PRACTICAL EXERCISES 627 



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 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-albuinin 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 myosinogen, 

 but not albumin, from its solutions ; saturation with ammonium sul- 

 phate precipitates both. Myosinogen is said to be dissolved 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 so'ution of a neutral salt (say 5 per cent, mag- 

 nesium sulphate). 



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

 on the inside of the dialyser 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 

 obtained with solutions of other proteids, such as albumin (Ramsden). 



Extracts in all essentials similar to those obtained from the muscles 

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

 into rigor. 



22. Eeaction of Muscle in Best, 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 normal saline solution at 40 to 

 42 C. It becomes rigid. The reaction becomes acid to litmus 

 paper, and also turns brown turmeric paper yellow. 



(c) Plunge another muscle into boiling normal saline solution. It 

 becomes harder than in (), and its reaction becomes acid to litmus 

 paper. 



(d) Stimulate another muscle with an interrupted current from 

 an induction machine (Fig. 65, p. 175), till it no longer contracts. 

 The reaction is now acid to litmus paper. Brewn turmeric paper 

 may also be turned yellow. 



40 2 



