70 THE CARBOHYDRATES. 



abundantly in sugar-cane, in the roots of the sugar beet, and in the 

 juices of various trees (palms, sugar maple, birch, etc.). In the 

 animal organism it does not occur. The pure substance is crystalline, 

 and melts at 160 C. On further heating it turns brown and forms 

 so-called caramel. It is easily soluble in water and turns the plane 

 of polarization to the right. As stated, it does not yield an osazon 

 and does not reduce metallic oxides. After inversion with invertin 

 it undergoes the same fermentations as the resulting monosacchar- 

 ides. On oxidation it yields, in addition to other substances, 

 saccharinic and oxalic acids. 



Maltose (maltobiose, ptyalose, cerealose) does not occur in nature 

 as such, but results during the digestion of starch and glycogen in the 

 alimentary canal through the action of diastase. It is a crystalline 

 substance, which is easily soluble in water and turns the plane of 

 polarization to the right. With phenylhydrazin it yields an osazon 

 maltosazon which melts at 206 C. It readily undergoes 

 fermentation, and like glucose reduces metallic oxides in alkaline 

 solution, but to a less degree. 



An isomaltose results from starch through the action of a dias- 

 tatic ferment. It is also formed (synthetically) by the maltoglucase 

 of yeast and the taka-diastase of Aspergillus oryzse from glucose. In 

 the intestinal canal it is found together with maltose. It is easily 

 soluble in water and turns the plane of polarization to the right. 

 Its osazon melts at 150 to 153 C. It undergoes fermentation, but 

 much more slowly than maltose. 



Lactose (lactobiose), which is almost exclusively found in the 

 animal world, will be considered in a subsequent chapter (see Milk). 



An isolactose is formed (synthetically) as a result of the action 

 of the lactoglucase of kefir upon a mixture of glucose and galactose. 



THE POLYSACCHARIDES. 



The higher polysaccharides result from the monosaccharides in the 

 same way as the disaccharides. In other words, they represent the 

 anhydrides of the monosaccharides, of which many molecules, how- 

 ever, are condensed to form the resulting polysaccharine molecule. 

 Their general formula therefore is (C 6 H 10 O 5 ) r . The value of x is 

 unknown, but it is probably always large. From a determination 

 of the size of the starch molecule, for example, we may conclude 

 that x is equivalent to at least 108. In others, such as glycogen 

 and the dextrins, however, it is certainly much smaller. In con- 

 formity with their structure, the polysaccharides all yield mono- 

 saccharides on hydrolytic decomposition. During this process, 

 however, a variable number of intermediary products are formed, 

 which may themselves be polysaccharides, though of a lower order, 

 and which in turn yield disaccharides and finally monosaccharides. 

 Starch is thus first transformed into erythrodextrin, which in turn 

 yields achroodextrin ; this is further changed to isomaltose, and then 



