336 MATER i A MEDIC A AND THERAPEUTICS. 



Substance resembling Oak Bark : Pale Cinchona Bark, which 

 is bitter. 



Composition. Oak bark contains 4 to 20 per cent of tannic 

 and gallic acids, pectin, and other constituents of plants. 



Incompatibles. Those of tannic and gallic acids. 



Preparation. 



Decoctum Quercus. 1 in 16. Dose, 1 in 2 fl.oz. Seldom 

 given internally. 



Oalla GALLS. Excrescences on Quercus infec- 

 toria, caused by the punctures and deposited ova of 

 Diplolepis Gallse tinctorise. 



Characters. Hard heavy globular bodies, varying in size 

 from half an inch to three-fourths of an inch in diameter, 

 tuberculated on the surface, the tubercles and intervening 

 spaces smooth; of a bluish-green colour on the surface, 

 yellowish- white within, with a small central cavity ; intensely 

 astringent. 



Composition. Galls contain from 15 to 65 per cent, of 

 tannic acid, about 5 per cent, of gallic acid, and other less 

 important constituents. 



Preparations. 



1. Tinctura Gallse. 1 in 8. Dose, % to 2 fl.dr. Seldom used 



except as a test. 



2. Unguentum Gallse. 1 in 6J. 



From Unguentum Gallce is prepared : 



Unguentum Gallas cum Opio. 1 of Opium to 14$ of Oint- 

 ment of Galls. 



from Galla are also made : 



1. Acidum Taniiicum. Tannic Acid. Tan- 

 nin. C 27 H 22 O 17 . An acid extracted from galls. 



Source. Made by exposing powdered galls to a damp 

 atmosphere ; macerating with ether ; pressing ; and 

 partially evaporating and drying the liquid portion. 



Characters. Pale yellow vesicular masses, or thin glisten- 

 ing scales, with a strong astringent taste, and acid 

 reaction. Solubility : 10 in 8 of water or spirit ; 

 sparingly in ether ; 1 in 3 of glycerine. 



Incompatibles. Gelatine (which it precipitates, distinguish- 

 ing it from gallic acid), mineral acids, alkalies ; 



