of the Fishery Board for Scotland. 



23 



On the other hand, rigor appears earlier and disappears sooner in the 

 following conditions : — 



A 1 . Fish not in season. 



B 1 . Fish in an exhausted condition. 



C 1 . Fish not killed at time of capture. 



D 1 . Fish neither killed nor pithed at time of capture. 



E 1 . Fish ungutted. 



F 1 . Fish roughly handled. 



G 1 . Fish not iced and not kept at low temperature. 



It is also to be observed that rigor tends to persist longer in those 

 varieties of fish, such as salmon, whose muscular tissue is firmer in 

 texture and contain a smaller percentage of water than in most varieties 

 of white fish, such as whitings and haddocks, where the tissues are not so 

 firm and contain more water. 



From these observations we must conclude that the degree and duration 

 of rigor in fish depends chiefly on the condition of the muscular tissues 

 at time of death. The more the conditions at time of death approximate 

 A, B, C, D, E, F, G the later will rigor set in — sometimes not for 10-30 

 hours — and it may persist 1-3 days, whereas the more exhausted the 

 fish is, when conditions A 1 , B 1 , C 1 , D 1 , E 1 , F 1 , G 1 obtain, the sooner 

 rigor appears and disappears. Sometimes it is even difficult to detect. 



The cause of the disappearance of rigor in muscle is a question regard- 

 ing which all are not agreed. True it is that, in muscle in condition of 

 rigor, the conditions for pepsin-digestion are present. The muscle is acid, 

 and pepsin ferment, although in a very small quantity, is also present. 

 Still it appears that although pepsin-digestion may play some part in the 

 initial stage, it is a small one, and that the chief and final cause is due to 

 bacterial invasion. It is very rare to find any micro-organisms in muscle 

 during rigor, but as rigor passes off they increase rapidly. 



As already stated, to preserve fish as long as possible in rigor, condi- 

 tions A, B, C, D, E, F, G have to be observed, and. in practice the most 

 important is G — the maintenance of low temperature. 



Since it is possible to inhibit the action of most bacteria of putre- 

 faction by maintaining a low temperature from 0°C. to -3°C, while at the 

 same time maintaining the fish in a condition of rigor, it thus becomes 

 possible to preserve fish in a comparatively fresh condition for a con- 

 aiderable time with very little deterioration in their tissues. At 

 temperatures below -3° C. the fish suffer considerably. When such fish 

 are thawed they are usually found to be very soft and limp, and pit 

 deeply on pressure. The lower the temperature the deeper and more 

 extensive the freezing of the water in the tissues, which must cause at the 

 same time a proportionately greater amount of mechanical disintegration. 

 Such fish are more difficult to cure ; when cooked they are found to have 

 lost much of their natural flavour, and they very readily undergo decom- 

 position. By maintaining the temperature about -4° C. to 5° C. fish 

 appear to remain in a condition of rigor indefinitely. If the temperature 

 is kept at -5° C, or lower, fish do not appear to pass into rigor, but may 

 be observed to do so on raising the temperature above -4° C. 



It has so happened that on some occasions the fish I was experimenting 

 with were kept in a mixture of sawdust and ice. This combination 

 impressed me favourably, and it appears to be more effective in maintain- 

 ing rigor and inhibiting the onset of decomposition than ice alone The 

 best mixture appears to consist of small lumps of ice, with the interven- 

 ing spaces filled up with sawdust. Although I have not been able as 



