The root though hard is easily shaved with a knife, some pieces giving the impression when cut of a waxy, rather than of a woody and fibrous substance. The taste is bitter, well marked but not persistent. The drug has no particular odour. Its aqueous decoction is turned inky bluish-black by tincture of iodine.
The aerial stems especially differ by enclosing a small but well-defined pith.
Microscopic Structure—The most interesting character consists in the arrangement rather than in the peculiarity of the tissues composing this drug. The wavy light-coloured lines already mentioned are built up partly of sclerenchymatous cells. The other portions of the parenchyme are loaded with large starch granules, which are much less abundant in the stem.
Chemical Composition—From the examination of this drug made by one of us in 1869,[127] it was shown that the bitter principle is the same as that discovered in 1839 by Wiggers in the drug hereafter described as Common False Pareira Brava, and named by him Pelosine. It was further pointed out that this body possesses the chemical properties of the Bibirine of Greenheart bark and of the Buxine obtained by Walz from the bark of Buxus sempervirens L. It was also obtained on the same occasion (1869) from the stems and roots of Cissampelos Pareira L. collected in Jamaica; but from both drugs in the very small proportion of about ½ per cent.
Whether to Buxine (for by this name rather than Pelosine it should be designated) is due the medicinal power of the drug may well be doubted. No further chemical examination of true Pareira Brava has been made.
Uses—The medicine is prescribed in chronic catarrhal affections of the bladder and in calculus. From its extensive use in Brazil[128] it seems deserving of trial in other complaints. Helvetius used to give it in substance, which in 5-grain doses was taken in infusion made with boiling water from the powdered root and not strained.
Substitutes—We have already pointed out how the name Pareira Brava has been applied to several other drugs than that described in the foregoing pages. We shall now briefly notice the more important.
1. Stems and roots of Cissampelos Pareira L.—Owing to the difficulty of obtaining good Pareira Brava in the London market, although this plant is very widely diffused over all the tropical regions of both hemispheres, the firm of which one of us was formerly a member (Messrs. Allen and Hanburys, Plough Court, Lombard Street) caused to be collected in Jamaica, under the superintendence of Mr. N. Wilson, of the Bath Botanical Gardens, the stems and root of Cissampelos Pareira L., of which it imported in 1866-67-68 about 300 lb. It was found impracticable to obtain the root per se; and the greater bulk of the drug consisted of long cylindrical stems,[129] many of which had been decumbent and had thrown out rootlets at the joints. They had very much the aspect of the climbing stems of Clematis vitalba L., and varied from the thickness of a quill to that of the forefinger, seldom attaining the diameter of an inch. The stems have a light brown bark marked longitudinally with shallow furrows and wrinkles, which sometimes take a spiral direction. Knots one to three feet apart, sometimes throwing out a branch, also occur. The root is rather darker in colour, but not very different in structure from the stem.
The fracture of the stem is coarse and fibrous. The transverse section, whether of stem or root, shows a thickish, corky bark surrounding a light brown wood composed of a number of converging wedges (10 to 20) of very porous structure, separated by narrow medullary rays. There are no concentric layers of wood,[130] nor is the arrangement of the wedges oblique as in many other stems of the order. The drug is inodorous, but has a very bitter taste without sweetness or astringency.
2. Common False Pareira Brava—Under this name we designate the drug which for many years past has been the ordinary Pareira Brava of the shops, and regarded until lately as derived from Cissampelos Pareira L. We have long endeavoured to ascertain, through correspondents in Brazil, from what plant it is derived, but without success. We only know that it belongs to the order Menispermaceæ.