454 Dr. J. C. Ewart. On Rigor Mortis in Fish, [June 16, 



tain what ground there was for entertaining this notion, I proceeded 

 to study the origin and nature of rigor in fish and other animals. 

 At a very early stage I learned that the longer the rigor lasted the 

 longer putrefaction was delayed, and also that putrefaction set in 

 quicker in fish in which there was a large amount of putrescible 

 matter in the alimentary canal, than in fish in which the alimentary 

 canal was practically empty. For studying the relation of bacteria to 

 the disappearance of rigor, I at the outset used sea fish, but afterwards 

 trusted chiefly to fresh water forms, owing to the great difficulty 

 in obtaining haddock and other fish in a perfectly vigorous condition. 

 I soon observed that haddocks and whiting which were knocked on 

 the head when captured (after the manner long practised by the 

 fishermen who send "live" cod to Billingsgate) were longer in 

 stiffening than fish which were left wriggling as long as their energy 

 lasted in the hold of the boat. Later I found that the rigor per- 

 sisted longer in haddocks and whiting which were gutted immediately 

 after capture than in ungutted fish. If, e.g., we take six haddocks 

 (about the same size and captured on the same fishing bank at or 

 about the same time) and, (1) leave two (Series A) to die in the 

 usual way (temperature 7 — 8° C, (2) kill two (Series B) by 

 knocking on the head and then pith, and (3) kill the other two 

 (Series C) and both pith and gut; in Series A the rigor may 

 appear 10 minutes after death, bat in B and C it may not set 

 in for 2 or 3 hours. Further, in A the rigor may have disappeared 

 from the trunk (the portion co- extensive with the body- cavity) 

 10 hours after death, while in B it may persist for 13 hours, and 

 in C for 20 hours, and while A might be quite limp 21 hours after 

 death, B might continue rigid for 25 hours and C for 30 hours after 

 death. 



It may be taken for granted that rigor results chiefly from the 

 formation and coagulation of myosin, and further, that the intensity 

 of rigor depends on the amount of myosin formed in the various 

 muscles. If nearly all the myosin-forming material has been used 

 up before rigor appears in producing muscular contractions, compara- 

 tively little myosin will be formed, while in fish which have been 

 pithed (if pithing diminishes the muscular contractions) there will be 

 (except when the rigor is greatly delayed, as in the tail of the eel) 

 sufficient material left to admit of a considerable amount of myosin 

 appearing in the substance of the muscles. 



But after all the amount of myosin formed in any given muscle 

 accounts rather for the firmness of the muscle during the rigor than 

 for the duration of the rigidity. Why does the myosin not continue 

 unchanged ? Why does it not, as it were, liquefy ? And why does the 

 rigor persist not only longer in some fish than in others, but also 

 longer in some parts of individual fish than in others ? 



