146 GUM. 



•wheat, wliicli is pressed out from a box through aper- 

 tures, which gives it its hollow form. The polenta 

 of the Italians is prepared by roasting maize when 

 the seed is only half ripe. 



334. There is a peculiar modification of starch 

 which exists in the tubers of the Jerusalem artichoke, 

 dahlia, and many similar plants, and is called inulin; 

 it contains a rather smaller proportion of carbon than 

 common starch does. 



335. Under the name of Gum are included several 

 substances, which differ considerably in their nature 

 and properties. They all agree in being tasteless, or 

 nearly so; but some dissolve readily in water, and 

 form a clear, transparent solution ; whilst others do 

 not dissolve, but merely soften and swell up in water, 

 forming a gelatinous mass. Gum Arabic is a good 

 example of the first kind, whilst common cherry-tree 

 gum belongs to the insoluble variety of gum. 



336. Gum is a natural exudation from many 

 plants, appearing on their surface in the form of 

 transparent drops or tears, which dry and harden in 

 the air. Most fruits contain a considerable quantity 

 of gum, and exudations of gum are frequently found 

 on many fruits, particularly the plum. There is a 

 peculiar substance resembling gum, to which the 

 name of pectine is given, and which exists in most 

 fruits ; it gelatinizes with water, and gives to fruits 

 the property which they have of forming imperfect 

 jellies. Black currant and apple jelly consists chiefly 



