SENNA, a popular purgative, consisting of the leaves of two species of Cassia (natural order Leguminosae), viz. C. acutifolia and C. angustifolia. These are small shrubs about 2ft. high, with numerous lanceolate leaflets arranged pinnately on a main stalk with no terminal leaflet ; the yellow flowers are borne in long stalked racemes in the leaf-axils, and are succeeded by broad flat tish pods about gin. long. C. acutifolia is a native of many districts of Nubia, but is grown also in Timbuctoo and Sokoto. The leaflets are collected twice a year, dried by exposure to the sun, packed in large bags made of palm leaves, conveyed by camels to Assouan and Darao and thence to Cairo and Alexandria, or by ship by way of Massowah and Suakim. The leaflets form the Alexandrian senna of commerce. C. angustifolia affords the Bombay, East Indian, Arabian or Mecca senna of commerce. This plant grows wild in the neighbourhood of Yemen and Hadramaut in the south of Arabia, in Somaliland, and in Sind and the Punjab in India. It is also cultivated in the extreme south of India, and there grows larger leaves, which are known in commerce as Tinnevelly senna. American senna is Cassia marilandica.
The British Pharmacopoeia recognizes both Senna Alexandrina and Senna Indica. The active ingredient is cathartic acid, a sul phur containing glucoside of complex formula which is combined with calcium and magnesium to form soluble salts. Cathartic acid
can easily be decomposed into glucose and cathartogenic acid.
The leaves contain at least two other glucosides, sennapicrin and sennacrol, but as these are insoluble in water, they are not con tained in most of the preparations of senna. Senna also contains a little chrysophanic acid.
Of the numerous pharmacopoeial preparations three must be mentioned. The confectio sennae, an admirable laxative for chil dren, contains senna, coriander fruit, figs, tamarind, cassia, pulp, prunes, extract of liquorice, sugar and water. When coated with chocolate it is known as Tamar Indien. The pulvis glycerhizae composites contains two parts of senna in twelve, the other ingre dients being unimportant. A third preparation, rarely employed nowadays, is the nauseous "black draught," once in high favour. It is known as the mistura sennae composita, and contains sulphate of magnesium, liquorice, cardamoms, aromatic spirit of ammonia and infusion of senna.
Senna stimulates the muscular coat of the bowel, the colon being more particularly affected. As some congestion of the rec tum is thereby produced, senna is contra-indicated whenever haemorrhoids are present. The drug has the advantage of not producing subsequent constipation.