pinnate and quite unlike those of arnica.
[1443] Holmes in _Pharm. Journ._, April 11, 1874. 810.