CELLULOSE. 11 



to a reducing sugar) in the liver after death by the action 

 of a ferment, making the test upon some liver from the 

 market. (Instead of this a part of the liver from Experi- 

 ment 14 can be used. This should be after it has stood 

 several hours in a warm place.) Chop it finely and extract 

 with boiling water. Acidify the solution slightly with 

 acetic acid, add a little sodium chlorid, and boil to pre- 

 cipitate the protein compounds. After filtering, test the 

 filtrate for glycogen by means of iodin and also for sugar 

 by Trommer's test. 



20. Add a little blood to a test-tube of the glycogen 

 solution and after it has stood ten minutes in a beaker of 

 water at body-temperature slightly acidify with acetic acid, 

 boil, and filter to remove the albumin, and test the filtrate 

 for glucose and glycogen. The latter has been converted 

 into glucose by a ferment which is found in the blood. 



CELLULOSE. 



Cellulose forms the membrane of the plant-cells, and 

 is not found as a constituent of the animal body, except in 

 a few of the lower forms. Cotton and filter-paper are two 

 of the most common examples. It is distinguished from 

 the other polysaccharids by its insolubility. It is insoluble 

 in the ordinary solvents, but can be dissolved in the strong 

 mineral acids, being converted into dextrin. It also dis- 

 solves in a solution of cupric hydrate in ammonia. 

 (Schweitzer's reagent), and in a solution of zinc chlorid 

 (Schultze's reagent). Sulphuric acid changes paper into a 

 parchment-like substance by covering the surface with a 

 coating of its decomposition-products and so sticking the 

 fibers together. Iodin does not stain the unaltered cellu- 

 lose, but does so after it has been acted upon by the acid. 



