The Penny Cyclopædia of The Society for the Diffusion of Useful Knowledge.
Fuego, Tierra Del - Haddingtonshire.
London: Charles Knight and Co., 22, Ludgate Street.
GALLS are the result of a morbid action excited in the leaf-buds of several species of the genus Quercus, or oak, occasioned by an insect, Cynips Quercus, depositing its ova, in the bud. Such buds, instead of elongating and becoming branches, undergo a peculiar transformation, and enlarge into a globular figure, so as to constitute a fit nidus for the future larva.
The galls of commerce are chiefly those which occur on the Quercus infectoria (011ivier). They vary in size, from that of a pea to that of a nutmeg: The surface has irregular elevations or lines, with the interspaces generally smooth. The colour is white or yellow in one variety; green, grey, or black in another. The white variety, which is the largest, often has a hole in the substance of the shell, by which the larva has escaped. This kind is the least powerful and least esteemed. The best galls come from Aleppo and Smyrna, but are often mixed with those from Syria and Cyprus. In 100 parts of Aleppo galls Sir H. Davy found gallic acid, 6.2; tannin, 26 ; gum and insoluble tannin, 2.4; lime and other salts, 2'4 ; woody fibre, 63. Braconnot also found ellagic acid. Galls are devoid of smell, but have a disagreeably bitter taste, with a powerfully astringent action. The whole of their soluble matter is yielded to forty times their weight of boiling water ; æther dissolves about half their weight, alcohol considerably more.
The infusion possesses all the valuable properties of the gall, as does an alcoholic tincture ; but decoction is an objectionable preparation. For internal use the infusion is preferable to the powder, which, like all substances containing much woody fibre, irritates the stomach. Galls may be employed in powder to form an ointment, which with opium and camphor is of great service in painful hæmorrhoids. As a tonic in intermittent fever, and as an astringent in hæmorrhagic or other discharges, galls are occasionally employed. But the most extensive use is made of them in the arts, and as a chemical test.