Chemical Constituents of the Animal Body. 2 1 5 



Hydrolysis can also be brought about by means of the 

 ferment "diastase," which occurs in malt, saliva,* and 

 elsewhere. The degradation in this case does not proceed 

 as far as when acids are used, but other intermediate 

 products of the general formula 7i(C 6 H 12 6 ) (n 1)H 2 

 are produced, where n is a number smaller than the n of the 

 starch formula. In the case of maltose, which can be pro- 

 duced by diastase (see p. 213) ?i= 2. Other intermediate 

 products where n > 2 are also produced, such as the various 

 dextrins. A characteristic reaction for starch is the blue 

 colour which it gives on the addition of iodine (generally 

 added in when dissolved in a solution of potassium iodide). 

 As the starch is degraded by the action of the ferment, the 

 colour produced by the iodine reagent changes from blue 

 to purple and red, and finally disappears. The simplest 

 polysaccharoses, such as the maltose, give no coloration, 

 whereas the dextrins give brownish or reddish colorations. 



Glycogen is the animal starch, and is found in greatest 

 quantity in the livers of animals, especially after diets rich 

 in carbohydrates. It can be obtained by warming the 

 organs with strong solutions of potassium hydroxide, which 

 converts the proteins, etc., into soluble products, and then 

 adding alcohol to the mixture. The glycogen is thereby 

 precipitated. It soon disappears from the liver after the 

 death of the animal, as it undergoes hydrolysis into glucose 

 under the influence of the diastase contained in the organs. 

 Glycogen is a white powder, soluble in water, giving an 

 opalescent solution. It gives a red coloration with glucose. 



Cellulose is widely distributed throughout the vegetable 

 kingdom, and constitutes the framework of most vege- 

 table tissues. It is the chief constituent of linen, cotton, 

 hemp, and flax. The chemical character of the substances 

 included under the name of cellulose is still somewhat 



* The ferment in saliva is known as ptyalin. 



