Microscopic Characters—The suberous coat is made up of numerous rows of tabular cells, the outermost having their exterior walls much thickened. The mesophlœum exhibits the usual tissue, containing starch, chlorophyll, essential oil, crystals of oxalate of calcium, and a brown colouring matter. The latter assumes a dark bluish coloration on addition of a persalt of iron. In the inner portion of that layer ramified laticiferous vessels are also present. The liber consists of parenchyme and of fibrous bundles, intersected by small medullary rays. On the transverse section, the fibrous bundles show a wedge-shaped outline; they are for the most part built up, not of true liber-fibres, but of cylindrical cells having their transverse walls perforated sieve-like (vasa cribriformia). The contents of the parenchymatous part of the liber are the same as in the mesophlœum; as to the oxalate of calcium, the variety of its crystals is remarkable.[2089]
Chemical Composition—Cascarilla contains a volatile oil, which it yields to the extent of 1·1 per cent. According to Völckel (1840), it is a mixture of at least two oils, the more volatile of which is probably free from oxygen. Gladstone (1872) assigns to the hydrocarbon of cascarilla oil the composition of oil of turpentine. By examining the oil optically we found it to have a weak rotatory power—some samples deviated to the right, some to the left. The resin, in which cascarilla is rich, has not yet been examined more exactly.
The bitter principle was isolated in 1845 by Duval, and called Cascarillin. C. and E. Mylius (1873) have obtained it from a deposit in the officinal extract, in microscopic prisms readily soluble in ether or hot alcohol, very sparingly in water, chloroform or spirit of wine. It melts at 205° C., is not volatile, nor a glucoside. Its composition answers to the formula C₁₂H₁₈O₄.
Commerce—The bark is shipped from Nassau, the chief town of New Providence (Bahamas), and is usually packed in sacks. The quantity imported into the United Kingdom in 1870 was 12,261 cwt., valued at £16,482. The exports from the Bahamas were 676 cwt. in 1875, and 1,093 cwt. in 1876.
Uses—Cascarilla is prescribed as a tonic, usually in the form of a tincture or infusion.
Adulteration—A spurious cascarilla bark has lately been noticed in the London market; it was imported from the Bahamas mixed with the genuine, to which it bears a close similarity. The quills of it resemble the larger quills of cascarilla; though covered with a lichen, the latter has not the silvery whiteness of the Verrucaria of cascarilla. The spurious bark has a suberous coat that does not split off; its inner surface is pinkish-brown, and distinctly striated longitudinally. In microscopic structure the bark may be said to resemble cascarilla and still more copalchi. But it is at once distinguishable by its numerous roundish groups of sclerenchymatous cells, which become very evident when thin sections are moistened with ammonia, and then with solution of iodine in iodide of potassium. The bark has an astringent taste, without bitterness or aroma; its tincture is not rendered milky by addition of water, but is darkened by ferric chloride,—in these respects differing from a tincture of cascarilla. Mr. Holmes[2090] suggests that this spurious cascarilla is probably the bark of Croton lucidus L.
Copalchi Bark; Quina blanca of the Mexicans.
This drug is derived from Croton niveus[2091] Jacquin (C. Pseudo-China Schlechtendal), a shrub growing 10 feet high, native of the West Indian Islands, Mexico, Central America, New Granada and Venezuela. It has occasionally been imported into Europe, in quills a foot or two in length, much stouter and thicker than those of cascarilla, to which in odour and taste it nearly approximates. The bark has a thin, greyish, papery suberous layer, which when removed shows the surface marked with minute transverse pits, like the lines made by a file; it has a short fracture.[2092]
Copalchi bark was examined by J. Eliot Howard,[2093] and found to contain a minute proportion of a bitter alkaloid soluble in ether, which resembled quinine in yielding a deep green colour when treated with chlorine and ammonia, though it did not afford any characteristic compound with iodine. Mauch,[2094] who also analysed the bark, could not obtain from it any organic base. He extracted by distillation the essential oil, which he found to consist of a hydrocarbon and an organic acid,—the latter not examined; he likewise got from the bark an uncrystallizable bitter principle, which proved to be not a glucoside.