Gummi), is a concrete vegetable juice, of no particular smell or taste, becoming viscous and tenacious when moistened with water; totally dissolving in water into a liquid, more or less glutinous in proportion to the quantity of the gum; not dissolving in vinous spirits or in oils; burning in the fire to a black coal, without melting or catching flame; suffering no dissipation in the heat of boiling water.
The true gums are gum arabic, gum tragacanth, gum senega, the gum of cherry and plum trees, and such like. All else have more or less of resin in them.
Gum Arabic is the produce of a species of Mimosa; which tree.
The medical character of gum arabic is its glutinous quality, in consequence of which it serves to incrassate and obtund thin acid humours, so proves useful in tickling coughs, alvine fluxes, hoarsenesses, in fluxes of the belly with gripes, and where the mucus is abraded from the bowels or from the urethra. In a dysuria the true gum arabic is more cooling than the other simple gums, so should be preferred.
One ounce of gum arabic renders a pint of water considerably glutinous; four ounces gives it a thick syrupy con- consistence; but for mucilage, one part gum to two parts water is required; and for some purposes an equal proportion will be necessary.
In Dr Percival's Essays we have the following curious account, by Mr Henry, of the faculty which this gum hath of dissolving and keeping suspended in water not only resinous but also other substances, which should seem not likely to be at all affected by it.
"One scruple of balsam of tolu, rubbed with half an ounce of distilled rain-water, added gradually to it for 15 minutes, formed a mixture, which on standing about a minute subsided, but re-united by shaking: being set by a few days, the balsam became a concrete mass, not again miscible by shaking up the bottle. The same quantity required more trituration to mix it with common pump-water. One scruple of the same, rubbed with 15 grains of gum arabic, was nearly as long in perfectly uniting with half an ounce of distilled water as that without the gum. This was perhaps owing to the latter piece being more resinous; however, though on long standing there was a small sediment, it immediately reunited a week after by agitation. Fifteen grains of balsam capivi united very smoothly with half an ounce of distilled water, by the medium of three grains of gum arabic. Five grains of the gum were not so effectual with pump-water. Balsam Peru ten drops, with gum arabic three grains, distilled water half an ounce, formed a neat white emulsion, but with common water a very unequal mixture. Gum myrrh (powdered that there might be no difference in the several quantities used), half a scruple, dissolved readily with gum arabic three grains, in both kinds of water, and even mixed with them by longer trituration without any medium, but more easily with distilled than common spring water. Olibanum, maftich, gum guaiacum, and galbanum, may likewise be mixed with water by rubbing, without any gum arabic or egg. The spring-water made use of in these experiments was very aluminous.
"In the making of all the saline preparations, when any considerable quantities of water are used, distilled or pure rain or river water is greatly to be preferred; for the calcareous, aluminous, and selenetical matter, which so much abounds in most spring water, will render any salt dissolved in it very impure.
"The solution of crude mercury with mucilage of gum arabic being so easily accomplished, and it being very disagreeable to many patients, and to some almost impossible, to swallow pills, boluses, or electuaries, I was induced to try whether calomel, cinnabar, and the other heavy and metallic bodies commonly administered only under these forms, might not by the same means be rendered miscible with water, so as to be given more agreeably in a liquid form. I accordingly rubbed ten grains of cinnabar of antimony and a scruple of gum arabic, with a sufficient quantity of distilled water to form a mucilage, and added a drachm of simple syrup and three drachms more of water. This makes an agreeable little draught; and having stood about half an hour without depositing any sediment, I added three drachms more of water to it; and notwithstanding the mucilage was rendered so much more dilute, very little of the cinnabar subsided even after it had stood some days.
"Steel simply prepared, and prepared tin, were both No 145.
"Gum arabic was mixed with water by their own weight of gum arabic, and remained suspended, except a very small portion of each, which was not reduced to a sufficiently fine powder.
"Five grains of calomel were mixed with two drachms of distilled water and half a drachm of simple syrup by means of five grains of gum arabic, which kept it sufficiently suspended: a double quantity of the gum preserved the mixture uniform still longer. In this form it will be much more easily given to children than in syrups, conserves, &c. as a great part of it is generally waited, in forcing those vitid vehicles into them; and it may be joined with scammony and other resinous purgatives by the same method, and of these perhaps the gum arabic would be the best corrector.
"Gum arabic likewise greatly abates the disagreeable taste of the corrosive sublimate, mixed with water instead of brandy; and (from the few trials I have made) sits easier on the stomach, and will not be so apt to betray the patient by the smell of the brandy.
