238 PHYSIOLOGY 



of which two, paramyosinogen and myosinogen, gave rise to the clot of 

 myosin. 



In no case, however, is it possible entirely to dissolve up the clot when once 

 formed, and it seems that the so-called solution in dilute salt solutions was 

 merely an extraction of still soluble protein in the meshes of the clot. Von 

 Fiirth has shown that if the muscles of a mammal are washed free of adherent 

 lymph and blood, the plasma obtained by extraction with normal salt solution 

 contains only two proteins. These proteins are extremely unstable, and are 

 gradually transformed on standing into insoluble protein, giving rise to a 

 precipitate in dilute solutions, or forming a jelly-like clot in strong solutions. 

 The properties of these proteins may be summarised as follows : 



(1) Myosin (paramyosinogen of Halliburton). A globulin, coagulating at 

 about 47-50 C., precipitated by half saturation with ammonium sulphate or 

 on dialysis. Transformed slowly in solution, rapidly on precipitation, into an 

 insoluble protein, myosin fibrin. 



(2) Myogen (myosinogen of Halliburton). A protein allied to the albumens 

 in that it is not precipitated by dialysis. Coagulates on heating at 55-60 C. 

 It changes slowly into an insoluble protein, myogen fibrin, but passes through 

 an intermediate soluble stage called soluble myogen fibrin. This latter . body 

 coagulates on heating to 40 C., being instantly converted at this temperature 

 into insoluble myogen fibrin. It does not seem that any ferment action is 

 associated with these changes, which we may represent by the following 

 schema : 



Muscle-plasma. 



j i 



| myosin or paramyosinogen. ^ myogen (myosinogen of Halliburton, 



albumate of Kiihne). 



I 

 Soluble myogen fibrin. 



Myosin fibrin. Insoluble myogen fibrin. 



Muscle clot. 



Soluble myogen fibrin, which in mammalian muscle-plasma forms only on 

 standing, exists apparently preformed in frog's muscle. Hence the instan- 

 taneous clotting of frog's muscle-plasma on warming to 40 C. 



The residue left after the expression of the muscle- plasma consists 

 chiefly of connective tissue, sarcolemrna, and nuclei, and as such 

 contains gelatin (or rather collagen), mucin, nuclein, and adherent 

 traces of the proteins of the muscle-plasma itself. 



The muscle-serum contains the greater part of the soluble con- 

 stituents of muscle. These are : 



(A) COLOURING-MATTERS. All red muscles contain a considerable 

 amount of haemoglobin. In many, a special pigment, probably allied 

 to haemoglobin, is also present. This has been named myohcematin 

 (MacMunn). 



(B) NITROGENOUS EXTRACTIVES. Of these, the most important 

 is creatin (C 4 H 9 N 3 2 -f- H 2 0), which occurs to the extent of 0-2 to 

 0-3 ner cent. This substance is found only in muscular and nervous 



