GUM

n. Gusm. Gr., <W' (1st def.), ofaov (3d def.). Lat., gummi (1st def.). gingiva (3d def.). Fr., gomme (1st def.), gencive '(3d def.). Ger., Gummi (1st def.), Zahnfleisch (3d def.). It., gomma (1st def.), gengiva (3d def.). Sp., goma (1st def.), encia (3d def.). 1. A thick, viscid, tenacious exudation from the stems, branches, or fruits of plants, which hardens on exposure to the air into a transparent, amorphous, vitreous ma , is converted into glucose by dilute sulphuric acid, is insoluble in alcohol, and is distinguished from a resin by being soluble in water, forming with it a mucilage, or at least being softened by it (cf. G.-resin). It is produced from vegetable cells by the solution and rupture of the cell-wall, and the discharge, coalescence, and subsequent hardening of the cell-contents. This initiatory rupture is probably secondary to a degeneration in the cellulose of which the cell-wall is composed (g.-discase of plants), and has been thought due to the presence of a bacterium. Chemically, the g's are complex compounds of various metallic elements with one or more proximate principles (often improperly termed g's) analogous in structure to the carbohydrates, being probably diglucosic alcohols (arabin. ba or in, and cerasin). G; is used in medicine, chiefly as a demulcent, an excipient, or as a menstruum in which to suspend insoluble drugs. In the arts it is employed as an adhesive paste (see PASTA gummosa) and to stiffen and give lustre to fabrics. For the individual g's not here mentioned, see the major list. 2. Caoutchouc; used in this sense especially in composition. [B, 4, 5; B, 77 (o. 24).] 3. The ti ue overlying the alveolar proce es of the maxillary bones (to the periosteum of which it is closely adherent) and surrounding the bases of the teeth. It consists of dense fibrous ti ue covered by a vascular but almost insensitive mucous membrane, presenting around the necks of the teeth numerous fine papilla?. [A, 478 (a, 17).] Acaroid g. See U, blue; U3, lull; U4, full; U8, urn; U6, like ii (German). [s. 251]