THE POLYSACCHAR1DES. 59 



As stated, it does not yield an osazon and does not reduce metal- 

 lic oxides. After inversion with invertin it undergoes the same 

 fermentations as the resulting monosaccharides. On oxidation 

 it yields, in addition to other substances, saccharinic and oxalic 

 acids. 



Maltose does not occur in nature as such, but results during the 

 digestion of starch and glycogen in the alimentary canal. 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 under- 

 goes fermentation, and like glucose reduces metallic oxides in alka- 

 line solution, but to a less degree. 



Isomaltose results from starch through the action of a diastatic 

 ferment. In the intestinal canal it is thus found together with 

 maltose. It is easily soluble in water and turns the plane of polari- 

 zation to the right. Its osazon melts at 150 to 153 C. It under- 

 goes fermentation, but much more slowly than maltose. 



Lactose, which is almost exclusively found in the animal world, 

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



THE POLYSACCHARIDES. 



The 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 (CgHjoO^, in which x is a vari- 

 able factor, but exceeds two. In many cases 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 in this case is equivalent to 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 

 to maltose, which finally yields glucose. In other cases, as with 

 glycogen, the disaccharides isomaltose and maltose are formed 

 directly. Cellulose likewise yields glucose as a final product, while 

 Isevulose results from inulin, and mannose from the so-called reserve 

 celluloses, which are found in the cell- walls of many seeds. Galac- 

 tose is similarly obtained from many gums, and from a variety 

 of cellulose, which Schultze has termed galactose-cellulose, in con- 

 tradistinction to the mannose-cellulose and the true dextrose-cellu- 

 loses. In many instances, however, the exact mode of decomposi- 



