CHAP. 20. (11.)—NINE KINDS OF GUM. THE SARCOCOLLA.
It is universally agreed, that the best gum is that produced
from the Egyptian thorn;[1] it is of variegated appearance, of
azure colour, clean, free from all admixture of bark, and
adheres to the teeth; the price at which it sells is three
denarii per pound. That produced from the bitter almond-
tree and the cherry[2] is of an inferior kind, and that which is
gathered from the plum-tree is the worst of all. The vine,
too, produces a gum,[3] which is of the greatest utility in healing
the sores of children; while that which is sometimes found on
the olive-tree[4] is used for the tooth-ache. Gum is also found
on the elm[5] upon Mount Corycus in Cilicia, and upon the
juniper,[6] but it is good for nothing; indeed, the gum of the
elm found there is apt to breed gnats. From the sarcocolla[7]
also—such is the name of a certain tree—a gum exudes that is
remarkably useful to painters[8] and medical men; it is similar
to incense dust in appearance, and for those purposes the white
kind is preferable to the red. The price of it is the same as
that mentioned above.[9]
1. The Acacia Nilotica of Linnæus, from which we derive the gum
Arabic of commerce; and of which a considerable portion is still derived
from Egypt.
2. These gums are chemically different from gum Arabic, and they are
used for different purposes in the arts.
3. The vine does not produce a gum; but when the sap ascends, a juice
is secreted, which sometimes becomes solid on the evaporation of the
aqueous particles. This substance contains acetate of potassa, which, by
the decomposition of that salt, becomes a carbonate of the same base.
4. This is not a gum, but a resinous product of a peculiar nature. It is
known to the moderns by the name of "olivine."
5. The sap of the eim leaves a saline deposit on the bark, principally
formed of carbonate of potassa. Fée is at a loss to know whether Pliny
here alludes to this or to the manna which is incidentally formed by certain
insects on some trees and reeds. But, as he justly says, would Pliny say
of the latter that it is "ad nihil utile"—"good for nothing"?
6. A resinous product, no doubt. The frankincense of Africa has been
attributed by some to the Juniperus Lycia and Phoenicia.
7. The Penæa Sarcocolla of Linnæus. The gum resin of this tree is
still brought from Abyssinia, but it is not used in medicine. This account
is from is Dioscorides, B. iii. c. 99. The name is from the Greek sarc,
"flesh," and ko/lla, "glue."
8. See B. xxiv. c. 7.
9. Three denarii per pound.