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Encyclopedia Britannica - Main :: GRA-GUI |
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GUAIACUM , a genus of trees of the natural order Zygophyllaceae. The guaiacum or lignum-vitae tree (Ger. Guajakbaum, Franzosenbaum, Pockenholzbaum; Fr. Gayac, Gayac), G. officinale, is a native of the West Indies and the north coast of South America, where it attains a height of 20 to 30 ft. Its branches are numerous, flexuous and knotted; the leaves opposite and pinnate, with caducous (falling early) stipules, and entire, glabrous, obovate or oval leaflets, arranged in 2 or, more rarely, 3 pairs; the flowers
pale -blue petals three times the length of the sepals, to stamens, and a 2-celled superior ovary. The fruit is about 4 in. long, with a leathery pericarp, and contains in each of its two cells a single seed (see fig.). G. sanctum grows in the Bahamas and Cuba, and at Key West in Florida. It is distinguished from G. officinale by its smaller and narrow leaflets, which are in 4 to 5 pairs, by its shorter and glabrous sepals, and 5-celled and 5-winged fruit. G. arhoreum, the guaiacum tree of Colombia, is found in the valley of the Magdalena up to altitudes 800 metres (2625 ft.) above sea-level, and reaches considerable dimensions. Its wood
flowers
The lignum vitae of commerce, so named on account of its high repute as a medicinal agent in past times, when also it was known as lignum sanctum and lignum Indicum, lignum guaycanum, or simply guayacan, is procured from G. officinale, and in smaller amount from G. sanctum. It is exported in large logs or blocks, generally divested of bark, and presents in transverse section very slightly marked concentric rings of growth, and scarcely any traces of pith; with the aid of a magnifying glass the medullary rays are seen to be equidistant and very numerous. The outer wood
pale yellow hue, and devoid of resin; the inner, the heartwood or duramen, which is by far the larger proportion, is of a dark greenish-brown, contains in its pores 26% of resin, and has a specific gravity of 1.333, and therefore sinks in water on which the alburnum floats. Owing to the diagonal and oblique arrangement of the successive layers of its fibres, the wood cannot be split; and on account of its hardness, density and durability it is much valued for the manufacture of ships' pulleys, rulers, skittle-balls, mallets and other articles.Chips or turnings of the heartwood of G. officinale (guaiaci lignum) are employed in the preparation of the liquor sarsae compositus concentratus of British pharmacy. They may be recognized by being either yellow of greenish-brown in colour, and by turning bluish-green when treated with nitric acid, or when heated with corrosive sublimate, and green with solution From Bentley & Trimen's Medicinal Plants, by permission of J. & A. Churchill. Guaiacum or Lignum Vitae,Guaiacum officinale shoot-bearing leaves and flowers. i, Fruit; 2, Vertical section of fruit, showing the solitary pendulous seed in each chamber. All about t natural size. of chloride of lime. They are occasionally adulterated with boxwood shavings. Lignum vitae is imported chiefly from St Domingo, the Bahamas and Jamaica. The bark was formerly used in medicine; it contains much calcium oxalate, and yields on incineration 23 % of ash. Guaiacum resin, the guaiaci resina of pharmacopoeias, is obtained from the wood as an exudation from natural fissures or from incisions; by heating billets about 3 ft. in length, bored to permit of the outflow of the resin; or by boiling chips and raspings in water to which salt has been added to raise the temperature of ebullition. It occurs in rounded or oval tears, commonly coated with a greyish-green dust, and supposed to be the produce of G. sanctum, or in large brownish or greenish-brown masses, translucent at the edges; fuses at 85 C.; is brittle, and has a vitreous fracture, and a slightly balsamic odour, increased by pulverization and by heat; and is at first tasteless when chewed, but produces subsequently a sense of heat in the throat. It is readily soluble in alcohol, ether, chloroform, creosote, oil of cloves and solutions of caustic alkalies; and its solution gives a blue colour with gluten, raw potato
chief
Guaiacum wood was first introduced into Europe by the Spaniards in 1508, and Nicolaus Poll, writing in 1517 (see Luisinus, De morbo gallico, p. 210, Ven., 1566), states that some three thousand persons in Spain had already been restored to health by it. The virtues of the resin, however, were not known until a later period, and in Thomas
GUALEGUAYCHU 647 use of salt was specially to be avoided. A decoction of 1 lb of guaiacum was held to be sufficient for the four first days of the treatment. The earlier opinions as to the efficacy of guaiacum came to be much modified in the course of time, and Dr Pearson (Observations on the Effects of Various Articles of the Mat. Med. in the Cure of Lues Venerea, c. i., 2nd ed., 1807) says:" I never saw one single instance in which the powers of this medicine eradicated the venereal virus." He found its beneficial effects to be most marked in cases of secondary symptoms. Guaiacum resin is given medicinally in doses of 5-15 grains. Its important preparations in the British Pharmacopoeia are the mistura guiaci (dose a-i oz.), the ammoniated tincture of guaiacum (dose 1-1 drachm), in which the resin is dissolved by means of ammonia, and the trochiscus or lozenge , containing 3 grains of the resin. This lozenge is undoubtedly of value when given early in cases of sore throat, especially of rheumatic origin. Powdered guaiacum is also used.Guaiacum resin differs pharmacologically from other resins in being less irritant, so that it is absorbed from the bowel and exerts remote stimulant actions, notably upon the skin and kidneys. It affects the bronchi but slightly, since it contains no volatile oil. The drug is useful both in acute and chronic sore throat, the mixture, according to Sir Lauder Brunton, being more effective than the tincture. The aperient action, which it exerts less markedly than other members of its class, renders it useful in the treatment of chronic constipation. Sir Alfred Garrod has urged the claims of this drug in the treatment of chronic gout. Both in this disease and in other forms of chronic arthritis guaiacum may be given in combination with iodides, which it often enables the patient to tolerate. Guaiacum is not now used in the treatment of syphilis. The tincture of guaiacum is universally used as a test for the presence of blood, or rather of haemoglobin, the red colouring matter of the blood, in urine or other secretions. This test was first suggested by Dr John Day of Geelong, Australia. A single drop of the tincture should be added to, say, an inch of urine in a test-tube. The resin is at once precipitated, yielding a milky fluid. If " ozonic ether "an ethereal solution of hydrogen peroxidebe now poured gently into the test-tube, a deep blue coloration is produced along the line of contact if haemoglobin be present. The reaction is due to the oxidation of the resin by the peroxide of hydrogensuch oxidation occurring only if haemoglobin be present to act as an oxygen- carrier .End of Article: GUAIACUM If you wish, you can link directly to this article.
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