"Mr Plenck, who first instructed us in the method of mixing quicksilver with mucilage, observes (and experience confirms the truth of it), that this preparation is not so apt to bring on a spitting as the argent. nit. mixed by any other medium, or as the saline and other mercurial preparations.—How far the theory by which he accounts for it may be just is not of much importance; but it may perhaps be worth while to inquire, whether it would not be equally effectual in preventing calomel, and the other preparations of mercury, from affecting the mouth.—If so, is it not improper, where a salivation is intended, to give emulsions with gum arabic and other mucilaginous liquors for the patient's common drink, as by that means the spitting may be retarded? And, on the contrary, may it not be a useful medicine to diminish the discharge when too copious?
"The following case may in some measure serve to confirm the above observation.—A gentleman, always easily affected by mercurials, having taken about 26 grains of calomel in doses from one to three grains, notwithstanding he was purged every third day, was suddenly seized with a salivation. He spat plentifully, his breath was very fetid, teeth loose, and his gums, fauces, and the margin of his tongue, greatly ulcerated and inflamed. He was directed to use the following gargle. R. Gum. arab. seminunc. solv. in aqua font. bullient. feliq. & adde mel. refac. unc. unam. M. ft. gargar. And to drink freely of a ptifan prepared with ag. bord. lib. ij. gum. arabic. unc. ij. nitr. pur. drachm. ij. sacchar. alb. unc. j. His purgative was repeated the succeeding morning. The next day his gums were less inflamed, but the sores on his tongue, &c. were still as foul: his spitting was much the same: he had drank about a pint of the ptifan. Some fpt. vitrioli was added to the gargle. From this day to the fourth he was purged every day without effect, his salivation still continued, his mouth was no better, he had neglected the mucilaginous drink. This evening he was persuaded to drink about a pint of it which remained, and he had it repeated, and drank very freely of it that night. On the fifth morning the purgative was again repeated. Though it operated very little, yet the change was very surprising: his mouth was nearly well, and his ptyalism greatly decreased. The ptifan was repeated; and on the fifth day, being quite well, he was permitted to go abroad."
In Mr Haffelquist's Travels we have an instance of the extraordinary nutritive virtues of this gum. "The Abyssinians (says he) make a journey every year to Cairo, to sell the products of their country. They must travel over terrible deserts, and their journey depends as much on the weather as a voyage at sea; consequently they know as little as a seaman how long they must be on their journey; and the necessities of life may chance to fail them when the journey lasts too long. This happened to the Abyssinian caravan in the year 1740, their provisions being consumed when they had still two months to travel. They were then obliged to search for something among their merchandise wherewith they might support nature; and found nothing more proper than gum arabic, of which they had carried a considerable quantity along with them. This served to support above 1000 persons for two months; and the caravan at last arrived at Cairo without any great loss of people either by hunger or disease."
Gum Seneca, is a gum extremely resembling gum arabic. It is brought to us from the country through which the river Senega runs, in loose or single drops; but these are much larger than those of the gum arabic usually are; sometimes it is of the bigness of an egg, and sometimes much larger; the surface is very rough or wrinkled, and appears much less bright than the inner substance where the masses are broken. It has no smell, and scarce any taste. It is probably produced from a tree of the same kind with the former. The virtues of it are the same with the gum arabic; but it is rarely used in medicine, unless as mixed with the gum arabic; the dyers and other artificers consume the great quantities of it that are annually imported hither. The negroes dissolve it in milk, and in that state make it a principal ingredient in many of their dishes, and often feed on it thus alone.
Gum Tragacanth, the gum of the tragacanth, a thorny bush growing in Crete, Asia, and Greece. See Astragalus.
Other substances known by the name of gums are as follow:
- Gum Ammoniac. See Ammoniac. - Gum Elemi. See Amyris. - Gum Keno. See Keno. - Gum Guaiacum. See Guaiacum. - Gum Laccas. See Coccus and Lacca.
Gum, among gardeners, a kind of gangrene incident to fruit trees of the stone kind, arising from a corruption of the sap, which, by its viscidity, not being able to make its way through the fibres of the tree, is, by the protrusion of ether juice, made to extravasate and ooze out upon the bark.
When the distemper surrounds the branch, it admits of no remedy; but when only on one part of a bough, it should be taken off to the quick, and some cow-dung clapped on the wound, covered over with a linen cloth, and tied down. M. Quinunie directs to cut off the morbid branch two or three inches below the part affected.