This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Anchusa, Alcanna, Pharm. Edinb. An-chusa floribus puniceis C. B. Anchusa tinctoria Linn. Alkanet: a rough hairy perennial plant, with unbranched procumbent stalks; of the buglofs kind, and differing from the common buglofles chiefly in the red colour of its roots. It grows wild about Montpelier and in the eastern countries, and is cultivated in some of our gardens; but the roots, produced in this climate, are paler coloured than those which we receive from abroad.
The roots of anchusa, when in perfection, are externally of a deep, purplish red colour. The red cortical part, separated from the whitish woody pith, imparts a fine deep red to oils, wax, and all unctuous substances, and to rectified spirit of wine. To water, it gives only a dull brownish hue. The spirituous tincture, on being infpiffated to the consistence of an extract, changes its fine red to a dark brown. In these general properties, the deep and pale roots agree with one another, and differ from all the reft of the red drugs we know of: it is not, therefore, probable, that the deep colour of the foreign roots is owing, as some have fuppofed, to the introduction of an extraneous tincture.
Alkanet root has little or no smell, and scarcely any taste: extracts made from it, by water and by spirit, are bitterish and roughish, but in too low a degree to be regarded as medicines. Its chief use is for colouring oils, plasters, lip-salves, etc. which receive a fine deep red from one fortieth their weight of the root: the consistent unctuous materials are for this purpose to be liquefied in the heat of a water bath, the powdered anchusa added, the mixture stirred now and then, till sufficiently coloured, and then strained through a linen cloth.