TRAGACANTH, familiarly termed Gum dragon, is the produce of several species of the genus Astragalus. [AATRAOALII8, in NAT. HIST. Div.] The A. rents (Olivier,) a native of the north of Persia, Armenia, and Asia Minor, yields the greater part of what is used in Europe. Persia supplies it likewise to India, Baghdad, and Basrah. A. yummifer (LabilL) yields some of the white ere. tints, Lamarck (Tragacantha Cretica incana, Tournefort), yields it sparingly ; while, according to Sibthorp (` Prod. Fl. Green; iL 90), tho tragacanth ,which is used in Italy is obtained in Greece from the A. aristatus (Villara), and which, according to Sibthorp, yields the trisgasianth of Diescoricles. The A. tragatantha (var. a. Linn.), the A. Maarilicasis (Lamarck et Dec.), long reputed to be the source of tra gacanth, yields no concrete gum, but merely a gummy juice, which is used in confectionary. The A. Dicksamii (a name substituted by Dr. Hoyle for A. strobillferas of Lindley) yields the reddish-coloured tragicantli In the hot months of July and August, particularly after a dewy or a cloudy night, the branches of A. rents are found encrusted with tragricanth. It is not procured by artificial incisions, but exudes spontaneously from natural clefts in the bark, or from punctures wade by insects, or more probably by a anbepidermal fungus, like the tonna spora crocea, as the shrubs from which the juice exudes are always in an unhealthy state, or ready to perish. (Decandolle, ' Phys. Veg.,' p. 174.) Iu commerce tragacanth occur, in two forms, termed vermiform, and flake or cake tragacanth. The former, called also Mecca fragaranth, is not frequent in this country. It is mostly in small twisted thread like pieces, seldom in flat or bandlike portions, of a variable size, of a whitish colour. The larger irregular pieces often run together, and are of a yellow or yellowish-brown colour. White worm-like pieces are selected and sold as vermicelli. Flake or Smyrna tragacanth occurs in tolerably large, broad, thin pieces, with concentric elevations or lines, seldom of a filiform shape : colour whitish. Both sorts are hard, yet
somewhat soft and even flexible before breaking; fracture dull and splintery. It is with difficulty reduced to powder, except in winter, or in a heated mortar. It is devoid of taste and smelt It swells in the month, and is lubricous. Fine tragacanth is not rendered blue by iodine, but the Marra tragacanth, is affected by it, as well as an artificial substance prepared by boiling starch, which. hurt article, called traga cantin, does not swell in water. Kutera gum, the produce of a species of cochlospermum and sterculia, which is sometimes mixed with or sub stituted for genuine tragacanth, is not affected by tincture of iodine. It always occurs in stalactite-like pieces, and consisting almost entirely of baasorin, is scarcely soluble in water. [Gum.] Tragacanth approximates more to starch than common gum, than which it is more nourishing, but less digestible. Tmgacanth is to be preferred to gum-arabic to form a mucilage, as one part will inspissate fifty parts of water. It is better to allow pieces of tragacanth slowly to dissolve in cold water than to use the powder with boiling water. Both the mucilage and powder are used to suspend heavy powders in water; also to make lozenges and pills. For eleetuaries it is improper, as it renders them slimy on keeping. As a demulcent, or means of sheathing the Lances and intestines, it is preferable to gum-arabie. its insolubility rendering it a more efficient protection to the mucous membrane against either acrid poisons or unhealthy secretions. Thus in India, tragacanth boiled in rice-water is advantageously administered in dysentery and bloody fluxes. Externally, a thick mucilage of tra gacanth is a good application to burns, to exclude the air.