THE CARBOHYDRATES. 



DEXTRIN. 



Dextrin is the intermediate product in the change from 

 starch to glucose or maltose. There have been several 

 varieties described: erythrodextrin, which is colored red 

 by iodin; achroodextrin, which is not so colored, etc. 



It is formed from starch by the action of heat, acids, 

 or ferments. It is soluble in water, making a sticky liquid, 

 often used for a mucilage. It is produced when bread is 

 toasted, and is also found in the crust. Toast or bread- 

 crust, then, has its starch partially changed into a more 

 diffusible substance. 



13. Prepare dextrin from starch by heating in a porcelain 

 dish on a sand-bath half a spoonful of powdered starch previously 

 dampened with a few drops of dilute nitric acid (made by adding 

 a few drops of nitric acid to a test-tubef ul of water) . The starch 

 must be stirred with a glass rod until it has turned yellowish or 

 brown, when it has been changed to dextrin. 



14. Dissolve some dextrin in water and test with a 

 drop of iodin solution. A red or brown color is produced, 

 not a blue, if the change has been complete. If commer- 

 cial dextrin is tested it will probably be found to contain 

 undecomposed starch. 



GrLYCOGEN. yit 



Glycogen is found in a few of the lower plants, in some 

 shell-fish, and in many fluids and tissues of the bodies of 

 mammals. It is most abundant in the liver, and next in 

 the muscles. It is also called liver-sugar or liver-starch. 

 In the animal body it is most plentiful when the animal is 

 well nourished, especially after a full meal. At such times 

 it may be in as large an amount as 10 or 12 per cent, of 



