CHAPTER XV. 



MUSCULAR TISSUE. 



THE muscular tissues are divided physiologically into the vol- 

 untary (striated) and the involuntary (nonstriated). In the chem- 

 ical examination of muscular tissue the voluntary form is generally 

 employed. Muscle contains about 25 per cent .of solid matter, 

 of which about four-fifths is protein material and the remaining 

 one-fifth extractives and inorganic salts. 



The proteins are the most important of the constituents of mus- 

 cular tissue. In the living muscle we find two proteins, myosino- 

 gen and para-myosinogen. These may be shown to be present in 

 muscle plasma expressed from fresh muscles. In common with the 

 plasma of the blood this muscle plasma has the power of coagulat- 

 ing, and the clot formed in this process is called myosin. In the 

 onset of rigor mortis we have an indication of the formation of this 

 myosin clot within the body. The relation between the proteins 

 of living and dead muscle is represented graphically by Halliburton 

 as follows : 



Proteins of the living muscle. 

 /\ 



Para-myosinogen (25%). Myosinogen (75%). 



I 



Soluble myosin. 



Myosin. 

 (The protein of the muscle clot.) 



Of the total protein content of living muscle about 75 per cent 

 is made up by the myosinogen and the remaining 25 per cent is 

 para-myosinogen. These proteins may be separated by subjecting 

 the muscle plasma to fractional coagulation in the usual way. 

 Under these conditions the para-myosinogen is found to coagulate 

 at 47 C. and the myosinogen to coagulate at 56 C. It is also 

 claimed by some investigators that it is possible to separate these 

 two proteins by the fractional ammonium sulphate method, but 

 the possibility of making an accurate separation by this method 



235 



