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



from the apparently exhausted electric organs, began to stiffen 10 

 hours afterwards, and were quite rigid \1\ hours afterwards, the 

 temperature varying from 50 — 44° F. On the 3rd April two other 

 roach were l ' struck " when the fish was vigorous, one was killed by 

 the first shock, the other after receiving two shocks, and both were 

 quite rigid hours afterwards. We thus see that the setting in of 

 the rigor is related to the strength of the shock received, but that 

 even when the shock is strong enough to cause instantaneous death 

 the rigor is delayed for several hours. The advantages of being able 

 to kill the fish instantaneously without producing immediate rigor is 

 evident enough. It would be often uncomfortable if not impossible 

 for Gymnotus (and still more for the small-mouthed torpedo) to 

 swallow a fish in strong rigor, and yet unless the fish were sufficiently 

 "numbed " they would readily escape from their sluggish destroyers. 

 It may be mentioned that a trout which had been pithed immediately 

 after death and placed in artificial gastric juice at a temperature of 

 100° F., became rigid in less than a minute, and the rigor com- 

 pletely disappeared 35 minutes later. A similar fish in water at the 

 same temperature became at once rigid, but the rigidity persisted 

 for an hour and ten minutes. 



Experiments were made to determine the influence of acid, alkaline, 

 and other solutions in bringing on and keeping back rigor. Salt 

 solution, as is well known, prevents rigor setting in in proportion to 

 its coming into contact with the muscles. Alkaline and septic solu- 

 tions seem to have no influence either way, while acid and corrosive 

 solutions seem to hasten its appearance, but the latter only to a limited 

 extent. Generally speaking, whatever tended to influence the rigor 

 influenced the irritability of the muscles, but at low temperatures 

 there was no relation between the disappearance of the irritability 

 and the setting in of the rigor. The muscles lost beyond recovery 

 their irritability in the trout when the temperature was kept for a 

 few minutes at —70° C, but while this temperature was maintained 

 no rigor appeared, and, as mentioned above, fish which were kept 

 under —70° C. for several days never became rigid when removed 

 from the freezing mixture ; in some cases, however, they seemed to 

 become slightly firmer — the continued freezing probably so alters the 

 tissues that the usual coagulation or stiffening is rendered impossible. 



4. The Duration of Rigor, 



There is, as generally believed under ordinary circumstances, a 

 close relation between the duration of a rigor and the time at which 

 it sets in ; i.e., if a rigor sets in half an hour after death, it is not likely 

 to Jast long, while if it appears twelve hours after death, there is a 

 probability that it will continue for several hours. On the other hand, 



