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EUCALYPTUS
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EUCALYPTUS , a large genus of trees of the natural See also:order Myrtaceae, indigenous, with a few exceptions, to See also:Australia and See also:Tasmania. In Australia the Eucalypti are commonly called
See also:gum-trees " or " stringy-bark trees," from their gummy or resinous products, or fibrous bark. The genus, from the See also:evidence of See also:leaf-remains, appears to have been represented by several See also:species in See also:Eocene times. The leaves are leathery in texture, hang obliquely or vertically, and are studded with glands which contain a fragrant volatile oil. The petals cohere to See also:form a cap' which is discarded when the See also:flower expands. The See also:fruit is surrounded by a woody See also:cup-shaped receptacle and contains very numerous See also:minute seeds. The Eucalypti are rapid in growth, and many species are of See also:great height, E. amygdalina, the tallest known See also:tree, attaining to as much as 48o ft., exceeding in height the Californian big-tree (See also:Sequoia gigantea), with a See also:diameter of 81 ft. E. globules, so called from the rounded form of its caps like corolla, is the See also:blue gum tree of See also:Victoria and Tasmania. The leaves of trees from three to five years of See also:age are large, sessile and of a See also:glaucous-See also: Since 1854 it has been successfully introduced into the See also:south of See also:Europe, See also:Algeria, See also:Egypt, See also:Tahiti, New See also:Caledonia, See also:Natal and See also:India, and has been extensively planted in See also:California, and, with the See also:object of lessening liability to droughts, along the See also:line of the Central Pacific railway. It would probably thrive in any situation having a mean See also:annual temperature not below 6o° F., but it will not endure a temperature of less than 270 F. Its supposed See also:property of reducing the amount of See also:malaria in marshy districts is attributable to the drainage effected by its roots, rather than to the antiseptic exhalations of its leaves. To the same cause also is ascribed the See also:gradual disappearance of mosquitoes in the neighbourhood of plantations of this tree, as at See also:Lake Fezara, in Algeria. Since about 1870, when the tree was planted in its cloisters, the monastery of St See also:Paolo a la tre See also:Fontana has become habitable throughout the See also:year, although situated in one of the most See also:fever-. stricken districts of the See also:Roman Campagna. An essential oil is obtained by aqueous See also:distillation of the leaves of this and other species of Eucalyptus, which is a colourless or See also:straw-coloured fluid when freshly prepared, with a characteristic odour and See also:taste, of sp. gr. 0.910 to 0.930, and soluble in its own See also:weight of See also:alcohol. This consists of many different bodies, the most important of which is eucalyptol, a volatile oil, which constitutes about 70%. This is the portion of eucalyptus oil which passes over between 3470 and 3510 F., and crystallizes at 30° F. It consists chiefly of a terpene and cymene. Eucalyptus oil also contains, after exposure to the See also:air, a crystallizable See also:resin derived from eucalyptol. The dose of the oil is z to 3 minims. Eucalyptol may be given in similar doses, and is preferable for purposes of inhalation. The oil derived from E. amygdalina contains a large quantity of phellandrene, which forms a crystalline nitrate, and is very irritating when inhaled. The See also:oils from different species of Eucalyptus vary widely in See also:composition. Eucalyptus oil is probably the most powerful antiseptic of its class, especially when it is old, as See also:ozone is formed in it on exposure to air. Internally it has the typical actions of a volatile oil in marked degree. Like See also:quinine, it arrests the normal amoeboid movements of the polymorphonuclear leucocytes, and has a definite antiperiodic See also:action; but it is a very poor substitute for quinine in malaria. In large doses it acts as an irritant to the kidneys, by which it is largely excreted, and as a marked See also:nervous depressant, abolishing the reflex functions of the See also:spinal See also:cord and ultimately arresting respiration by its action on the medullary centre. An emulsion, made by shaking up equal parts of the oil and powdered gum-arabic with See also:water, has been used as a urethral injection, and has also been given internally in drachm doses in pulmonary See also:tuberculosis and other microbic diseases of the lungs and bronchi. The oil has somehow acquired an extraordinary popular reputation in See also:influenza, but there is no evidence to show that it has any marked See also:influence upon this disease or that its use tends to lessen the chances of infection. It has been used as an antiseptic by surgeons, and is an ingredient of " catheter oil," used for sterilizing and lubricating urethral catheters, now that carbolic oil, formerly employed, has been shown to be practically worthless as an antiseptic. Eucalyptus rosirata and other species yield eucalyptus or red gum, which must be distinguished from See also:Botany See also:Bay kino. Red gum is very powerfully astringent and is given internally, in doses of 2 to 5 grains, in cases of See also:diarrhoea and pharyngeal inflammation. It is prepared by the pharmacist in the form of tinctures, insuffiations, syrups, lozenges, &c. Red gum is See also:official in Great See also:Britain. E. globulus, E. resinifera, and other species, yield what is known as Botany Bay kino, an astringent dark-reddish amorphous resin, which is obtained in a semi-fluid See also:state by making incisions in the trunks of the trees. The kino of E. gigantea contains a notable proportion of gum. J. H. See also:Maiden enumerates more than See also:thirty species as kino-yielding. From the leaves and See also:young bark of E. mannif era and E. viminalis is procured Australian See also:manna, a hard, opaque, sweet substance, containing melitose. See also:EUCHARIST On destructive distillation the leaves yield much See also:gas, ro,000 cub. ft. being obtained from one ton. The See also:wood is extensively used in Australia as See also:fuel, and the See also:timber is of remarkable See also:size, strength and durability. Maiden enumerates nearly 70 species as timber-yielding trees including E. amygdalina, the wood of which splits with remarkable facility, E. botryoides, hard, tough and durable and one of the finest timbers for See also:shipbuilding, E. diversicolor or " karri," E. globulus, E. leucoxylon or ironbark, E. marginata or " jarrah " (see JARRAH WOOD), E. obliqua, E. resinifera, E. siderophloia and others. The timber is often very hard, tough and durable, and useful for shipbuilding, See also:building, See also:fencing, planks, &c. The bark of different species of Eucalyptus has been used in See also:paper-making and tanning, and in See also:medicine as a febrifuge.
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