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Gluten when burnt affords similar products to 

 albumen, and probably differs very little from it in 

 composition. Gluten is found in a great number of 

 plants ; Proust discovered it in acorns, chesnuts, 

 horse chesnuts, apples, and quinces ; barley, rye, peas 

 and beans j likewise in the leaves of rue, cabbage, 

 cresses, hemlock, borage, saffron, in the berries of 

 the elder, and in the grape. Gluten appears to be 

 one of the most nutritive of the vegetable substances ; 

 and wheat seems to owe its superiority to other grain, 

 from the circumstance of its containing it in larger 

 quantities. 



6. Gum elastic, or Caoutchouc, is procured from 

 the juice of a tree which grows in the Brazils, called 

 Ha^vea. When the tree is punctured, a milky juice 

 exudes from it, which gradually deposits a solid sub- 

 stance, and this is gum elastic. 



Gum elastic is pliable and soft like leather, and be- 

 ' comes softer when heated. In its pure state it is white ; 

 its specific gravity is 9335. It is combustible, and 

 burns with a white flame, throwing off a dense smoke, 

 with a very disagreeable smell. It is insoluble in wa- 

 ter, and in alcohol ; it is soluble in ether, volatile oils, 

 and in petroleum, and may be procured from ether in 

 an unaltered state, by evaporating its solution in that 

 liquid. Gum elastic seems to exist in a great variety 

 of plants : amongst them are, Jatropha elastica, Ficus 

 indica, Artocarpus integrifolia, and Urceola elastica. 



Bird-lime, a substance which may be procured 

 from the holly, is very analogous to gum elastic in its 

 properties. Species of gum elastic may be obtained 



