SECT. XVI. GUM-RESINS. 43Q 



Such are the most remarkable of the resins that 

 have hitherto been subjected to chemical analysis, 

 or employed in medicine and the arts. Their me- 

 dical virtues, however, are not quite so great as has 

 been generally supposed ; but their utility in the 

 arts is very considerable. They are employed in 

 the arts of painting, varnishing, embalming, and 

 perfumery ; and they furnish us with two of the 

 most important of all materials to a naval power, 

 pitch and tar. 



SECTION XVI. 



Gum-resins. 



THIS term is employed to denote a class of ve- Whence 

 getable substances which have been regarded by 

 chemists as consisting of gum and resin. They are 

 generally contained in the proper vessels of the 

 plant, whether in the root, stem, branches, leaves, 

 flower, or fruit. But there is this remarkable dif- 

 ference between resins and gum-resins, that the 

 latter have never been known, like the former, to 

 exude spontaneously from the plant.* They are 

 obtained by means of bruising the parts con- 

 taining them, and expressing the juice, which is 

 always in the state of an emulsion, generally 

 white, but sometimes of a different colou- ; or they 

 are obtained by means of incisions from which the 



* Fourcroy, vol. viii. p. 27 



