Arnica
2 of the 7 encyclopedias on this shelf carry an entry for Arnica. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
Important: Safety Warning This page prescribes plants as medicine according to pre-modern medical theory. Several of the plants named are toxic, correct identification is difficult, and the doses given have no scientific basis. Do not ingest or apply any preparation described here. In addition, this page presents medical treatment from an era before modern medicine. The remedies described are ineffective against the conditions named, and some of the ingredients or doses are harmful. Do not use them to treat any illness; consult a qualified medical professional. This information has been left in for historical purposes but should not be acted upon. a genus of plants belonging to the order asteraceæ, or composites; also the English name of plants belonging to the above-mentioned genus, and especially of the A. montana, the mountain arnica, or German leopard's-bane. It is common in the alpine parts of Germany, Sweden, Lapland, and Switzerland. It is a perennial, of a slightly fetid odor, and a bitterish, acrid taste. Given in large quantities it produces deleterious effects, but the powdered leaves, in moderate doses, of 5 to 10 grains, have been found serviceable in paralysis, convulsions, amaurosis, chlorosis, gout, and rheumatism. As an outward application, arnica is in constant use as a remedy for sores, wounds, bruises, and ailments of a similar kind.
Aiton's Encyclopedia (1910)
a genus of plants half way between daisies and sunflowers. There are three species in the eastern part of the United States , and at least four in the Rocky Mountain region; but the arnica of the druggist is extracted from a European plant ranging over the mountains and meadows of the continent from Portugal to Scandinavia. It is called mountain arnica, and mountain tobacco. The plant is perennial, with a stem two feet high, few leaves, and a head of dark golden flowers. Tincture of arnica is a sovereign liniment for bruises and was given formerly as a remedy in cases of paralysis and typhoid fever. See Medicine 2026 Editor's Note: Arnica became one of the most popular of all herbal remedies: creams and gels for bruises and sore muscles line pharmacy shelves, and homeopathic arnica pills are a staple of alternative medicine — though evidence for the ultra-dilute pills is thin, and the raw plant is toxic if swallowed. (Ed: BR 2026-07-20)