402 HANDBOOK OF PHYSIOLOGY. 



corresponding to blood-serum. In the course of coagulation, therefore, 

 muscle plasma separates into muscle clot and muscle serum. The mus- 

 cle clot is the substance myosin. It differs from fibrin in being easily 

 soluble in a 2 per cent solution of hydrochloric acid, and a 10 per cent 

 solution of sodium chloride. It is insoluble in distilled water, and its 

 solutions coagulate on application of heat. It is a body, therefore, 

 belonging to the globulin class of proteids. During the process the re- 

 action of the fluid becomes distinctly acid. 



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

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

 certain proportions; for example, of sodium chloride, of magnesium sul- 

 phate, or of 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 neu- 

 tral salts if in strong solution. 



It is highly probable that the formation of muscle-clot is a ferment 

 action (myosin ferment). The antecedent of myosin in living muscle 

 has received the name of myosinogen, in the same way as the fibrin- 

 forming element in the blood is called fibrinogen. Myosinogen is, how- 

 ever, made up of two globulins, which coagulate at the temperatures 

 47 C. and 56 C. respectively. Myosin may also be obtained from dead 

 muscle by subjecting it, after all the blood, fat, and fibrous tissue, and 

 substances soluble in water have been removed, to a 10 per cent solution 

 of sodium chloride, or 5 per cent solution of magnesium sulphate, or 10 

 to 15 per cent solution of ammonium chloride, filtering and allowing the 

 filtrate to drop into a large quantity of water, when myosin separates out 

 as a white flocculent precipitate. 



A very remarkable fact with regard to the properties of myosin has 

 been demonstrated by Halliburton, namely, that a solution of muscle 

 which has undergone rigor mortis, in strong neutral saline solution, pos- 

 sesses very much the same properties as muscle plasma, and that if di- 

 luted with twice or three times its bulk of water, myosin will separate 

 out as a clot, which clot can be again dissolved in a strong neutral saline 

 solution, and the solution can be again made to clot on dilution. This 

 process can be often repeated; but in the fluid which exudes from the 

 clot there is no proteid present. Myosin then when dissolved in neutral 

 saline fluids is converted into myosinogen, but reappears on dilution of 

 the fluid. 



Muscle clot is almost pure myosin; but it appears to be combined 

 with a certain amount of salts, for if it be freed from salts, especially of 

 those of calcium, by prolonged dialysis, it loses its solubility. If a small 

 amount of calcium salts be added, however, it regains that property. 



Muscle serum is acid in reaction, and almost colorless. It contains 

 three proteid bodies, viz. (a.) A globulin (myo-globulin), which can be 



