On the coagulation of muscle plasma. II.―The solubility of myosin

It is a matter of some importance in the physiology of muscle whether myosin, the water-insoluble globulin of muscle, is in the dispersed (sol) or solid (gel) state, and whether it is capable under physiological conditions, such as during contraction or in rigor mortis of changing from one state to the other. The fact of the coagulation of muscle plasma, discovered by Kühne, would suggest that the proteins are present in the soI form, but it was shown in a previous paper (smith, 1930) that it is necessary to add neutral salt to the muscle before a coagulable plasma can be expressed. A more precise study has now been made of the conditions which affect the dispersion of myosin, and the results suggest that in living muscle not more than 10% of the myosin is dispersed. In the preparation of muscle plasma freezing and/or the addition of salt are required to liquefy the remaining 90% so that the plasma may be expressed. The subsequent clotting of this expressate is of no physiological significance. It is probably due to admixture of the salt plasma with water formed from the melting muscle snow. The important fact to which these experiments draw attention is the probable necessity of finding an explanation of rigor mortis in terms of changes in gel structure rather that in terms of the precipitation of a dispersed colloid.