1930 ARliOUETUM AND FRUTICETUM. PART 111. 



being slightly exposed. After impregnation, the eggs are deposited by means 

 of this boring instrument, which is exsertile, within the leaves or twigs of 

 various plants ; shortly after which the galls are formed on the outside of the 

 attackcti part, the eggs being forced from the place where they were originally 

 deposited, and occupying the centre of the newly formed gall, which is gene- 

 rally of a fleshy nature, and serves as food to the young grub {fg. 1822. b), 

 when hatched; the pupa state (fig. 1822. c) succeeds, and is passed cither 

 within the gall, as in the insect now under consideration, or in the earth ; 

 the larva having previously to its change eaten its way out ; soon after which, 

 the insect assumes its imago state. Hence, it will be at once obvious, that a 

 gall, from which the insect has escaped, must necessarily contain less astringent 

 principle than one which has its interior less consumed by the insect, which 

 still remains enclosed therein; and hence it is that there are two kinds of gall 

 nuts known in commerce : those which still contain the insect, and which are 

 known in the trade under the names of black or blue galls and green galls, and 

 termed ycrli by the natives of the countries where they are collected ; and 

 those from which the insect has escaped, and which are called white galls. 

 The latter contain not more than two thirds of the astringent cjualities of the 

 former, and are of a pale brown or whitish colour, less compact, and not so 

 heavy. (Oliv. Voy. dans I'Emph-c Oltonian ; and Travels in Egy2>t, vol. ii. p. 6 1 .) 

 Mr. M'CuUoch states that these galls "are principally exported from Aleppo, 

 Tripoli, Smyrna, and Said : those brought from the first come chiefly from 

 Mosul, on the western bank of the Tigris, about 10 days' journey from Aleppo, 

 The real Mosul galls are unquestionably the best of any : but all that are 

 gathered in the surrounding country are sold under this name. Those from 

 Caramania are of very inferior quality. The gall nuts met with in India are 

 carried thither from Persia by Arabian merchants." (Com. Diet., p. 593.) 

 General Hardwicke, however, states that he discovered the tree upon which 

 they are found in the neighbourhood of Adwuanie. (Asiat. Rep., vol. vi. 

 p. 376.) " The price of galls, in the London markets, varies from 65*. to 

 85*. per cwt. The duty is 5*. per cwt." (M'Ciill. Com, Diet., art. Gall.) The 

 white and blue galls are generally sold mixed together in about equal propor- 

 tions, and are then called galls in sorts ; and occasionally fraud is attempted 

 by dyeing the white galls with a blue dye, but their lighter weight will render 

 it easy to detect them at once. 



The chief use made of these galls is in the manufacture of common writing 

 ink, which is made by adding an infusion of the gall nut to sulphate of iron dis- 

 solved in water. A very^ne precipitate is thrown down, the speedy subsidence 

 of which is prevented by the addition of a proper quantity of gum arable. This 

 is usually accounted for by the superior affinity of the gallic acid ; which, com- 

 bining with the iron, takes it from the sulphuric acid, and occasions it to fall 

 down. Logwood is also a usefid ingredient in ink, its colouring matter uniting 

 with the oxide of iron, and rendering it not only of a very dark colour, but less 

 liable to change from the action of acids, or the external air. The application 

 of heat is also necessary; because by its action the galls are almost entirely 

 soluble in water, which is not the case when they are simply macerated. 

 Gallic acid may be obtained from the infusion, merely by sublimation. The 

 solution also contains a large quantity of tannin, as it gives a very copious 

 precipitate with solution of gelatine. The proportion of these ingredients in 

 815 grains of solid matter are, according to Sir Humphry Davy, as follows : — 

 130 of tannin, 31 gallic acid, 12 saline and earthy matter, and 12 supposed to 

 be mucilage and extractive matter. (Tall nuts are also very extensively used 

 in dyeing; and, being the most powerful of vegetable astringents, " they are fre- 

 quently used with great effect in medicine, both externally and internally, in 

 the form of powders, infusions, tinctures, or ointments; as in long protracted 

 and obstinate diarrhoeas, intestinal haemorrhages, and intcrmittents; and, 

 when judiciously combined with tonics and aromatics, have been found useful. 

 Much caution is, however, re(|uired in adn)inistering so powerful a medicine; 

 and the dose should not exceed 10 grains or a scruple three times a day. An 



