SKELETAL MUSCLE. 97 



does cold prevent the coagulation of muscle plasma, but, as in the case of 

 blood plasma, admixture with solutions of neutral salts has the same 

 effect. Addition of water to the salted muscle plasma brings about 

 coagulation (an acid reaction making its appearance simultaneously), 

 especially at 40 C., and still more rapidly if solution of " myosin 

 ferment " is added. The myosin ferment was prepared from muscle 

 in the same way as fibrin ferment from blood serum. 



Saline extracts of muscle which has undergone rigor mortis, resemble 

 salted muscle plasma very closely ; after dilution they undergo coagula- 

 tion; this may be a re-coagulation of the redissolved myosin, for the 

 acidity of the saline extract is increased by re-coagulation. Some 

 observers, however, regard this phenomenon not as a true re-coagulation, 

 but as a simple precipitation of the myosin by dilution with water. 



Myosin may be most readily extracted from muscle by means of 

 ammonium chloride solution, and may be precipitated in a gelatinous 

 form by dialysing away the salt. 1 Elementary analysis 2 gives the 

 following results : -C, 5279; H, 712; N, 16'86 ; S, 1-26; 0, 22*97. 



Eecent research has shown that calcium salts are essential for the 

 effective coagulation of milk and blood. The facts are not so positive 

 in the case of muscle, but there is some evidence pointing to the 

 existence of an analogy in the three cases. 3 



By fractional heat coagulation, and by their varying solubilities in 

 different salts, I was able to separate four different proteids iii the 

 muscle plasma. 



(1) A globulin precipitable by heat at 47 C. This is analogous to 

 the cell globulin found in most protoplasmic structures. It is termed 

 musculin by Hammarsten. I gave it the name paramyosinogen. 



(2) A globulin precipitated by heat at 56 C. This is the proteid 

 which is especially acted on by the myosin ferment, and is converted 

 into myosin. I termed it myosinogen: both it and paramyosinogen 

 contribute to the muscle clot. 



(3) A third globulin precipitated at 63 C. (myoglobulin) is con- 

 tained in the muscle serum. 



(4) Small quantities of an albumin (myoalbumiri), similar in its 

 properties to serum albumin, are also present. 



In addition to this, in the case of red muscles, there is haemoglobin ; 

 and if the muscle has been kept warm, and acidity developed, small 

 quantities of proteoses and peptone, which are formed by a process of 

 self-digestion. Briicke showed, many years ago, that muscle contains 

 small quantities of pepsin, doubtless absorbed from the gastric mucous 

 membrane ; this becomes active on the onset of acidity. The action of 

 such a ferment within the body will perhaps explain the phenomenon 

 called the disappearance of rigor mortis'., it is unnecessary to suppose 

 that this is always due to putrefactive organisms, 4 since rigor often dis- 

 appears before putrefaction sets in. Perfectly fresh muscle contains no 

 proteose or peptone. 5 



Whitfield also investigated the question whether myosin or its precursors are 



1 Kiihne and Chittenderi, Ztschr. f. Biol., Miinchen, Bd. xxv. S. 358. 



2 Chittenden, ibid. See also Stud. Lab. Plujsiol. Chem., New Haven, 1889, vol. iii. 

 p. 116. 



3 Locke, Journ. Physiol., Cambridge and London, vol. xvii. p. 293 ; other references will 

 be found in this paper. 



4 Cossar Ewart, Proc. Physiol. Soc., London, 1887, p. xxv. 



5 Whitfield, Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 487. 



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