FABACE^E. 271 



stated by Forskal to afford a gum, which is gathered by the Arabs. Dr. 

 Pereira thinks that what is called Barbary gum is in part at least, the product 

 of this tree, and Dr. Lindley says that it is by no means certain that Gum 

 Sassa is not produced by it. 



Besides these, it is stated on good authority, that several other species not 

 only secrete an analogous juice, but that a large portion of the gum of com- 

 merce is derived from them : these are — 



4. A. seyal, Delille. — A native of Egypt and Senegambia. This yields part of the 

 gum Senegal. This gum occurs in white, hard, vitreous, reniform pieces. 



5. A. Senegal, Willdenow. — Is found in Arabia and in Africa, from Senegal to the 

 Cape of Good Hope. It produces gum Senegal. It is A. verek. Adanson. 



6. A. tortilis, Forskal. — A native of Arabia ; the gum is collected by the Arabs, and 

 is said to be of very fine quality. 



7. A. ehrenbergii, Hayne. — Also a native of Arabia, and affords a product like the 

 last. 



All these species, and probably many others, are exceedingly similar in 

 their appearance and habits, and the gum from them is almost identical, vary- 

 ing more in appearance and purity, than in composition and uses. The 

 Acacia and its product has been known from the earliest antiquity. The 

 Shittim tree, mentioned in several places in the Old Testament, is- generally 

 supposed to have been an Acacia. The author of the notes to the Pictorial 

 Bible (i. 202) is of opinion that it was A. horrida, and Dr. Carpenter to be 

 A. vera. Hippocrates also speaks of the Acacia under the names of Egyptian 

 thorn and white thorn, and likewise mentions the gum as useful in medicine. 

 Pliny alludes to a tree under the name of Spina sitiens, which there is reason 

 to believe was a species of this genus. It was of course well known to the 

 Arabian physicians. 



There are numerous varieties of gum found in commerce, known under 

 the names of Gum Arabic, Gum Senegal, Barbary Gum, East India Gum, 

 Cape Gum, &c, all possessing the same characteristics, the finer portions of 

 them being sold as Gum Arabic, a full account of which will be found in 

 Guibourt, Histoire des Drogues, and a good synopsis of their peculiarities in 

 Pereira, Elements Mat. Med. ii. 579, &c. 



Gum flows naturally from the gum-bearing Acacias at certain seasons of 

 the year, principally during the hot months ; but to increase the discharge, 

 incisions are also made. Jackson [Morocco, 137) says, " that the more sickly 

 the trees appear, the more gum they yield, and the hotter the weather, the more 

 prolific it is." In Senegal, Adanson, however, says that the greatest flow is 

 during the rainy season. 



As found in the market, Gum Acacia is in tears or fragments of different 

 sizes, wholly inodorous, but with a slightly sweetish, mucilaginous taste. 

 These may be transparent and colourless, or opaque and dark-coloured, or 

 with any of the intermediate characters. Gum dissolves both in hot and cold 

 water, forming a mucilage. It is insoluble in alcohol, which precipitates it 

 from its watery solution. According to the analysis of Guerin and others, 

 Gum Acacia is composed of about three-fourths of soluble gum or Arabine, 

 the rest being water, &c. When pure, it contains no Bassorine, so large a 

 constituent of Gum Bassora, the product of an unknown plant. 



Medical Uses, Src — Gum is employed as a demulcent, and as an article 

 of diet in cases of irritation of the alimentary canal. Although from its mild- 

 ness, it causes no uneasiness to the digestive organs, it is very nutritious, and 

 in fact it forms a very large constituent of many kinds of vegetable food. But 



