[560] See Casper’s Viertelj., 1844; Keber, Preuss. Vereinszeitg. 1846; Boström, Ber. d. Phys. Med. Soc., Erlangen, 1880; Schauenstein, “Giftige Schwämme” in Maschka’s Handbuch, &c.
DIVISION II.—GLUCOSIDES.
I.—Digitalis Group.
§ 526. The Digitalis purpurea, or foxglove, is a plant extremely common in most parts of England, and poisoning may occur from the accidental use of the root, leaves, or seeds. The seeds are very small and pitted; they weigh 1126 to a grain (Guy), are of a light brown colour, and in form somewhat egg-shaped. The leaves are large, ovate, crenate, narrowed at the base, rugous, veined, and downy, especially on the under surface. Their colour is a dull green, and they have a faint odour and a bitter, nauseous taste. The leaf is best examined in section. Its epidermis, when fresh, is seen to consist of transparent, hexagonal, colourless cells, beneath which, either singly or in groups, there are round cells of a magenta tint, and beneath these again a layer of columnar cells, and near the lower surface a loose parenchyma. The hairs are simple, appearing scantily on the upper, but profusely on the lower, surface; each is composed of from four to five joints or cells, and has at its base a magenta-coloured cell. The small leaves just below the seed-case, and the latter itself, are studded with glandular hairs. The root consists of numerous long slender fibres.
§ 527. Chemical Composition.—It is now generally accepted that there exist in the foxglove, at least, four distinct principles—digitalin, digitonin, digitoxin, and digitalein. Besides these there are several others of more or less definite composition, which are all closely related, and may be derived from a complex glucoside by successive removals of hydrogen in the form of water.