Botanical Origin—Hæmatoxylon campechianum L., a spreading tree[821] of moderate size, seldom exceeding 40 feet in height, native of the bay of Campeachy, Honduras and other parts of Central America. It was introduced into Jamaica by Dr. Barham[822] in 1715, and is now completely naturalized in that and other of the West Indian Islands.
History—Hernan Cortes in his letter to the Emperor Charles V., giving an account of his expedition to Honduras in 1525,[823] refers to the Indian towns of Xiculango and Tabasco as carrying on a trade in cacao, cotton cloth, and colours for dyeing,—in which last phrase there may be an allusion to logwood. We have sought for some more definite notice of the wood in the Historia de las Indias of Oviedo,[824] the first chronicler of America, but without much success.
Yet the wood must have been introduced into England in the latter half of the 16th century, for, in 1581, an Act of Parliament[825] was passed, abolishing its use and ordering that any found should be forfeited and burned. In this Act the obnoxious dye is described as “a certain kind of ware or stuff called Logwood alias Blockwood ... of late years ... brought into this realm of England.” The object of this measure was to protect the public against the bad work of the dyers, who, it seems, were unable at that period to obtain durable colours by the use of logwood. Eighty years later the art of dyeing had so far improved that logwood was again permitted,[826] the colours produced by it being declared as lasting and serviceable as those made by any other sort of dyewood whatsoever.
The wood is mentioned by De Laet (1633) as deriving its name from the town of Campeachy, whence, says he, it is brought in great plenty to Europe.[827]
As a medicine, logwood was not employed until shortly before the year 1746, when it was introduced into the London Pharmacopœia under the name of Lignum tinctile Campechense.
Description—The tree is fit to be felled when about ten years old; the dark bark and the yellowish sapwood are chipped off, the stems cut into logs about three feet long, and the red heartwood alone exported. By exposure to air and moisture, the wood acquires externally a blackish-red colour; internally it remains brownish red. It splits well, although of a rather dense and tough texture.
The transverse section of a piece of logwood exhibits to the naked eye a series of very narrow concentric zones, formed by comparatively large pores, and of small parenchymatous circles separated by the larger and darker rings of the proper woody tissue. The numerous medullary rays are visible only by means of a lens. The wood has a pleasant odour.
For use in pharmacy, logwood is always purchased in the form of chips, which are produced by the aid of powerful machinery. The chips have a feeble, seaweed-like odour, and a slightly sweet, astringent taste, better perceived in a watery decoction than by chewing the dry wood, which however quickly imparts to the saliva its brilliant colour.
Microscopic Structure—Under a high magnifying power, the concentric zones are seen to run not quite regularly round the centre, but in a somewhat undulating manner, because they do not correspond, as in our indigenous woods, to regular periods of annual growth. The vascular bundles contain only a few vessels, and are transversely united by small lighter parenchymatous bands. The latter are made up of large, cubic, elongated or polygonal cells, each loaded with a crystal of oxalate of calcium. The large punctuated vessels having frequently 150 mkm. diameter, are surrounded by this woody parenchyme, while the prevailing tissue of the wood is composed of densely packed prosenchyme, consisting of long cylindrical cells (libriform) with thick, dark red-brown walls having small pores.
The medullary rays are of the usual structural character, running transversely in one to three straight rows; in a longitudinal section, the single rays show from 4 to 40 rows succeeding each other perpendicularly. No regular arrangement of the rays is obvious in a longitudinal section made in a tangential direction. The colouring matter is chiefly contained in the walls of the ligneous tissue and the vessels, and sometimes occurs in crystals of a greenish hue within the latter, or in clefts of the wood.