THE POLYSACCHARIDES. 73 



the most divers solvents, and are indeed soluble only in a solution 

 of cupric oxide in strong ammonia the so-called Schweitzer's 

 reagent. From this solution the substance can be obtained in 

 amorphous form on precipitation with acids. Moderately concen- 

 trated sulphuric acid transforms cellulose into vegetable amyloid, 

 which is colored blue by iodine. When the resulting esters of 

 cellulose and sulphuric acid are boiled in aqueous solution glucose 

 results. With concentrated nitric acid, or with a mixture of nitric 

 acid and concentrated sulphuric acid, it yields the highly explosive 

 nitrocellulose. 



Wood (lignin) and cork are derivatives of cellulose. 



On hydrolytic decomposition the common cellulose yields glucose, 

 while the so-called hemicelluloses give rise to galactose or mannose, as 

 also to certain pentoses, such as arabinose and xylose. In the intes- 

 tinal canal a certain portion of the ingested cellulose is unquestion- 

 ably dissolved. The products, however, to which it gives rise are for 

 the most part unknown. Certain micro-organisms which are present 

 at the time bring about a fermentation of the substance, during which 

 marsh gas, acetic acid, and butyric acid are formed, but the greater 

 portion no doubt is eliminated in the feces as such. 



Gums and Vegetable Mucins. Various kinds of gums occur 

 extensively distributed in the vegetable world, which on decomposi- 

 tion with dilute mineral acids yield galactose and arabinose. 

 Examples are gum arabic, cherry gum, the agar-agar which is 

 obtained from eastern Asiatic algae, etc. 



The vegetable mucins, unlike the gums, are more or less insoluble 

 in water. 



