CHAPTER XIII 



MUSCLE-NERVE PHYSIOLOGY 

 CHEMICAL COMPOSITION OF MUSCLE 



Muscle Plasma. The principal substance which can be extracted 

 from muscle, when examined after death, is the proteid body, myosin, some 

 of the reactions of which have been already discussed. 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 from them a viscid fluid of slightly alkaline reaction, 

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

 the ordinary temperature of the air (or more quickly at 37 to4oC.), undergoes 

 coagulation much in the same way as does blood plasma under similar cir- 

 cumstances 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, un'il 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 2 per cent solution 

 of hydrochloric acid, and 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 its slow coagulation, which 

 is prevented by the presence of the neutral salts in strong solution. 



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