THE PROPERTIES OF LIVING MUSCLE 471 



The relation between the proteins of living and dead muscle is represented 

 by Halliburton as follows: 



Proteins of the living muscle. 



Para-myosinogen. Myosinogen. 



Soluble myosin. 



Myosin. 

 (The protein of the muscle clot.) 



About 75 per cent, of the total protein content of living muscle is myo- 

 sinogen and the remaining 25 per cent, is para-myosinogen. These proteins 

 may be separated by subjecting the muscle plasma to fractional coagulation. 

 The para-myosinogen coagulates at 47 C. and the myosinogen at 56 C. 

 Para-myosinogen is a globulin since it responds to the precipitation tests of 

 this group of proteins and is insoluble in water. Myosinogen, on the contrary, 

 is not a typical globulin since it is soluble in water, but is a pseudo- globulin. 



Other Constituents of Muscle. In addition to muscle ferments 

 already mentioned, muscle contains certain proteolytic enzymes, as do 

 other tissues, an amylolytic ferment, a maltase, and a lactic-acid forming 

 enzyme. 



Certain acids are also present, particularly sarco-lactic acid. 



Of carbohydrates, glycogen and dextrose are present. Glycogen is 

 present in considerable amount, especially in the muscles of w T ell-nourished 

 animals. 



Nitrogenous crystalline bodies, such as creatin, creatinin, xanthin, hypo- 

 xanthin, carnin, guanin, urea in very small amount, uric acid, and inosinic 

 and phospho-carnic acids, are all found on extracting dead muscle. 



Chlorides and salts of potassium, calcium, magnesium, and iron are 

 present in muscle, the chief of which is potassium phosphate. 



In extracts of muscles, especially of red muscles, there is a certain amount 

 of hemoglobin, and also of a pigment special to muscle, called by McMunn 

 myo-hematin, which has a spectrum quite distinct from hemoglobin, viz., a 

 narrow band just before D, two very narrow bands between D and E, and 

 two other faint bands, near E b, and between E and F close to F. 



Fats occur in the connective tissue around and between the muscle 

 fibers, and lipoids and fat droplets also are present within the individual 

 muscle fibers. 



THE PROPERTIES OF LIVING MUSCLE. 



Elasticity. Muscle has a certain amount of elasticity during rest. 

 It admits of being considerably stretched, but returns readily and completely 



