THE VOLATILE PART OF PLANTS. 71 



Marcker & Kobus made comparative analyses of well-cured and of 

 sprouted barley, with the following results per cent: 



Sound. Grown. 



Starch 64.10 57.98 



Soluble starch 1.76 1.17 



Dextrin 1.10 0.00 



Dextrose 0.00 4.92 ' 



Maltose 3.12 7.92 



The various gums are a result of the transformation of 

 cellulose, as Mohl first showed by microscopic study. 



b. In the animal, the substances we have been describ- 

 ing also suffer transformation when employed as food. 

 During the process of digestion, cellulose, so far as it is 

 acted upon, starch, dextrin, and probably the gums, are 

 all converted into dextrose or other sugars, and from 

 these, in the liver especially, glycogen is formed. 



c. Many of these changes may also be produced apart 

 from physiological agency, by the action of heat, acids, 

 and ferments, operating singly or jointly. 



Cellulose and starch are converted, by boiling with a 

 ililute acid, into amidulin, dextrin, maltose and dextrose. 

 Cellulose and starch acted upon for some time by strong 

 nitric acid give compounds from which dextrin may be 

 separated. Cellulose nitrate sometimes yields gum (dex- 

 trin) by its spontaneous decomposition. A kind of gum 

 also appears in solutions of cane-sugar or in beet-juice, 

 when they ferment under certain conditions. Inulin and 

 the gums yield glucoses, but no dextrin, when boiled 

 with weak acids. 



d. It will be noticed that while physical and chemical 

 agencies produce these metamorphoses mostly in one di- 

 rection, under the influence of life they go on in either 

 direction. 



In the laboratory we can in general only reduce from a 

 higher, organized, or more complex constitution to a 

 lower and simpler one. In the vegetable, however, all 

 these changes, take place with the greatest facility. 



The Chemical Composition of the Carbhydra/tes. It 



