68 MATERIA MEDIC A. 



very soluble in water, alcohol, and eiher, and of an entirely astrin- 

 gent taste. Incojiijmtibles, — mineral acids, alkalies, vegetable alka- 

 lies, the sesquisalts of iron, and gelatine. Acts on the system as a 

 pure astringent ; useful in diarrhoea and some forms of local hemor- 

 rhage. Dose, 3 grs., three or four times a day. 



VEGETABLE ASTRINGENTS. 



Oak Bark. — (Quercus, U. S.) 



The only officinal varieties of the oak, are the Q. alba^ or white 

 oak, and Q. tinctoria, or black oak ; though other species may con- 

 tribute to furnish the shops. White oak bark is recognised by its 

 whitish epidermis and superficial furrows ; internally, it has a light 

 brown colour and fibrous texture; tasie, bitter and astringent; does 

 not tinge the saliva. Black oak bark is darker coloured externally, 

 more deeply furrowed, has a more bitter taste, and imparts a yellow 

 colour to the saliva in consequence of its containing a peculiar prin- 

 ciple, quercitrine : this principle renders the black oak bark valuable 

 as a dye. Both impart their virtues to water and alcohol. They 

 contain tannic and gallic acids. Not much used internally. The 

 white is astringent ; the black frequently purges from the irritation it 

 causes. Oak bark is employed externally in the form of bath, for 

 marasmus, or chronic diarrhoea ; also as a lotion, or poultice, to in- 

 dolent and gangrenous ulcers. Dose, of powder, 30 grs. ; of the 

 decoction, f 3ij ; of the extract, 10 to 20 grs. The oak leaves and 

 acorns are also astringent. 



Galls. — (Galla, U. S.) 



Excrescences produced by the puncture of an insect upon the 

 young twigs of the Quercus injector ia^ a native of Asia Minor. The 

 market is chiefly supplied from the ports of the Levant ; they are 

 named Aleppo galls. There are two varieties, the blue and the 

 white ; the former are the smallest, most compact, and most valuable ; 

 the latter are of a yellowish-brown hue, lighter, and have a perfora- 

 tion which indicates that the insect which they contained has made 

 its escape. The blue galls are to be preferred ; they have a flinty 

 fracture, no odour, a bitter and very astringent taste, yield their 

 virtues to water and alcohol ; they contain much tannic and gallic 

 acids. Incompatibles, the same as of tannin. 



Uses. — Chiefly externally, in the form of decoction, as a gargle or 

 lotion ; also as an ointment {iinguent. gaUce), for piles. Dose of 

 powder, 10 to 20 grs.; of the decoction, fjij. 



The syrup is used in chronic diarrhoea. 



Kino, U. S. 

 An extract, or an inspissated juice, of certain trees. Several 



