458 Dr. J. C. Ewart. On Rigor Mortis in Fish. [June 1 6, 



of the water. For some reason not easily understood, the fish preserved 

 in water at —1° C. were firmer and better in every way than fish at 

 the same temperature in boxes from which the water escaped as the 

 ice melted. Fish intended for drying and pickling, i.e., for preserving 

 for a long period, should also be treated before or as soon as possible 

 after the rigor goes. When a fish has once begun to disintegrate it 

 is impossible to restore the original freshness, and unless all the 

 flavours are destroyed during the preserving process the results of 

 previous decomposition can easily be detected. Some fish, as curers 

 well know, are incapable of being preserved even with salt, e.g., fish 

 which have died struggling in the water entangled in gill nets are 

 -difficult to preserve, because under these conditions, as experiments 

 prove (probably in consequence of the acid reaction thus determined), 

 no distinct rigor ever sets in — death being at once followed by putre- 

 factive changes. 



Fish hitherto have usually either been lightly salted and sun-dried, 

 or after being saturated with salt pickled in strong brine. A 20 per 

 cent, salt solution almost completely alters the tissues. Apparently salt 

 owes its preserving power to the fact that it arrests (though it fails 

 to destroy) putrefactive organisms by a process of desiccation — ex- 

 tracting the fluids, without which growth is impossible. 



Unfortunately we are acquainted with extremely few substances 

 able in small quantities to arrest the growth of bacteria without 

 rendering the fish unfit for food. It is extremely desirable to at least 

 greatly diminish the amount of salt required. This has recently been 

 rendered possible by a process introduced by Mr. Sahlstrom of the 

 Normal Company. In this process the fish are introduced into a 

 cylinder, and, after all the air has been removed by pumping, pressure 

 (5 to 6 atmospheres) is applied to drive the preservative solution 

 (which may contain salt alone, or salt along with other preserving 

 reagents) into the tissues. I have made an extensive series of ex- 

 periments by this method, and in all cases when fish in a rigid condition 

 were treated, succeeded in arresting putrefactive changes, either per- 

 manently or for a limited period according to the strength of the 

 solution used. 



This inquiry throws some light on another question which has long 

 been discussed, viz., whether line-caught fish are preferable to fish 

 taken by the beam trawl. In order finally to settle this question, it is 

 only necessary to ascertain whether the rigor disappears quicker in 

 the one case than in the other. I have already mentioned that a line- 

 caught haddock, which has been killed and pithed the moment it leaves 

 the water, may at a temperature of 8° C. remain stiff for 30 hours, i.e., 

 putrefaction may be retarded from 25 — 30 hours. On the other hand 

 haddocks, captured by a 25-feet beam trawl which had only been two 

 liours at work (large trawls are often down for six hours), even when 



