348 PHYSIOLOGICAL CHEMISTRY 



Insert a small wire hook through the jaws of the frog and suspend the animal 

 from an ordinary clamp or iron ring. Pass electrodes under the exposed 

 sciatic nerve, and after tying the other leg to prevent any muscular movement, 

 stimulate the exposed nerve by means of make and break shocks from an in- 

 duction coil. The stimulated leg responds by pronounced muscular contrac- 

 tions, whereas the tied leg remains inactive. Continue the stimulation until 

 the muscles are fatigued. The muscular activity has caused the production of 

 lactic acid and this in turn -has reacted with the injected fuchsin to cause a pink 

 or red color to develop. The muscles of the inactive leg still remain unchanged 

 in color. 



The normal color of the Fuchsin "S" when injected was red, but upon being 

 absorbed it became colorless through the action of the alkalinity of the blood. 

 Upon stimulating the muscles, however, as above explained, lactic acid was formed 

 and this acid reacted with the fuchsin and again produced the original color of 

 the dye. 



II. Experiments on "Dead" Muscle 



1. Preparation of Myosin. Take 25 grams of finely divided lean beef 

 which has been carefully washed to remove blood and lymph constituents and 

 place it in a beaker with 10 per cent sodium chloride. Stir occasionally for 

 several hours. Strain off the meat pieces by means of cheese cloth, filter the 

 solution and saturate it with sodium chloride in substance. Filter off the pre- 

 cipitate of myosin and make the tests as given below. This nitration will pro- 

 ceed very slowly. Myosin collects as a film on the sides of the filter paper and 

 may be removed and tested before the entire volume of fluid has been filtered. 

 If this precipitate remains for any length of time on the paper in contact with the 

 air it will become transformed into the protean myosan. Test the myosin pre- 

 cipitate as follows : 



(a) Solubility. Try its solubility in water, sodium chloride, dilute acid and 

 alkali. Is myosin an albumin or a globulin? 



(b) Xanthoproteic Reaction. See page 98. 



(c) Coagulation Test. Suspend a little of the myosin in water in a test- 

 tube and heat to boiling for a few moments. Now remove the suspended ma- 

 terial and try its solubility in 10 per cent sodium chloride. What property does 

 this experiment show myosin to possess? 



Test the filtrate from the original myosin precipitate as follows : 



(a) Biuret Test. What does this show? 



(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 120). 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 oysters or scallops 1 in a mortar 



1 Glycogen may also be prepared from the liver of an animal which has been fed a high 

 carbohydrate diet for 1-2 days previously. The best yield of glycogen can, however, gen- 

 erally be obtained from scallops. To secure best yield of glycogen the liver, scallops or 

 oysters should be fresh. If permitted to stand some glycogen will be converted into 

 glucose. 



