176 THE CHEMISTRY OF SOME FOODS. [CH. VIK 



Non-nitrogenous extractives. Glycogen. 



Sarcolactic acid. 



Inorganic. Water. 



Salts, chiefly potassium and magnesium 

 phosphates. 



The proteins of living muscle are mainly myosinogen 

 (80 per cent.) and paramyosinogen (20 per cent.). The 

 former is an albumin, coagulating at 57 C. The latter is 

 a globulin, coagulating at 47 C. 



On standing or on treatment with dilute acids they 

 are converted into myosin the protein of dead muscle. In 

 this transformation, myosinogen passes through an inter- 

 mediate stage of soluble myosin which coagulates at 40 C. 



Myosinogen. Paramyosinogen. 



Soluble myosin. 

 Myosin. 



213. Preparation o! fresh muscle extract. A rabbit is 

 killed, a cannula fixed into the aorta and an opening made in the 

 right auricle. The vessels are then washed free from blood with 

 0-9 per cent, sodium chloride. The muscles of the limbs are removed, 

 rapidly minced and treated with ice-cold 5 per cent, magnesium 

 sulphate, and the mixture left in the ice chest for about 24 hours. 

 The extract is filtered and the following tests performed with it : 



214. Take the reaction to litmus. It is generally neutral. 



215. Dilute a small portion with four volumes of distilled 

 water and leave the tube in the water bath at 37 C. for some time, 

 A clot of myosin forms, leaving muscle serum. 



216. Take the reaction of the muscle serum to litmus. It is 

 distinctly acid, due to the production of sarcolactic acid. 



217. Add some acetic acid to another portion of the extract. 

 A precipitate of myosin occurs immediately. 



