Senna is the dried leaflets of several species of Cassia, various preparations of which are used in medicine as purgatives. Two sorts are recognised in the British Pharmacopœia—viz. Alexandrian senna and Tinnively senna. The Alexandrian senna leaves are chiefly obtained from Cassia acutifolia, while the Tinnively senna leaves are yielded by Cassia angustifolia. Alexandrian senna is chiefly grown in Nubia and Upper Egypt, and is imported in large bales from Alexandria. It is often adulterated largely with the flowers, pods, and leaves of Sole no st c m a Argel. Tinnively or East Indian senna resembles Alexandrian senna in odour and taste. The leaflets are, however, larger and finer, 'about 2 inches long, lanceo- late, acute, unequally oblique at the base, flexible, entire, green, without any admixture.' The rounder leaves of the C. obovata are also used in medicine, and are sometimes mixed with the other kinds.
The active principle in senna is a glucoside, which has been named cathartic acid, and which is closely allied to chrysarobin and the purgative principle in rhubarb; there are also other substances which impart to senna its peculiar odour and taste, as well as a variety of sugar. The different pharmaceutical preparations of senna act as moderately active cathartics, but tend to cause griping. To obviate this, and to disguise the nauseous taste of the drug, they are all made up with a number of carminative and flavouring substances. The active principles in senna are excreted in the urine, which is coloured a deep yellow, and by the milk, which is rendered purgative. The officinal preparations comprise the confec-tion of senna (dose 60 to 120 grains), the infusion of senna (dose 1 to 2 fluid oz.), the syrup of senna (dose 1 to 4 fluid drachms), the tincture of senna (dose 2 to 8 fluid drachms), and the compound mixture of senna or 'black draught' (dose 1 to 1½ fluid oz.). Compound liquorice powder consists largely of senna. The dose of senna itself is 10 to 30 grains.
BLADDER SENNA (Colutea) is a genus of shrubs of the natural order Leguminosæ, sub-order Papilionaceæ, having pinnated leaves, red or yellow flowers, and remarkably inflated pods, whence the English name. One species (C. arborescens) is common in shrubberies in Britain. It is a native of the south of Europe, and is found on the ascent of the crater of Mount Vesuvius—almost the only plant that exists there.