1887.] 



and its Belation to Putrefaction. 



443 



possible the same size, which have been living under as nearly as 

 possible identical conditions since the day of hatching, are captured 

 at the same moment while lying quietly in the corner of a tank, and 

 allowed to die in the landing net, the rigor may appear in one (A) 

 15 minutes after death, in another (B) 30 minutes, and in the third 

 (C) 40 minutes after death. We must suppose that this variation 

 results either from the condition of the muscles at death, or from the 

 influence of the nervous system. 



If at death the muscles of (C) contained (owing to the oxygenation 

 of the blood continuing longer) less bye-products than (A), it might 

 be possible to understand why the time at which the rigor set in 

 differed. Again, if in (A) the nervous system continued to produce 

 muscular contractions longer than in (C), i.e., led to the more com- 

 plete exhaustion of the muscles of (A) than (C), the difference might 

 be easily understood. It is of course difficult, if not impossible, to 

 determine which (if either) of these explanations is the correct one, 

 but that they may both have some influence in the result may be in- 

 ferred from the following facts. (1.) If two trout are taken from the 

 water at the same time, and one is left with its gills freely open in 

 the landing net, while in the other the gills are kept firmly closed by 

 an elastic band, the one with the gill-covers extended will die, it may 

 be 20 minutes before the other,* but will be 30 to 40 minutes later in 

 becoming rigid, the reason apparently being that the closed gill-covers 

 prevent the evaporation from the gill-chamber, and the consequent 

 increase in temperature and loss of function of the gill-filaments. 

 ("2.) If two trout are taken from the water at the same time, the one 

 allowed to die in the landing net, while the other is at once killed and 

 pithed, the rigor sets in in the former several hours (4 — 8) sooner 

 than in the latter, i.e., it is later in appearing in the fish in which the 

 brain has been destroyed. 



Although in some cases it is difficult to account for the time at 

 which the rigor sets in, fairly satisfactory explanations can be given 

 in others. It is well known that most fish can live for months with- 

 out food. In fact fish in confinement often appear to " thrive " best 

 when not fed, they are less sensitive and less liable to suffer from 

 disease. Even in a wild state fish seem to all but give up feeding for 

 weeks at a time, more especially during the spawning season, and the 

 chief difference between under-fed and well-fed fish appears to be that 

 in the former there is little or no growth, and the spawning period is 

 delayed or the formation and maturation of the roe and milt are 

 arrested. But although many fish are capable of living for months 

 without food in aquaria, now and then one sickens and dies without 

 any apparent cause. 



* This was first pointed out to me by Sir James Maitland, Bart., -when visiting 

 the Howieton Fishery. 



