(Tsama/i, pronounced ghamah; Hebrew,) gum, gisisim, is a concrete vegetable juice, of no particular smell or taste, viscous and tenacious when moistened with, and wholly soluble in, water; insoluble in alcohol or in oils; burning in the fire to a black coal, without melting or inflaming, and not volatile in the heat of boiling water.
The true gums are gum arabic, tragacanth, and senega: the gum of cherry and plum trees: the others contain a proportion of resin.
The virtues of gums are those of mucilages in general, which are only gums with a proportion of water. When the ancients used the word gummi, or commi. without any epithet, they meant gum arabic. The (Hippocrates De Morbis Mulierum,) is the same.
Gummi Arabicum, called also acanthinum; gum lamac; gum Thebaicum and Serapionis, gum Arabic, and the true gum acacia. It exudes from the Egyptian acacia, or thorn tree, whose fruit affords the inspissated juice of that name. Mimosa nilotica Lin. Sp. Pi. 1506. (See Acacia.) It is brought from Turkey in small irregular masses, of a clear whitish or very pale yellow colour.
Though insoluble in spirit, and in oil, yet, when formed into a mucilage, it is miscible with both, and with resins rendering them miscible with water. Dr. Grew first taught us to mix essential oil with water by means of gum; and in the London Medical Observations and Inquiries, vol. i. we find that oils, both expressed and distilled, resins, and balsams, may, by the same means, be mixed uniformly with water or with spirit. Alkaline salts, both fixed and volatile, though they render pure oil miscible with water, prevent the mixture of gum with oil. Acids do not in the least prevent the effect of gum in combining oils with water.
Animal glues very unlike vegetable gums are more nutritious, and apt to become putrid; and they will not combine oil with water. In a chemical view their difference is very great; those of the animal kind are changed by fire into a volatile alkaline salt, and a fetid oil; the vegetable into an acid liquor, and a very minute portion of oily matter, considerably less fetid than the former.
Gum arabic is glutinous and demulcent; consequently useful in tickling coughs, diarrhoeas, hoarseness, in cardialgia, when from any oily aliment, and in almost every disease of the urinary organs. In dysuria the true gum arable is preferable to the other simple gums. Though its action has been supposed not to extend beyond the glottis and the alimentary canal, it is certainly conveyed with little change to the kidneys; and, when used in moderate quantities, even checks the urinary discharge. To be effectual as an internal demulcent, two ounces a day should be, at least, taken. Dr. Has-selquist informs us, that a caravan, whose provisions were exhausted, found it very nutritive.
One ounce of gum arabic renders a pint of water considerably glutinous; but for mucilage, one part of gum to two parts water is required, and for some purposes an equal proportion will be necessary. See Lewis's Materia Medica; Neumann's Chemical Works.
Gummi funerum. See Bitumen.
Gummi resina lutea. New Holland has furnished two new medicines; the red and the yellow gum. The first is astringent, and not unlike the kino described in the following article. The yellow is not very dissimilar; but the plant from which each is procured has not been reduced to its place in botanical systems.
Gummi rubrum astringens Gambiense. The Red Astringent Gum From Gambia; Kino; Sanguis draconia officinalis, or the finest and true dragon's blood. Dr. Oldfield calls it true gum Senegal. In the inland parts of Africa it is called pau de sangue: pau is said to be a corruption of palo, wood; and, with the addition of sangue, to be the name of a tree in the inland parts of Africa which produces it.
Gum kino is very friable, easily breaking between the fingers; without smell, of an opake, dark, reddish colour, appearing almost black in the mass, and, when powdered, of a deep lateritious red. In chewing, it first crumbles, then coheres slightly, and seems soon to dissolve, with a very astringent slightly sweet taste.
It differs from the red lumps of the common gum Senegal in being much more brittle; and from the dragon's blood in its affinity to water; and from both in its stypticity when tasted. It dissolves both in spirit and in water; each taking up about two thirds of the whole.
This gum seems useful in many disorders from laxity, as in chronic diarrhoea, leucorrhoea, and maenorrhagia. It contains a larger proportion of gum than any other astringent drug, and, joined with alum, in the proportion of one part to three, (as in the pulvis stypticus, Ph. Edin.) is considered to be one of the most powerful astringents which has been employed. In a liquid form, however, the kino is said by Tromsdorff to decompose the alum; but this effect appears to depend on some accident, as the experiment does not always succeed. Cullen's Materia Medica; London Medical Observations and Inquiries, vol. i. p. 358, etc.
Gummi Senegalense, gum Senega, and gum Orientate, is brought from the island Senegal, on the coast of Africa, and is said to be the production of the tree which affords the gum arabic.
This gum is generally in larger and darker pieces than the gum arabic, and rough on the outside: the gum arabic also is dry and brittle, but the Senega clammy and tenacious. The clearest pieces are sold for gum arabic, and their qualities are nearly similar; but the gum Senega is certainly more adhesive.
Gummi tragacantha, (from a goat, and a thorn, because its pods resemble a goat's beard,) adraganth, and dragantum; gum dragant, or tragacanth. This gum exudes from a prickly bush, which grows in Crete, Greece, and Asia. Astragalus tragacantha Lin. Sp. Pl. 1073. Goat's thorn, or milk vetch. It is chiefly brought to us from Turkey in irregular lumps, or in long vermicular pieces. In Candy it begins to exude about June, and is more or less pure and white, according to its accidental mixture with dust. That which is white, light, smooth, and transparent, in vermicular striae, of a sweetish taste, and without smell, is preferred. A yellowish or brownish colour is no mark of imperfection or impurity.
It differs from all other gums in giving a thick consistence to a larger quantity of water, probably from being insoluble in this fluid, which it slowly imbibes in a large proportion, swells into a considerable bulk, and forms a soft, but not liquid mucilage. On the further addition of water a fluid solution may be obtained by agitation, but the liquor is turbid; and, on standing, the mucilage subsides, the limpid water on the surface retaining little of the gum. It is more powerful as a mucilage than other gums but not as a demulcent, though it softens and thickens acrid humours.
The pulvis e tragacantha compositus of the London college is made in the following manner: Tragacan-thae in pulverem tritae, gum. arabici, amyli, singulorum i. ss. sacchari purificati iij. simul in pulverem tere. Ph. Lond. 1788.
It is mild, emollient, and useful in tickling coughs, and supposed to mix oils and resins more smoothly than the gum arabic. See Lewis's Materia Medica; Neumann's Chemical Works; Cullen's Materia Medica.