CHEMICAL CHANGES IN MUSCLE 



protein, giving rise to a precipitate in dilute 

 strong solutions. The properties of these pro 



ofetfe S to,e called soluble myogen TM S i a t, ST 7 "" intemedia " 



Muscle-plasma 



I 



myosin or paramyosinogen. * m y Oge n (myosinogen of Halliburton, 



albumate of Kiihne). 



| 

 Soluble myogen fibrin. 



Myosin fibrin. Insoluble myogen fibrin. 



' v^ ' ^ 



Muscle clot. 



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

 exists apparently preformed in frog's muscle. Hence the instantaneous clottii 

 frog's muscle-plasma on warming to 4C C. 



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

 chiefly of connective tissue, sarcolemma, 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-semm contains the greater part of the soluble constituents 

 of muscle. 



OTHER CONSTITUENTS OF MUSCLE. A number of other sub- 

 stances are found in muscle in small quantities, those which are soluble 

 being contained to a great part in the muscle serum. It will suffice here 

 to enumerate the chief of these. 



(a) Colouring-matter. All red muscles contain a considerable amount of haemo- 

 globin. A special muscle pigment allied to haemoglobin has been described by 

 MacMunn as myohsematin. The only evidence for its existence is spectroscopic. 



(6) Nitrogenous extractives. Of these, the most important is creatine (C 4 H 9 X 3 Oj) 

 of which 0-2 to 0-3 per cent, may be found in muscle. Its significance will be the 

 subject of consideration later. Other nitrogenous bodies occurring in smaller quantities 

 are hypoxanthine, xanthine, and traces of urea and amino-acids. 



(c) Non-nitrogenous constituents. 



Fats, in variable amount. 



Glycogen. This substance is invariably found in healthy muscle. Fresh skeletal 

 muscle contains about 1 per cent. In the embryo the muscles may contain many 

 times this quantity of glycogen. 



Glucose is present in fresh muscle in minimal quantities, about -01 per cent. 



When muscle is allowed to stand, especially in a warm place, the glycogen under- 

 goes partial conversion into glucose, so that the latter increases at the expense of the 

 former. 



