Gall, in natural history, signifies any protuberance, or tumor, produced by the punctures of insects on plants and trees of various kinds ; but especially the quereus, or oak ; cistus, or rock-rose ; gle-choma hederacea, or ground-ivy; salix, or willor; hieraceum, or hawkweed ; salvia, or clary ; ve-ronica, or speedwell, etc.
Insects deposit their eggs in the leaves or tender branches of plants, the juice of which exudes, and in a short time forms tumors around the punctures or holes. The external coat of this excrescence is dried by the air, and during the winter affords a secure shelter to the inclosed insect, while the soft inner pulp furnishes it with sustenance till the spring approaches, when the fly perforates the shell or rind, and departs.
The best of these galls are those found on oak-trees, and which are thence called oak-galls; they are deposited by the cynips quercus gemmae, or oak-bud cynips. - A small portion of galls infused in a weak solution of vitriol in water, imparts to it a purple or violet tint; which, after the whole of the colouring matter is extracted, becomes perfectly black. Considerable quantities of this drug are used in .Britain, for the making of ink, dyeing cloths of a black colour, and also for the dressing of leather. - The most esteemed galls are brought from Aleppo in Syria; and by the 8th Geo. I. c. 15, s. 10, are allowed to be imported duty-free, excepting the payment of 4s. 1 d. per cwt. for convoy-duty. . Galls have an austere styptic taste, without any smell: they are very powerful astringents, and have, therefore, often been employed in medicine. It is asserted that, by their internal use, in doses of half a dram or more of the powder, intermittent fevers have been cured, even after Peruvian bark had failed.
Although we have met with no remedy for the cure of this complaint, yet, for its prevention, the following useful fact deserves to be recorded. Mr. Ellman, of Shoreham, Sussex, has observed, that by giving his sheep some hay in mornings of hoar-frosts, it preserves them from the gall.