Guaiacum , a name applied to both the wood and a resinous substance from the guaiacum officinale, of the natural order zygophyllacecoe. The tree grows in the West Indies and on the mainland opposite. The trunk is sometimes 5 ft. in circumference. The wood, commonly known as lignum vita?, is remarkably heavy and hard, and is much used for the sheaves of tackle blocks, for nine-pin balls, and other purposes requiring strength and resistance to wear. It possesses medicinal properties, as does also the concrete juice or resin. Both are kept by druggists, the wood in the form of chips or shavings, and the resin in lumps or powder under the name of gum guaiacum.
The wood contains about 20 per cent. of resin, and 0.8 of a bitter pungent extractive. The resin, which is the more active medicine, is obtained either by spontaneous exudations from incisions made into the tree, or by heating blocks of the wood, in which auger holes have been bored in the centre in the direction of the grain, and collecting the juice as it flows out through the holes; also by boiling the chips and sawdust of the wood in salt water, and skimming off the matter which rises to the surface. This is the form in which it is usually met with. More rarely it is found in rounded or oval masses, about the size of a walnut, called "guaiac in tears;" this is said to be produced by G. sanctum, another West Indian species, which is also found in southern Florida. The irregular-shaped pieces brought to the United States are of a dark olive color without and reddish brown within, diversified with various shades; they have a slight fragrant odor, and a pungent acrid taste after being held in the mouth a short time. The ! pure substance is entirely soluble in alcohol, ether, alkaline solutions, and sulphuric acid. It is adulterated with common rosin, from which it may be distinguished by the solubility of the latter in turpentine.
The powder and the tincture become green on exposure to light. The tincture affords blue, green, and brown precipitates with the mineral acids, and a blue color with oxidizing agents. If tincture of guaiacum is applied to the freshly cut surfaces of many vegetables, or added to infusions of the green plants, it gives a bright blue color, which is due to the presence of oxygen in the nascent form or of ozone, for the presence of which guaiacum is a useful test. The color is most marked at those portions of the plant where growth is taking place most rapidly. Similar reactions afforded by guaiacum with blood, pus and mucus, have been made available for physiological and medico-legal purposes. Guaiacum is administered in many complaints, especially chronic rheumatism. It promotes various secretions, especially those of the skin and kidneys, but diminishes excessive secretion of mucous surfaces. In large doses it purges. Febrile affections and irritated conditions of the gastro-intestinal membrane contraindicate its use. When a rheumatic diathesis underlies bronchitis, leucor-rhoea, dysmenorrhoea, amenorrhoea, or syphilis, guaiacum often yields an unequivocal benefit. It is much less used now than formerly.
It may be given in the form of decoction of the wood, tincture of the resin, or of the resin in substance. The dose of the latter is from 10 to 30 grs.; of the tincture, about a teaspoonful.