214 LEGUMINOS^. 



year 1746, when it was introduced into the London Pharmacopoeia 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 sap-wood are chipped off, the stems 

 cut into logs about three feet long, and the red heart-wood alone 

 exported. By exposure to air and moisture, the wood acquires exter- 

 nally 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 medul- 

 lary 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 polj^gonal 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 {lih^iform) 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 perpen- 

 dicularly. No regular arrangement of the rays is obvious in a longi- 

 tudinal 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. 



Chemical Composition — Logwood was submitted to analysis by 

 Chevreul as early as the year 1810,^ since which period all contribu- 

 tions to a knowledge of the drug refer exclusively to its colouring 

 principle Hcematoxylin, which Chevreul obtained in a crystallized 

 state and called Hematine. The very interesting properties of this 

 substance have been chiefly examined by Erdmann (1842) and by O. 

 Hesse (1858-59). 



Erdmann obtained from logwood 9 to 12 per cent, of crystallized 



hsematoxylin, which he showed to have the formula C^H^O''. In a 



pure state it is colourless, crystallizing with 1 or with 3 equivalents of 



water, and is readily soluble in hot water or in alcohol, but sparingly 



1 Annals tie Chimie, Ixxxi. (1812) 128. 



