THE VOLATILE PART OF PLANTS. 57 



ates as a solid in the form of spherical granules, which 

 may be identified with the aid of the microscope, and 

 have an evident crystalline structure. 



When long heated with water it is slowly but complete- 

 ly converted into a kind of sugar (levulose)*, hot dilute 

 acids accomplish the same transformation in a short 

 time. It is digested by animals, and doubtless has the 

 same value for food as starch. 



In chemical colnposition, inulin, dried at 213°, differs 

 from cellulose and starch by containing for six times 

 CeHjoOs, the elements of an additional molecule of water ; 

 C86He20so = 6 CeHioOj + H2O Eiliani. 



Levulin (C6Hio05)n coexists with inulin in the mature 

 or frozen tubers of the artichoke, dahlia, etc., and, accord- 

 ing to Muentz, is found in unripe rye-grain. It is a highly 

 soluble, tasteless, gum-like substance resembling dextrin, 

 but without effect on polarized light. It appears to be 

 formed from inulin when the latter is long heated with 

 water at the boiling point, or when the tubers contain- 

 ing inulin sproiit. Dilute acids readily transfonn it into 

 levulose, as they convert dextrin into dextrose. 



Glycogen (C6Hio05)n exists in the blood and mus- 

 cles of animals in small quantity, and abundantly in the 

 liver, especially soon after hearty eating. It is obtained 

 by boiling minced fresh livers with water, orw^eak potash 

 solution, and adding alcohol to the filtered liquid. It is 

 a white powder which, with water, makes an opalescent 

 solution. It is colored wine-red by iodine. Boiling di- 

 lute sulphuric acid converts it into dextrose. With saliva, 

 it is said to yield dextrin, maltose and dextrose. Accord- 

 ing to late observations, glycogen occurs in the vegetable 

 kingdom, having been identified in various fungi and in 

 plants of the flax and the potato families. 



The Gums and Pectin Bodies. — A number of 

 bodies exist in the vegetable kingdom, which, from the 

 similarity of their properties, have received the common 



