Galls, Or Nntgalls, excrescences growing on a species of small oak, quercus infectoria, inhabiting Asia Minor and the middle latitude of Asia. They originate from the puncture of a fly, which deposits its egg in the young boughs, the egg and afterward the fly being enclosed in the centre of the gall. The galls collected before the egg is hatched are called blue, green, or black, and are the most valuable. The white galls, which are collected later, are injured by the insect. Galls reach the United States from Mediterranean ports and from Calcutta, They are nearly round, from the size of a pea to that of a very large cherry, with a surface usually studded with small tuberosities. The best are dark blue or green externally, lighter internally, hard and brittle, with a small cavity in the centre. Those of inferior quality are lighter in color, less hard, and contain a larger cavity communicating externally by a 2'ound hole through which the developed insect has escaped. Most if not all oaks contain a considerable amount of tannic acid, of that variety which precipitates the persalts of iron, blue-black. This acid seems to be concentrated in these pathological formations, constituting more than one half of their weight, and they are accordingly the source whence gallo- or querco-tannic acid is most conveniently obtained.
Galls have also been thought to contain smaller quantities of other allied acids, but it is probable that these are formed after the tannin and at its expense. All the soluble matter of galls is taken up by 40 times their weight of boiling water. Alcohol dissolves seven parts in ten, ether five. Galls are powerfully astringent, and may be used in medicine in the form of tincture or ointment, or in substance. For internal use, tannic or gallic acid is generally considered more convenient. The incompatibles of galls are very numerous, since the tannates of nearly all metallic oxides, alkalies, alkaline earths, and alkaloids are only slightly soluble in water. Nutgall ointment may be applied with advantage to haemorrhoids, but should not be used when the latter are inflamed. The dry substance is sometimes sprinkled over the surface of indolent ulcers or sores, to induce a healthy action in them.
Galls on the Quercus infectoria.