CYNIPS QUERCUS FOLII. 



and not used. So also are galls formed on other plants, by 

 beetles or other insects, of no medicinal use. 



Black or blue nutgalls ( Gallce nigrce seu ccerulece). Green 

 nutgalls ( Gallon virides) are called by the natives Yerli. They 

 vary from the size of a pea to that of a hazel-nut, and have 

 a grayish color. The smallest have a blackish-blue tint, and 

 are distinguished by the name of black or blue galls, while 

 the larger and greener varieties are called green galls. Ex- 

 ternally they are frequently tuberculated, but the surface of 

 the tubercles and of the intervening spaces is usually smooth. 

 Their texture is compact, but fragile. 



White galls (Gallce albce) are for the most part gathered 

 after the insect has escaped, and hence they are perforated 

 with a circular hole. They are larger, lighter colored (being 

 yellowish or whitish), less compact, less heavy, and less as- 

 tringent. 



TANNIN, TANNIC ACID, is a peculiar vegetable principle. It 

 receives its name, Tannin, from the circumstance of its form- 

 ing the principal agent in the operation of converting the 

 skins of animals into leather ; a process in which this princi 

 pie, as obtained from various astringent vegetables, is precip- 

 itated upon the gelatine of the skins from water in which it is 

 held in solution, and in which the skins, properly prepared, 

 are placed ; they are thus rendered impermeable to moisture, 

 and capable of resisting putrefaction under the ordinary cir- 

 cumstances which favor it in untanned animal matters. This 

 process is termed tanning ; hence the French chemists named 

 the principle on which it depends Tannin. It is an acid, and 

 is now named Tannic Acid. It is a component of most as- 

 tringent plants, and some diseased excrescences of such 

 plants, as, for example^ galls. 



CHEMICAL AND MEDICAL PROPERTIES AND USES. 



GALLS are nearly globular in their form, varying in size 

 from that of a pea to that of a large hazel-nut, and studded 

 with tuberosities ; they should be of a blackish-blue, or very 

 deep olive color, heavy, compact, brittle, breaking with a 

 flinty fracture, and their internal structure crystalline. They 

 yield the whole of their active matter to water, the residue 

 being inert and insipid. Alcohol and ether also take up a 

 considerable portion of the active principle. They contain a 



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