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30 GOODYEAR ON G UM- E L AS T I C . 



GUM LAC OR SHELLAC. 



This gum, is now rapidly assuming that degree of importance 

 in relation to the perfection of the Inventions treated of in this 

 work, that it is deemed worthy of particular notice, in connec- 

 tion with the history of India rubber. 



The following account of it is taken from the "United States 

 Dispensatory." 



" It is a resinous substance obtained from several trees grow- 

 ing in the East Indies, particularly from the Croton lacciferurn, and 

 two species of Ficus, the F. religiosa and F. Indica. It is found 

 in the form of a crust surrounding the twigs or extreme branches, 

 and is generally supposed to be an exudation from the bark, 

 owing to the puncture of an insect belonging to the genus Coc- 

 cus, and denominated C. Lacca. By some it is thought to be 

 an exudation from the bodies of the insects themselves, which 

 collect in great numbers upon the twigs, and are imbedded in the 

 concreted juice, through which the young insects eat a passage 

 and escape. Several varieties are known in commerce. The 

 most common are stick lac, seed lac, and shell lac. 



" Stick lac is the resin as taken from the tree, still incrusting 

 the small twigs around which it originally concreted. It is of a 

 deep reddish brown color, of a shining fracture, translucent at 

 the edges, inodorous, and of an astringent, slightly bitterish 

 taste. Its external surface is perforated with numerous minute 

 pores, as if made by a needle ; and when broken it exhibits 

 many oblong cells, often containing the dead insect. When 

 chewed, it colors the saliva beautifully red ; and when burnt, 

 diffuses a strong agreeable odor. It is in great measure soluble 

 in alcohol. 



"Seed lac consists of minute irregular fragments broken from 

 the twigs, and partially exhausted by water. It is of a light or 

 dark brown color, inclining to red or yellow, feebly shining, 

 almost tasteless, and capable of imparting to water less color 



