The Egyptians used gum largely in painting; an inscription exists which states that in one particular instance a solution of Kami (gum) was used to render adherent the mineral pigment called chesteb,[907] the name applied to lapis lazuli or to a glass coloured blue by cobalt.
Turning to the Greeks, we find that Theophrastus in the 3rd and 4th century b.c. mentioned Κόμμι as a product of the Egyptian Ἂκανθα, of which tree there was a forest in the Thebaïs of Upper Egypt. Strabo also, in describing the district of Arsinöe, the modern Fayûm, says that gum is got from the forest of the Thebaïc Akanthe.
Celsus in the 1st century mentions Gummi acanthinum; Dioscorides and Pliny also describe Egyptian gum, which the latter values at 3 denarii [2s.] per lb.
In those times gum no doubt used to be shipped from north-eastern Africa to Arabia; there is no evidence showing that Arabia itself had ever furnished the chief bulk of the drug. The designation gum arabic occurs in Diodorus Siculus (2, 49) in the first century of our era, also in the list of goods of Alexandria mentioned in our article on Galbanum.
Gum was employed by the Arabian physicians and by those of the school of Salerno, yet its utility in medicine and the arts was but little appreciated in Europe until a much later period. For the latter purpose at least the gummy exudations of indigenous trees were occasionally resorted to, as distinctly pointed out about the beginning of the 12th century, by Theophilus or Rogker:[908] “gummi quot exit de arbore ceraso vel pruno.“
During the middle ages, the small supplies that reached Europe were procured through the Italian traders from Egypt and Turkey. Thus Pegolotti,[909] who wrote a work on commerce about a.d. 1340, speaks of gum arabic as one of the drugs sold at Constantinople by the pound not by the quintal. Again, in a list of drugs liable to duty at Pisa in 1305,[910] and in a similar list relating to Paris in 1349,[911] we find mention of gum arabic. It is likewise named by Pasi,[912] in 1521, as an export from Venice to London.
Gum also reached Europe from Western Africa, with which region the Portuguese had a direct trade as early as 1449.
Production—Respecting the origin of gum in the tribe Acaciæ, no observations have been made similar to those of H. von Mohl on tragacanth.[913]
It appears that gum generally exudes from the trees spontaneously, in sufficient abundance to render wounding the bark superfluous. The Somali tribes of East Africa, however, are in the habit of promoting the outflow by making long incisions in the stem and branches of the tree.[914] In Kordofan the lumps of gum are broken off with an axe, and collected in baskets.
The most valued product, called Hashabi gum, from the province of Dejara in Kordofan, is sent northward from Bara and El Obeid to Dabbeh on the Nile, and thence down the river to Egypt; or it reaches the White Nile at Mandjara.