2l6 



Biological Chemistry. 



uncertain. By the action of acids several derivatives of 

 considerable technical importance can be obtained, such as 

 gun-cotton, celloidin, celluloid, and the various artificial silks. 



In addition, a large number of other starch-like sub- 

 stances are found in plants, which give rise on hydrolysis 

 to sugars other than glucose. 



Inulin, which is found in certain plants, such as the 

 dahlia, yields on hydrolysis laevulose. 



Cherry -gum gives rise to arabinose (p. 210). 



Wood-gum gives rise to xylose. 



The mannans give rise to mannose. 



The vegetable gums and mucilages mostly appear to 

 be complex polysaccharoses, but their chemical constitu- 

 tions have not yet been definitely decided. 



ADDENDUM TO PART II. THE GLUCOSIDES. 



When dextrose is treated with methyl alcohol and 

 hydrochloric acid, two methyl derivatives known as a 

 and ft methyl glucosides are obtained, which may be 

 regarded as the simplest types of a large series of sugar 

 derivatives, many of which are found native in plants, 

 which are known as glucosides. The formulae assigned to 

 these substances are 



CH 3 CH\ CH OCH 3 



and 



CH 2 OH 

 a-Methyl Glucoside. 



/3-Methyl Glucoside, 



