Quercus Infectoria. Dyer's oak, Nut-galls.
Description: With the same family and generic characteristics as quercus alba. This species is most abundant in Asia Minor, and extends to middle Asia. A small tree from four to six feet high, crooked and shrubby-looking, with smooth and bright-green leaves. Acorn long and narrow, cup short, scaly, and downy.
This tree is valued for excrescences which are formed upon the young branches, and which are known in market under the names of galls and nut-galls. They are the result of a puncture made in the bark by an insect (Diplolepis gallae tinctoriae, or Cynips quercufolii) for the purpose of depositing its egg. A small tumor soon follows the puncture, and forms a very dense mass about the egg. The egg hatches into the fly while in these tumors, eating its way by a small opening. The excrescences vary from the size of a large pea to that of a small hickory-nut, are nearly round, hard, and quite smooth with the exception of small tubercles scattered over the surface. Those in which the egg has not yet turned into larva are most compact and heavy, of a dark blue or bluish-green color externally, grayish-brown internally, and of an almost flinty fracture. When the larva has been developed, the external color lightens; and those of large size and grayish appearance are more or less fed upon internally by the grub, and depreciate in value.
Galls abound in tannin, containing more than sixty per cent. of this astringent substance; also a small percentage of gallic and some other acids. They are the chief source of commercial tannic acid; and by suitable manipulation are made to yield a large percentage of gallic acid, at the expense of their tannin. Forty times their own weight of boiling water are said to dissolve out all the soluble elements, but a larger quantity is needed to prevent a small yellowish precipitation on cooling. Alcohol and ether act on them freely. Their decoction or tincture forms bluish-black precipitates with salts of iron, and is a basis in all black writing inks. They also form insoluble precipitates with gelatin, cinchona, columbo, and other vegetables containing alkaloids.
Properties and Uses: Galls are purely and powerfully astringent, scarcely stimulant. Are rarely employed by the stomach, though sometimes prescribed (to no great advantage) in chronic diarrhea. They may be used as a wash and gargle in aphthous sores and putrid sore throat, and as an injection in bad leucorrhea; in which cases they arrest putrefactive tendencies, and may be combined with suitable stimulants. By coagulating the blood, they frequently will arrest hemorrhage from small vessels; and sometimes are used for bleeding piles, both as ointment and suppository, but are inadmissible when the tumors are sensitive. From five to fifteen grains have been used internally. A tincture is made by macerating four ounces of galls in diluted alcohol for two days, and then treating them by percolation (in a porcelain apparatus) till a quart has passed. It is rarely used. Age impairs its astringency. One ounce of powdered galls rubbed into seven ounces of lard, forms the usual ointment.
The Physiomedical Dispensatory, 1869, was written by William Cook, M.D.
It was scanned by Paul Bergner at http://medherb.com
