GUARANA, so called from the Guaranis, an aboriginal American tribe, the plant Paullinia sorbilis, Mart., of the natural order Sapinclacece and tribe Sapindece, indigenous to the north and west of Brazil. It has a smooth erect stem; large pinnate alternate leaves, composed of 5 oblong-oval leaflets ; inflorescence in narrow panicles of short-stalked flowers, having 4 or 5 sepals and 4 petals, 8 stamens, and a cylindrical 3-celled ovary ; and fruit ovoid or pyriform, about as large as a grape, and containing usually one seed only, which is shaped like a minute horse-chestnut. What is commonly known as guarana, guarana bread, or Brazilian cocoa, is prepared from the seeds as follows. In October and November, at which time they become ripe, the seeds are removed from their capsules, and sun-dried, so as to admit of the ready removal by hand of the white aril; they are next ground in a stone mortar or deep dish of hard sandstone ; the powder, moistened by the addition of a small quantity of water, or by exposure to the dews, is then made into a paste with a certain proportion of whole or broken seeds, and worked up sometimes into balls, but usually into rolls not unlike German sausages, 5 to 8 inches in length, and 12 to 16 oz. in weight.. After drying by artificial or solar heat, the guarana is packed between broad leaves in sacks or baskets. Thus prepared, it is of extreme hardness, and has a brown hue, a bitter astringent taste, and an odour faintly resembling that of roasted coffee. An inferior kind, softer and of a lighter colour, is manufactured by admixture of cocoa or cassava. Rasped or grated into sugar and water, guarana forms a beverage largely consumed in S. America. Its manufacture, originally confined to the Mauhes Indians, has spread into various parts of Brazil.

The properties of guarana as a nervous stimulant and restorative. are due to the presence of what was described as a new principle, and termed guaranine, by Dr T. Martins, but which was proved by Berthemot and Deschastelus (Join-n. de Harm., vol. xxvi., 1840, p. 518 sq.) to be identical with caffeine or theine, 0,11101i +H20. Of .his alkaloid guarana yields 5.07 per cent., against 2.13 in good black tea, •8 to 1 in coffee beans, and 1.2 in mate or Paraguay tea (Stenhouse, Pharm. J0219'71. xvi. p. 213) ; for medical purposes it may in fact be regarded as "practically a convenient form of impure caffeine" (F. E. Anstie, Braithw. Retrosp., 1873, i. p. 35). Besides this substance, which is stated to exit in it in the form of fermate, guarana yields on analysis the glucoside with tannin, starch, gum, three volatile oils, and an acrid green fixed oil (Fournier, Journ. de Pharm., vol. xxxix., 1861, p. 291). As a medicine, guarana was first described in 1817 by Cadet de Gassicourt, to whom a specimen was sent from Brazil (see Bull. Gen. de Mercy., lii., 1857, p. 497 sq.), in which country it is in popular repute as a stomachic, febrifuge, and aphrodisiac, and more especially as a specific for dysentery and diarrhoea, in which latter disease it is given in very large doses-4 to 8 or 10 grammes (Bull. Gen. de Therap., liii. p. 139). It is said by Martins (Syst. Mat. Med. Veget. Brasiliensis, p. 59, Leipsic, 1843) to diminish fever by its tonic effects on the nerves, to invigorate the stomach and intestines, to restrain excessive mucous discharges, to increase the action of the arteries and heart, and to promote diaphoresis. In migraine, or sick-headaehe, it has oftentimes been found a most serviceable remedy (see inter alia, Brit. Med. Journ., 1872, i. pp. 421 and 426 ; Practitioner, Aug. and Sept. 1873, pp. 100-102, 161-175); and it has been recommended in lumbago when the pain is of a stinging nature (Rawson, Braithw. Betrosp., 1874, ii. p. 33), and in sciatica and blennorrhcea.

See Spix and Martins, R,eise in Brasilien, vol. iii. pp. 1061 and 1098, Munich, 1831 ; Hooker's Journ. of Botany, vol. iii., 1851, pp. 193-4 ; Bentley and Trimen, Medicinal Plants, pt. 4, tab. 67, 1876; and, on the preparation of " Guaranine," Journ. de Pharm., 4th se•., xviii. p. 224. On the "Antagonism between Guaranine and Meconate of Morphia," see J. H. Bennett, Rep. on the Antag. 0/ Medicines, p. 86, 1875. Further bibliographical references will be found in Prof. P. Mantegazza's excellent article, " Del guaranb, nuovo alimento nervoso," Ann. Univ. di Med., April to June 1865, vol. 192, pp. 99-153.