This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Under the name of Belladonna, the British Pharmacopoeia recognizes the leaves of Atropa Belladonna, or deadly nightshade, which in our own are designated as Belladonnae Folium; while in both, the root of the plant is officinal, with the title of Belladonnae Radix. The plant is herbaceous, but perennial, indigenous in Europe, and cultivated in this country, but to no great extent, for medicinal purposes. Though all parts of the plant are active, the leaves only were officinally recognized until the recent revision of the Pharmacopoeias, when the root, which is said to be much more active than the leaves, was adopted.* The fruit, though not specially used in medicine, merits a particular notice, as it is highly poisonous, and has frequently been eaten with fatal effect.
* Hirtz states that the roots are stronger than the leaves in the proportion of five to one. (Ann. de Therap., 1862, p. 22).
The root is a foot or more in length, round, an inch or more in thickness, branched, grayish or brownish-white when fresh, becoming reddish-brown by drying, internally whitish and fleshy, of a faint peculiar odour, and sweetish, slightly bitter, mawkish taste. The leaves, which are often in unequal pairs, upon short footstalks, are from four to six inches long, ovate, pointed, entire upon their edges, of a deep-green colour above and paler below when fresh, of a dusky or brownish-green when dried, and, in the latter state, almost destitute of odour, and of a feeble subacrid taste. The fruit is a berry, at first green, then red, and, when ripe, of a fine glossy blackish-purple colour, about as large as a cherry, with a longitudinal furrow on each side, having the adhering calyx at the base, and containing numerous seeds in a juicy pulp. Its taste is sweetish, but mawkish, and not agreeable. All parts of the plant impart their medicinal properties to water and alcohol.
Active Principle. The ingredient to which belladonna chiefly if not exclusively owes its virtues is a peculiar alkaloid, denominated atropia, which will be specially treated of at the close of this article. Brandes obtained also a peculiar substance called pseudotoxin, and Lubekind supposed that he had detected another alkaloid which he named bella-donnin; but little is known of their properties; and the ordinary existence of the latter may be looked on as doubtful. In relation to the incompatibility between atropia and caustic potassa and soda, even in very weak solution, the same remarks are applicable as were made upon hyoscyamia. (See page 177).