This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
Arnica flowers are the flowerheads of Arnica montana, Linne (N.O. Compositoe), a small plant with creeping perennial rhizome, indigenous to central Europe. In the warmer districts it is common in the meadows on the lower mountain spurs; in the more northern districts it grows in the valleys. It produces large, solitary, orange-yellow flowerheads, not unlike yellow marguerites, measuring about
7 cm. in diameter.
The flowerheads are usually collected entire and dried; the receptacle being especially liable to be attacked by insects, this, together with the involucre, is sometimes separated, and the drug then consists of the ligulate and tubular florets but this variety is not official.
The drug as met with in English commerce commonly consists of the entire flowerheads, the most conspicuous parts of which are the green involucre and whitish, bristly pappus; the dark yellow ligulate corolla, so prominent in the fresh flower, shrivels so much as to become quite inconspicuous.
The involucre consists of two rows of dark green, acutely pointed, linear-lanceolate, hairy bracts. The florets of the ray are pistillate, and possess long, narrow, dark yellow ligulate corollas containing about seven to nine veins and terminated by three teeth.
The disc-florets are numerous, and have a long, dark yellow, tubular corolla which bears on its outer surface minute glands, visible under a strong lens; similar glands are found also on the ligulate ray-florets. The fruit, which is more or less shrivelled, is elongated, straight, covered with appressed hairs, and surmounted by a single ring of stiff, whitish, barbed bristles (pappus); the hairs consist of two long, narrow, contiguous cells which are divergent at the apex and pointed, but this character can scarcely be seen under a lens.
After the florets have been removed, the receptacle, which is about
8 mm. in diameter and arched, exhibits a corresponding number of depressions, each of which bears in its centre a stiff, dark bristle, and is surrounded by short, bristly hairs, the latter being, however, sometimes absent.
Arnica flowers have a slight pleasant odour, and bitter, rather acrid taste.
The student should particularly note
(a) The narrow, ligulate corollas, with from seven to nine veins and three teeth,
(b) The straight, bristly fruit and abundant, whitish, bristly pappus,
Fig. 43. - Arnica flower. Natural size. (Pharmaceutical Journal).
(c) The linear-lanceolate, hairy, involucral bracts,
(d) The characteristic twin hairs on the fruit.
Arnica flowers contain traces of volatile oil and a bitter principle, arnicin, which has been obtained in minute, yellow, deliquescent crystals. The flowers are said to contain more arnicin than the rhizome. The drug also contains tannin, resin, yellow colouring matter and a phytosterin, arnisterin.
Preparations of arnica flowers applied to the skin appear to increase the activity of the circulation, and the tincture, diluted with water, is used for application to the skin; internally they are stimulant and irritant, but they are now seldom administered.
Of the numerous other composite flowers reported to have been mixed with or sold for arnica, the following may be mentioned.
Anthemis tinctoria, Linne; fruits without pappus; paleae on receptacle.
Calendula officinalis, Linne; ligulate corolla with four veins; fruit-without pappus.
Inula britannica, Linne; ligulate corolla with four veins; pappus not bristly. Arnica from the Italian Alps is frequently derived from I. britannica.
Doronicum pardalianches, Linne; ligulate corolla with four veins; no pappus.
Taraxacum sp.; Scorzonera sp.; all florets with 5-toothed ligulate corollas.
Fig. 44. - Arnica flowers. A, ray-floret. B, disc-floret. C, the same, cut vertically: o, ovary; p, pappus; a, anthers. All magnified. (Luer-ssen).