Because of their narcotic properties, utilized clinically in the treatment of diseased conditions, the following drugs are included in this subdivision of Narcotics. The most important are belladonna, hyoscyamus, and stramonium. They belong to one family of plants, the Solanacea, and contain active principles - alkaloids -that are very closely related. On account of their characteristic action on the pupil, these drugs are called mydriatics. These active principles, moreover, are confined closely to this family. These alkaloids all contain a tropin nucleus, which is a modified pyridine (a piperidine) to which acid groups are attached.

The tropin base is of particular interest as a starting-point from which these alkaloids can be synthetically constructed. Hyoscy-amine is thought to be isomeric with atropine. Hyoscine (scopolamine) is closely related, but probably differs slightly. The composition of these and other related alkaloids is still in dispute. (Some of these are Duboisine, Mandragorine, Daturine, Atropamine, Belladonnine, Bellatropine, Atroseine, etc.).

The different plants of this group are: Atropa Belladonna, Hyoscyamus niger, Datura Stramonium, Datura alba, Atropa man-dragora, Scopola carniolica, Scopola japonica, Duboisia myoporoides, and Anisodus luridus. Only the more important will be here considered.