PRACTICAL EXERCISES 715 



is still some precipitate at 47 to 50. Paramyosinogen possesses 

 some of the characters of both globulins and albumins, for it is 

 partially but not entirely precipitated by saturation with magnesium 

 sulphate, and is not precipitated by sodium chloride. 



(2) (a) Test the reaction of the magnesium sulphate extract. It 

 will usually be faintly acid to litmus. 



(b) Heat some of it. Precipitates will be obtained at the same 

 temperatures as in (i) (b), but those at 47 to 50 and 56 to 58 will 

 be more abundant. Of the two, that at 47 to 50 will usually be 

 the larger when time is given for it to come down and the heating is 

 gradual. 



(c) Dilute some of the magnesium sulphate extract with three 

 times, another portion with four times, and another with five times, 

 its volume of water in a test-tube, and put in a bath, at 40 C. 

 Coagulation or precipitation will occur in one or all of these test-tubes. 

 To another test-tube of the extract diluted in the proportion which 

 has given the best ' muscle-clot ' add a few drops of a dilute solution 

 of potassium oxalate, and place in the bath at 40. Coagulation 

 occurs as before. Filter off the clot from all the test-tubes. The 

 filtrate is the ' muscle-serum,' and yields a precipitate of serum- 

 albumin at 70 to 73 C. 



(3) Myosinogen, like other globulins, is insoluble in distilled water, 

 but soluble in weak saline solutions. Saturation with neutral salts 

 like sodium chloride and magnesium sulphate precipitates myo- 

 sinogen, but not albumin, from its solutions ; saturation with ammo- 

 nium sulphate precipitates both. Myosinogen is said to be dis- 

 solved without change in very weak acids. Stronger acids precipitate 

 it. Verify the following reactions of myosinogen, using the original 

 magnesium sulphate extract of the muscle. 



(a) Dropped into water, it is precipitated in flakes, which can be 

 redissolved by a weak solution of a neutral salt (say 5 per cent, 

 magnesium sulphate). 



(b) When a solution of myosinogen is dialyzed, it is precipitated 

 on the inside of the dialyzer as the salts pass out. 



(c) If a piece of rock-salt is suspended in a solution, the myosin 

 gradually gathers upon it, diffusion of the salt out through the pre- 

 cipitated myosin always keeping a saturated layer around it. 



(d) Saturate a solution containing myosinogen with crystals of 

 magnesium sulphate, stirring or shaking at frequent intervals. The 

 myosinogen is precipitated. 



(e) Without adding any salt, simply shake a myosinogen solution 

 vigorously ; a certain amount of the myosinogen will be precipitated, 

 and the solution will become turbid. This reaction can also be ob- 

 tained with solutions of other proteins, such as albumins (Ramsden). 



Extracts qualitatively similar to those obtained from the muscles 

 of a freshly-killed animal can be got from muscles that have entered 

 into rigor, but the quantity of the various proteins going into solution 

 is less. 



19. Reaction of Muscle in Rest, Activity, and Rigor Mortis. 

 (a) Take a frog's muscle, cut it across, and press a piece of red 

 litmus-paper on the cut end ; it is turned blue. Yellow turmeric 

 paper is not affected. 



(b) Immerse another muscle in physiological salt solution (0-75 

 per cent, for frog's tissues) at 40 to 42 C. It becomes rigid. The 

 reaction becomes acid to litmus -paper, and also turns brown turmeric 

 paper yellow. 



