MUSCULAR TISSUE 367 



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 hi 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 in 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- 



NH 4 -O 



\ 

 Mg-0-P=O 



\/ 

 



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

 phates and magnesium hi the muscle (Fig. 134, page 426). 



Separation of Extractives from Muscles 



i. Creatine. Dissolve about 10 grams of a commercial extract of meat hi 

 200 c.c. of warm water. (Test for Protein by Biuret and Coagulation Tests, see 

 Chapter V.) Precipitate the inorganic constituents by neutral lead acetate, 

 being careful not to add an excess of the reagent. Write the equations for the 

 reactions taking place here. Allow the precipitate to settle, then filter and remove 

 the excess of lead in the warm filtrate by hydrogen sulphide. Filter while the solu- 

 tion is yet warm, evaporate the clear filtrate to a syrup, and allow it to stand at 

 least 48 hours in a cool place. Crystals of creatine should form at this point. 

 Examine under the microscope (Fig. 115, page 360). Treat the syrup with 200 



