386 CHEMISTRY OF THE PROTEIDS (HAP. 



(1) at 47-50, (2) at about 63 ; and also a tendency to contract at 

 about 56. The first of these, we conclude, is due to the coagulation 

 by heat of the proteid substance present in the muscle-fibre during 

 life (' paramyosinogen '), the second to changes in the connective-tissue 

 elements of the muscle; 1 the slight change at 56 we attribute to the 

 presence of small quantities of ( myosinogen,' this slight change being 

 the more marked, but never larger, in muscle in partial rigor." 



"Amphibian muscle shows marked differences from the above when 

 submitted to heat rigor experiments. The striped muscle of these 

 animals gives a contraction at 38-40, due to coagulation of soluble 

 myogen-fibrin, and another at 45-50. The unstriped muscle gives 

 only a marked contraction at 54, sometimes a slight one at 47. The 

 former contraction, we think, is due to the connective tissue." 



Kiihne's soluble myosin Halliburton believes to be the mother-sub- 

 stance of myosin and calls it myosinogen. This change is expressed 

 diagrammatically by Halliburton 2 thus : 



Muscle-plasma 



/\ 



I ! 



Paramyosinogen Myosinogen 



(myosin of v. Fiirth) (myogen of v. Fiirth) 



Soluble Myosin 

 (Soluble myogen-fibrin 

 Myosin-fibrin of v. Fiirth) 



Myosin or muscle-clot. 



There is thus a complete analogy between fibrinogen- and myosinogen- 

 coagulation. v. Fiirth agrees with Halliburton in assuming two 

 coagulable substances to exist, namely, the myosin and the myogen. 

 Przibram 3 and Steyrer 4 have also adopted Halliburton's view in all 

 essential points. 



Przibram has studied the distribution of paramyosinogen and 

 myosinogen amongst different classes of animals, and has arrived at 

 results which Halliburton has summarised as follows : 



Invertebrates : paramyosinogen present ; myosinogen absent. 



Vertebrates : paramyosinogen and myosinogen both present. 



1 Brodie and Richardson. See footnote, p. 385. 



2 Halliburton, Handbook of Physiology, 1904, p. 156; and Biochemistry of Muscle 

 and Nerve, 1904, p. 10. Murray, London. 



3 H. Przibram, Hofmeister's Beitrage, 2. 143 (1902). 



4 A. Steyrer, ibid. 4. 234 (1902). 



