OAK. 185 



durable ; their juice mixed with copperas and gum arabic makes 

 a good black ink. 



Qualities. — The bark is inodorous, with a rough, astringent 

 taste. It yields its virtues both to water and alcohol. The 

 aqueous infusion has a yellowish colour, and a weak styptic 

 taste ; the decoction has a brown colour, and the austere taste 

 of the bark. " It reddens tincture of litmus, and is pre- 

 cipitated by solutions of isinglass, infusion of yellow cinchona 

 bark, the carbonates of the alkalies, the aromatic spirits of 

 ammonia, lime-water, solutions of sulphate of iron, acetate of 

 lead, and bichloride of mercury.'' * Hence it contains gallic 

 acid, extractive and tannin, the latter in considerable quantity. 

 Sir H. Davy found that an ounce of the inner cortical part 

 of young oak bark afforded by lixiviation 111 grains of 

 solid matter, of which seventy-seven were tannin ; and the cel- 

 lular integument or middle coloured part yielded only forty- 

 three grains of solid matter, of which nineteen were tannin ; 

 and the epidermis furnished scarcely any tannin or extractive f . 



Medicinal Properties and Uses. — Every part of this tree 

 possesses a considerable degree of astringency ; but this pro- 

 perty is most abundant in the bark. Dioscorides and Galen, 

 with other ancient physicians, were fully aware of the qualities 

 of the Oak, and by them it was not infrequently prescribed in 

 dysentery, spitting of blood, and uterine haemorrhages, and from 

 Matthiolus, Lonicerus, and Horstius, we learn that it has also 

 been commended in fluor albus, gonorrhoea, tooth-ache, and 

 calculus J. Ledel found the bark boiled in beer useful in diar- 

 rhoea § ; and Darel || also gave the bark of the young branches 

 infused in wine for the same complaints. Like other astringents, 

 it has been used in intermittents % and some have supposed 



* Thomson's Dispensatory, 1830, p. 886. 



f Hence, for medical purposes the bark should be selected from the 

 smaller branches of the Oak, when the epidermis is still thin. The quan- 

 tity of tannin also varies considerably, according to the season of the year 

 at which the trees are barked ; thus the bark cut in spring contains, accord- 

 ing to Biggin, (Philos. Transactions, 1709,) four times more of the astringent 

 principle than that which is obtained in winter. 



+ Murray, App. Med. torn. i. p. 94. 



§ Ledel, Eph. N. Cur. Dec. 3. A. i. p. 88. 



|| Darel, Ap. p. 45. 



% Scopoli. Flor. Carn. p. 414. 

 VOL. II. O 



