067. Mimosa nilotica. Egyptian mimosa, Acacia, Egyptian thorn.
Also see 066. Mimosa catechu. Catechu mimosa.
Gummi Arabicum, Pharm. Lond. & Edinb. Sponte ex hac planta fluit.
Synonyma. Acacia vera. J. Bauh. Hist. vol. i. p. 429.
Acacia foliis scorpioides leguminosae. Bauh. Pin. 392.
Acanthus Theophrasti. Raii. Hist. p. 976.
Acacia vera sive spina Aegyptiaca. Park. Theat. p. 1547.
Acacia vera s. Spina Aegyptiaca, subrotundis foliis flore luteo; siliqua paucioribus isthmis glabris nigricantibus. Pluk. Alm. 3. t. 123. f. 1.
Acacia Aegyptiaca siliquis Lupini, floribus luteis. Herm. Parad. Bat. Prod. 303. Conf. Hasselq. it. p. 475.
(greek) Dioscorid. L. 1. cap. 133.
Class Class Polygamia. Ord. Monoecia. Lin. Gen. Plant. 1158.
Ess. Gen. Ch. Hermaph. Cal. 5-dentatus. Cor 5-fida. Stam. 5. s. plura. Pist. 1. Legumen. Masc. Cal. 5-dentatus. Cor. 5-fida. Cor. 5-fida. Stam. 5, 10, plura.
Spec. Char. M. spinis stipularibus patentibus, foliis bipinnatis: partialibus extimis glandula interstinctis, spicis globolis pedunculatis.
This, like the preceding species of Mimosa, rises several feet in height: it is covered with smooth bark of a grey colour, and that of the branches has commonly a purplish tinge: the leaves are bipinnated, and placed alternately: the partial pinnae are opposite, furnished with a small gland between the outermost pair, and beset with numerous pairs of narrow elliptical pinnulae, or leafits: the spines are long, white, spreading, and proceed from each side of the base of the leaves: the flowers are hermaphrodite and male, they assume a globular shape, and stand four or five together upon slender peduncles, which arise from the axillae of the leaves: the calyx is small, bellshaped, and divided at the mouth into five minute teeth: the corolla consists of five narrow yellowish segments: the filaments are numerous, capillary, and furnished with roundish yellow antherae: the germen is conical, and supports a slender style, crowned with a simple stigma: the fruit is a long pod, resembling that of the Lupin, and contains many flattish brown seeds. It is a native of Arabia and Egypt, and flowers in July. [The M. nilotica was cultivated in England by Evelyn in 1664. Kalend. h. p. 75. A plant of this species is now in the Royal Garden at Kew, about four feet in height: and in Dr. Lettsom's garden at Grove Hill, where it flowers annually.]
Dioscorides was certainly well acquainted with this tree, as he not only mentions the gum which it produces, but also the renowned Acacia verae succus [The pod, and manner of preparing the juice, are thus mentioned by Murray: "Ex fructu elicitur, qui ipse legumen est complanatum viridi brunum, quatuor vel quinque pollices longum et octies vel decies angustius, compositum ex sex vel decem partibus vel articulis discoideis et intra utramque cuticulam parenchyma gummosum rubicundum continens. In quovis articulo latet semen ellipticum sulco utrinque pariter elliptico notatum. Succus exprimitur ex fructu immaturo in mortario contuso, et calore in spissitudinem extracti densatur," &c. Vide App. Med. vol. ii. p. 412.] obtained from its pods; since his time, however, it has been thought that gum arabic is not the production of the Acacia or Mimosa, as it is now called; but the accounts given by Alpinus, and those of subsequent naturalists, leave no doubt upon this subject. [Hasselquist. Adanson, Sparrman, and others.]
Although the Mimosa nilotica grows in great abundance over the vast extent of Africa, yet gum arabic is produced chiefly by those trees, which are situated near the equatorial regions; and we are told that in Lower Egypt the solar heat is never sufficiently intense for this purpose. [Niebuhr Reisebesch. Arab. 1. B. p. 143.] The gum exudes in a liquid state from the bark of the trunk and branches of the tree, in a similar manner to the gum which is often produced upon the cherry trees, &c. in this country; and by exposure to the air it soon acquires solidity and hardness. In Senegal the gum begins to flow when the tree first opens its flowers, [Adanson Mem. de l'Ac. d Sc. d. Paris, 1773. p. 8.] and continues during the rainy season till the month of December, when it is collected for the first time. Another collection of the gum is made in the month of March, from incisions in the bark, which the extreme dryness of the air at that time is said to render necessary. [Demanet Nouvelle Hist. de l'Afrique Françoise, t. 1. p. 56.]
Gum arabic is now usually imported into England from Barbary, not packed up in skins, which was the practice in Egypt and Arabia, but in large casks or hogsheads. The common appearance of this gum is so well known as not to require any description of it here; and the various figures which it assumes seem to depend upon a variety of accidental circumstances attending its transudation and concretion.
Gum Arabic of a pale yellowish colour is most esteemed; on the contrary, those pieces which are large, rough, of a roundish figure, and of a brownish or reddish hue, are found to be less pure, and are said to be produced from a different species of Mimosa: (M. Senegal) but the Arabian and Egyptian gum is commonly intermixed with pieces of this kind, similar to that which comes from the coast of Africa, near the river Senegal. Gum Arabic does not admit of solution by spirit or oil, but in twice its quantity of water it dissolves into a mucilaginous fluid, of the consistence of a thick syrup, and in this state answers many useful pharmaceutical purposes, by rendering oily, resinous, and pinguious substances, miscible with water. [See Mr. French's Experiments in Lond. Med. Observ. vol. i. p. 413, &c.]
The glutinous quality of gum arabic is preferred to most other gums and mucilaginous substances as a demulcent, in coughs, hoarsenesses, and other catarrhal affections, in order to obtund irritating acrimonious humours, and to supply the loss of abraded mucus. It has been very generally employed in cases of ardor urinae, and stranguary: but it is the opinion of Dr. Cullen, "that even this mucilage, as an internal demulcent, can be of no service beyond the alimentary canal. In common practice hardly more than a few ounces are given in one day; and what that can give of a mucilaginous quality to many pounds of serosity, I leave my intelligent reader to judge. Still, however, it may not be thought enough to reason a priori, and I should say, what experience has actually taught. What others may have observed, I cannot determine; but, for myself I can assert, that, in innumerable trials, I have never observed the effects of gum arabic in the mass of blood, or in the excretions derived from it. The most frequent occasion for its use is in the ardor urinae; and in that I have been often disappointed, and have often found that two pounds of water or watery liquors added to the drink, would be of more service than four ounces of gum arabic taken in without such addition." [Mat. Med. p. 415. vol. 2.] This gum is an ingredient in the Hartshorn decoction, the chalk Julep, the common emulsion, and some of the troches as directed in our Pharmacopoeias.
Gum arabic has been found a good substitute for food; and Dr. Sparrman tells us, that he pointed out this gum to the Hottentots, "which they might gather in many spots thereabouts from the Mimosa nilotica; but this was a species of food very well known to them, and which they had often tried.—When in want of other provisions, the Boshies-men are said to live upon this for many days together."——Voyage to the Cape, vol. ii. p. 23.