CHAPTER XIII. 

 MUSCLE-NERVE PHYSIOLOGY. 



The structure of muscle, of nerve, and of nerve relations to muscle are 

 all given in considerable detail in Chapter II, to which the reader is referred 



CHEMICAL COMPOSITION OF MUSCLE. 



Muscle Plasma. The principal substance which can be extracted 

 from muscle, when examined after death, is the protein body, myosin. 

 This body appears to bear somewhat the same relation to the living muscle 

 that fibrin does to the living blood, since the coagulation of muscle after 

 death is due to the formation of myosin. Thus, if coagulation be delayed 

 by removing the muscles immediately that an animal is killed, and rapidly 

 cooling them to a temperature below o C. before the muscles themselves 

 lose their irritability, it is possible to express a viscid fluid of slightly alkaline 

 reaction, called muscle plasma (Kiihne). Muscle plasma, if exposed to 

 the ordinary temperature of the air, undergoes coagulation much in the same 

 way as does blood plasma under similar circumstances when separated 

 from the blood corpuscles at a low temperature. The appearances presented 

 by the fluid during the process are also very similar to the phenomena of 

 blood-clotting, viz., first of all an increased viscidity appears on the surface 

 of the fluid, and at the sides of the containing vessel, which gradually extends 

 throughout the entire mass, until a fine transparent clot is obtained. In the 

 course of some hours the clot begins to contract, and to squeeze out of its 

 meshes a fluid corresponding to blood serum. In the course of coagulation, 

 therefore, muscle plasma separates into muscle clot and muscle serum. The 

 muscle clot contains the substance myosin. It differs from fibrin in being 

 easily soluble in a 10 per cent, solution of sodium chloride. It is insoluble 

 in distilled water, and its solutions coagulate on application of heat; in short, 

 it is a globulin. During the process of clotting the reaction of the fluid 

 becomes distinctly acid. 



The coagulation of muscle plasma can be prevented not only by cold, 

 but also, as Halliburton has shown, by the presence of neutral salts in certain 

 proportions; for example, of sodium chloride, magnesium sulphate, or sodium 

 sulphate. It will be remembered that this is also the case with blood plasma. 

 Dilution of the salted muscle plasma will produce slow coagulation. 



It is highly probable that the formation of muscle clot is due to the 

 presence of a ferment, myosin ferment. 



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