The presence of fatty oil in any considerable quantity is likewise made evident by the greasiness of the residue, when the balsam is deprived of its essential oil by prolonged boiling with water.
The admixture of some volatile oil with copaiba can mostly be detected by the odour, especially when the balsam is dropped on a piece of warmed metal. Spirit of wine may also be advantageously tried for the same purpose. It dissolves but very sparingly the volatile oil of copaiba: the resins of the latter are also not abundantly soluble in it. Hence, if shaken with the balsam, it would remove at once the larger portion of any essential oil that might have been added. For the recognition of Wood Oil if mixed with copaiba, [see page 233, note 1].
Substitutes—Under this head two drugs deserve mention, namely Gurjun Balsam or Wood Oil, described at [p. 88], and Oleo-resin of Hardwickia pinnata Roxb.—The tree, which is of a large size, belongs to the order Leguminosæ and is nearly related to Copaifera. According to Beddome,[897] it is very common in the dense moist forests of the South Travancore Ghats, and has also been found in South Canara. The natives extract the oleo-resin in exactly the same method as that followed by the aborigines of Brazil in the case of copaiba,—that is to say, they make a deep notch reaching to the heart of the trunk, from which after a time it flows out.
This oleo-resin, which has the smell and taste of copaiba, but a much darker colour, was first examined by one of us in 1865, having been sent from the India Museum as a sample of Wood Oil; it was subsequently forwarded to us in more ample quantity by Dr. Bidie of Madras. It is a thick, viscid fluid, which, owing to its intense tint, looks black when seen in bulk by reflected light; yet it is perfectly transparent. Viewed in a thin layer by transmitted light, it is light yellowish-green, in a thick layer vinous-red,—hence is dichromic. It is not fluorescent, nor is it gelatinized or rendered turbid by being heated to 130° C., thus differing from Wood Oil.[898] Broughton[899] obtained by prolonged distillation with water an essential oil to the extent of 25 per cent. from an old specimen, and of more than 40 per cent. from one recently collected. The oil was found to have the same composition as that of copaiba, to boil at 225° C., and to rotate the plane of polarization to the left. The resin[900] is probably of two kinds, of which one at least possesses acid properties. Broughton made many attempts, but without success, to obtain from the resin crystals of copaivic acid.
The balsam of Hardwickia has been used in India for gonorrhœa, and with as much success as copaiba.
GUMMI ACACIÆ.
Gummi Arabicum; Gum Arabic; F. Gomme Arabique; G. Arabisches Gummi, Acacien-Gummi, Kordofan-Gummi.
Botanical Origin—Among the plants abounding in mucilage, numerous Acaciæ of various countries are in the first line. The species particularly known for affording the largest quantities of the finest gum arabic is Acacia Senegal[901] Willdenow (syn. Mimosa Senegal L., A. Verek Guillemin et Perrottet), a small tree not higher than 20 feet, growing abundantly on sandy soils in Western Africa, chiefly north of the river Senegal, where it constitutes extensive forests. It is called by the negroes Verek. The same tree is likewise found in Southern Nubia, Kordofan, and in the region of the Atbara in Eastern Africa, where it is known as Hashab. It has a greyish bark, the inner layers of which are strongly fibrous, small yellowish flowers densely arranged in spikes 2 to 3 inches long, and exceeding the bipinnate leaves, and a broad legume 3 to 4 inches in length containing 5 to 6 seeds.
According to Schweinfurth,[902] it is this tree exclusively that yields the fine white gum of the countries bordering the Upper Nile, and especially of Kordofan. He states that only brownish or reddish sorts of gum are produced by the Talch, Talha or Kakul, Acacia stenocarpa Hochstetter, by the Ssoffar, A. fistula Schweinf. (A. Seyal Delile, var. Fistula), as well as by the Ssant or Sont, A. nilotica Desfont (A. arabica Willd.). These trees grow in north-eastern Africa; the last named is, moreover, widely distributed all over tropical Africa as far as Senegambia,[903] Mozambique and Natal, and also extends to Sindh, Gujarat[904] and Central India. We find even the first sort, “Karami,” of gum exported from the Somali coast,[905] to be inferior to good common Arabic gum. Hildebrandt (1875) mentions that gum is there largely collected from Acacia abyssinica Hochst. and A. glaucophylla Steudel.
History—The history of this drug carries us back to a remote antiquity. The Egyptian fleets brought gum from the gulf of Aden as early as the 17th century b.c. Thus in the treasury of king Rhampsinit (Ramses III.) at Medinet Abu, there are representations of gum-trees, together with heaps of gum. The symbol used to signify gum, is read Kami-en-punt. i.e. gum from the country of Punt. This, in all probability, includes both the Somali coast as well as that of the opposite parts of Arabia ([see article Olibanum, p. 136]). Thus, gum is of frequent occurrence in Egyptian inscriptions; sometimes mention is made of gum from Canaan. The word kami is the original of the Greek κόμμι, whence through the Latin our own word gum.[906]