244 PHYSIOLOGICAL CHEMISTRY. 



(b) Place a little of the solution in a test-tube and heat to boiling. 

 At the boiling-point add a drop of dilute acetic acid and filter. Test 

 this filtrate for proteose with picric acid. Is any proteose present? 

 Saturate another portion of the filtrate with ammonium sulphate 

 and test for peptone in the usual way (see page 114). Do you 

 find any peptone? From your experiments on "living" and 

 " dead " muscle what are your ideas regarding the proteins of 

 muscle ? 



2. Preparation of Glycogen. Grind a few scallops in a mor- 

 tar with sand. Transfer to an evaporating dish, add water and 

 boil for 20 minutes. At the boiling-point faintly acidify with 

 acetic acid. Why is this acid added ? Filter, and divide the filtrate 

 into two parts. Note the opalescence of the solution. Test one 

 portion of the filtrate as follows : 



(a) Iodine Test. To 5 c.c. of the solution in a test-tube add 

 5-10 drops of iodine solution and 2-3 drops of 10 per cent sodium 

 chloride. What do you observe? Is this similar to the iodine test 

 upon any other body with which we have had to deal ? 



(b) Reduction Test. Does the solution reduce Fehling's solu- 

 tion? 



(c) Hydrolysis of Glycogen. Add 10 drops of concentrated 

 hydrochloric acid to 10 c.c. of the solution and boil for 10 minutes. 

 Cool the solution, neutralize with solid potassium hydroxide and 

 test with Fehling's solution. Does it still fail to reduce Fehling's 

 solution? If you find a reduction how can you prove the identity 

 of the reducing substance? 



(d) Influence of Saliva. Place 5 c.c. of the solution in a test- 

 tube, add 5 drops of saliva and place on the water-bath at 40 C. 

 for 10 minutes. Does this now reduce Fehling's solution? 



To the second part of the glycogen filtrate add 3-4 volumes of 

 -95 per cent alcohol. Allow the glycogen precipitate to settle, de- 

 cant the supernatant fluid, filter the remainder and upon the glyco- 

 gen make the following tests : 



(a) Solubility. Try its solubility in the ordinary solvents. 



(b) Iodine Test. Place a small amount of the glycogen in a de- 

 pression of a test-tablet and add 2-3 drops of dilute iodine solution 

 and a trace of a sodium chloride solution. The same wine-red 

 color is observed as in the iodine test upon the glycogen solution. 



