MUSCULAR TISSUE 349 



with sand. Transfer to an evaporating dish, add water, and boil for 20 minutes. 

 Note the opalescence of the solution. At the boiling-point faintly acidify with 

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

 parts. Test one part 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? 



If difficulty is experienced in securing a satisfactory iodine test proceed 

 as follows: Make equal volumes of glycogen solution acid in reaction with 

 hydrochloric acid. Boil one solution to hydrolyze the glycogen. Add equal 

 volumes of iodine solution to each and note the more pronounced iodine reaction 

 in the unhydrolyzed solution. 



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



(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 bath-water at 4OC. 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, decant the supernatant fluid, 

 and filter the remainder. Heat the glycogen on a water-bath to remove the 

 alcohol, then subject it to the following tests : 



(a) Solubility. Try its solubility hi water and 10 per cent sodium chloride 

 solution. 



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



3. Testing for Inorganic Constituents. (a) Examination of Ash of Muscle. 

 Incinerate a small amount of muscular tissue, dissolve the ash in dilute hydro- 

 chloric acid. Test for potassium, phosphates, magnesium, calcium and chlorides. 



(b) Demonstration of Phosphates and Magnesium in Muscle (Hiirthle's 

 Experiment). Tease a very small piece of frog's muscle on a microscopical 

 slide. Expose the slide to ammonia vapor for a few moments, then adjust a 

 cover-glass, and examine the muscle fibers under the microscope. Note the 

 large number of crystals of ammonium magnesium phosphate, distributed every- 



NEU-0 



\ 

 Mg-O-P=O 



O 



where throughout the muscle fiber, thus demonstrating the abundance of phos- 

 phates and magnesium in the muscle (Fig. 129, page 408). 



