Uses—Logwood in the form of decoction is occasionally administered in chronic diarrhœa, and especially in the diarrhœa of children. Cases have occurred in which its use has been followed by phlebitis. Its employment in the art of dyeing is far more important.
Adulteration—The woods of several species of Cæsalpinia imported under the name of Brazil Wood and used for dyeing red, bear an external resemblance to logwood, with which it is said they are sometimes mixed in the form of chips. They contain a crystallizable colouring principle called Brasilin, C₂₂H₂₀O₇, or, according to Liebermann and Burg (1876), C₁₆H₁₄O₅, which affords with alkalis red and not bluish or purplish solutions, and yields trinitrophenol, C₆H₂(NO₂) 3OH (picric acid), when boiled with nitric acid, while hæmatoxylin yields oxalic acid only. The best source for brasilin is the wood of Cæsalpinia Sappan L., a tree of the East Indies, well known as Bakam, Brazil Wood, Lignum Brasile, Verzino of the Italians, an important object of commerce during the middle ages.[832]
FOLIA SENNÆ.
Senna Leaves; F. Feuilles de Séné; G. Sennesblätter.
Botanical Origin—The Senna Leaves of commerce are afforded by two species of Cassia[833] belonging to that section of the genus which is distinguished by having leaves without glands, axillary racemes elongating as inflorescence advances, membranaceous bracts which in the young raceme conceal the flower buds but drop off during flowering, and a short, broad, flat legume.
The senna plants are low perennial bushy shrubs, 2 to 4 feet high, having pari-pinnate leaves with leaflets unequal at the base, and yellow flowers. The pods contain 6 or more seeds in each, suspended on alternate valves by long capillary funicles. These run towards the pointed end of the seed, but are curved at their attachment to the hilum just below. The seeds are compressed and of an obovate-cuneate or oblong form, beaked at the narrower end.[834]
The species in question are the following:—
1. Cassia acutifolia Delile[835]—a shrub about 2 feet high, with pale subterate or obtusely angled, erect or ascending branches, occasionally slightly zigzag above, glabrous at least below. Leaves usually 4-5-jugate; leaflets oval or lanceolate, acute, mucronate, usually more or less distinctly puberulous or at length glabrous, pale or subglaucous at least beneath, subsessile. Stipules subulate, spreading or reflexed, 1-2 lines long. Racemes axilliary, erect, rather laxly many-flowered, usually considerably exceeding the subtending leaf. Bracts membranous, ovate or obovate, caducous. Pedicels at length 2-3 lines. Sepals obtuse, membranous. Two of the anterior anthers much exceeding the rest of the fertile stamens. Legume flat, very broadly oblong, but slightly curved upwards, obliquely stipitate, broadly rounded at the extremity with a minute or obsolete mucro indicating the position of the style on the upper edge; 1½-2¼ inches long, ¾-1 inch broad; valves chartaceous, obsoletely or thinly puberulous, faintly transverse-veined, unappendaged. Seeds obovate-cuneate, compressed; cotyledons plane, extending the large diameter of the seed in transverse section.[836]
The plant is a native of many districts of Nubia (as Sukkot, Mahas, Dongola, Berber), Kordofan and Sennaar; grows also in Timbuktu and Sokoto, and is the source of Alexandrian Senna.
2. C. angustifolia Vahl[837]—This species is closely related to the preceding, the general description of which is applicable to it with the following exceptions. In the present plant the leaflets, which are usually 5-8-jugate, are narrower, being oval-lanceolate, tapering from the middle towards the apex; they are larger, being from one to nearly 2 inches long, and are either quite glabrous or furnished with a very scanty pubescence. The legume is narrower (7-8 lines broad), with the base of the style distinctly prominent on its upper edge.