1887.] 



and its Relation to Putrefaction. 



451 



■5° 0., but at temperatures below 5° 0. the difference is less evident, 

 the cold serving either to paralyse the nervous system or to prevent 

 the muscles responding to the weak stimulations which reach them. 



If two fish, one (A) with brain and cord destroyed, the other (B) 

 with both intact (B having been allowed to die slowly in the net), are 

 placed in water at a temperature of 25° C, the rigor in (A) persists 

 for 2J- to 3 hours, while in (B) it vanishes in \\ to 2 hours. If two 

 similar fish are kept under observation at a temperature of 5° C, in 

 the pithed specimen the rigor may last three days, while in the other 

 it may not last 48 hours. As it is impossible to suppose any vital 

 •changes take place after the rigor appears, its duration must depend 

 on the condition the muscles are in when they become rigid, so that 

 we must account for rigor in pithed fish persisting longer than in fish 

 .allowed to die naturally, in the same way as we account for rigor 

 setting in at different times in fish differently treated. 



There is little to add to what has been already said as to the 

 influence of temperature in driving off or maintaining rigor. In 

 runpithed fish the rigor at a temperature of 35° G. may only last 30 

 minutes, at 25° C. it may last 5 hours ; at 15° C. it may persist for 

 24 hours ; at 10° C. 36 hours ; at 5° C. 46 hours ; at 1° C. three 

 days. At — 2° C. it continues unchanged for an indefinite time. On 

 the other hand, in fish which after the rigor had set in were kept for 

 .several days at a temperature between — 7° C. and — 20° 0., the rigor 

 -disappeared before the thawing was completed. 



Perhaps the rigor was destroyed by alterations produced in the 

 muscular fibres during freezing. It was certainly not owing to the 

 direct contact of the salt and ice freezing mixture, for the same 

 results were obtained when fish were frozen in air, and in fresh water 

 in stoppered bottles. That the rigor persists until the fish are thawed 

 does not seem probable, because it persists for some time after thawing 

 in fish which have been for ten days at — 2° C, and true rigor never 

 appears in fish which have been kept for several days below — 7° C. 



The duration of rigor which occurs after death from an electric 

 shock varies considerably, the variation evidently depending either 

 on the direct influence the charge has had on the muscles or on the 

 condition of the central nervous system after the shock. In a trout 

 which was killed and thrown into instantaneous cataleptic rigor 

 -at one and the same moment, the rigor began to disappear from 

 the jaw and gill- covers 1\ hours afterwards, and 16 hours later 

 it had completely passed off. In another trout in which only 

 the anterior half was stimulated, the rigor had passed off 9 hours 

 afterwards, about 3 hours after the rigor appeared in the pos- 

 terior unstimulated portion. Conversely when the shock was 

 passed through the posterior half of a trout, the rigor continued 

 until 8J hours after death, while the rigor in the anterior half, 



