CHAPTER XX 

 MUSCULAR TISSUE 



THE muscular tissues are divided physiologically into the voluntary 

 (striated) and the involuntary (non-striated or smooth). In the 

 chemical examination of muscular tissue the voluntary form is gener- 

 ally 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 muscular 

 tissue. In the living muscle we find two proteins, myosinogen 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 coagulating, and the clot 

 formed in this process is called myosin. According to Halliburton 1 

 and others in the onset of rigor mortis we have an indication of the for- 

 mation of this myosin clot within the body. The relation between the 

 proteins of living and dead muscle is represented graphically by Halli- 

 burton as follows: 



Proteins of the living muscle. 



I I 



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



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 47C. 

 and the myosinogen to coagulate at 56C. 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 



1 Halliburton: Biochemistry of Muscle and Nerve, 1904, p. 4. 



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