380 PJiysical Chemistry of Muscle Plasma [April 



microscopic granules was never observed before; this is the most 

 important result of my investigations. 



The number or concentration of the granules in the original 

 plasma is so great that the iiltramicroscopic field appears almost 

 uniformly luminous — the individual granules cannot be distinctly 

 Seen. But when the plasma is diluted with Ringer Solution, the 

 granules are separated, and then appear as distinct brilliant cor- 

 puscles endowed with lively Brownian movements on a darkish 

 homogeneous background. They are not precipitation-particles of 

 a dissolved muscle protein, because they do not disappear under the 

 action of dilute alkali. Precipitation of such protein might be 

 caused by lactic acid produced in the muscles, but in that case the 

 particles would be dissolved by alkali — we do not know of any acid- 

 precipitated proteins that are not resoluble in alkalies. No ordinary 

 reagent causes the granules to disappear at a low temperature. 

 Moreover, acid increascs the number of particles, by precipitating a 

 special dissolved muscle protein. 



The granules are present in almost equal number in plasmas ex- 

 pressed from muscles which have been cooled to a low degree and 

 which, therefore, are non-irritant, t. e., from muscles in which acid 

 production is greatly diminished. The concentration of the granules 

 is greater in the plasma of striated muscle than in that of piain 

 muscle. 



Normal muscle plasma is, then, a Suspension of ultramicroscopic 

 granules in a liquid zvhich, besides containing mineral salts and ex- 

 tractives, certainly holds protein in a state of true Solution. Ac- 

 cordingly, the plasma, f reed from the granules, is an optically homo- 

 geneous fluid, but on adding to it a weak acid Solution, or on 

 heating it at 55° C, additional particles appear — true precipitation- 

 particles of a dissolved muscle protein, which may be termed myo- 

 protein, while we may give the name myosin to the protein of which 

 the plasma granules are made. The existence of other muscle pro- 

 teins in the muscle plasma has not been proved. 



The observed plasma granules are apparently a degradation or 

 cleavage product of material in the myofibrils, piain or striated, and 

 preexist in all muscle plasma. Their preexistence is not only easily 

 conceivable, but we are also obliged to assume it, when we reflect 



