of the Fishery Board for Scotland. 2 5 



11. Detection of Rigor Mortis. 



When rigor is strongly and fully developed its presence is easily 

 detected. The fish is quite rigid or nearly so according to the degree of 

 rigor, which again depends on conditions already discussed. When one 

 balances such a fish on the finger it may remain quite rigid, but when 

 rigor is beginning to pass off it may begin to droop at head or tail 

 or both. Here it is often difficult to be certain about the condition, 

 and especially when rigor has not been well developed. But when rigor 

 is passing away one will observe that the fish, from being firm and elastic 

 to the touch, becomes softer and inelastic and pits readily on pressure. 

 The chemical changes are always fairly definite during these transitions. 

 Preceding rigor, while the muscles are irritable and respond to stimuli, 

 their reaction is neutral or faintly alkaline. During rigor they are 

 strongly acid. As rigor passes off they become neutral. Then as 

 decomposition ensues they become strongly alkaline when tested with 

 litmus paper. 



This part of the subject has been discussed in considerable detail, and 

 the reasons for this must be stated. We have found, on the one hand, 

 that those who have to do with the preservation of fish in the fresh state 

 have not given the subject due consideration, nor recognised the great 

 commercial value, and yet it is the initial and most important stage in 

 the process of fish preservation ; and we have found, on the other hand, 

 that this subject is often inadequately understood by those whose duties 

 are to examine fish in the interests of public health. They likewise 

 fail to take advantage of an invaluable criterion, which, when present, 

 stamps fish as absolutely fresh, or, if absent, points to ensuing putre- 

 faction and decomposition. 



, 12, Trawl Fish compared with Line Fish. 



Since the advent of the great trawling industry the question has often 

 been discussed as regards the general condition, curing properties, and 

 keeping properties of trawl fish as against line-caught fish. But, at the 

 present time, opinion is very much divided. 



Professor Macintosh, in an Appendix to the Report of the Trawling 

 Commission, 1885, states that the general condition of trawl fish is 

 excellent and that they become rigid like line-caught fish, whereas, on 

 the other hand, it is the experience of many fishcurers that it is often 

 difficult to cure such fish, especially as findon haddocks. 



I have examined many lots of fish taken from the trawl net after being 

 a certain number of hours at work and treated under different conditions. 

 Some were killed when taken out on board, some not killed, some gutted, 

 and some ungutted. When such fish are compared with line fish under 

 similar conditions, it will be found generally that rigor sets in earlier and 

 disappears earlier in the trawl fish. 



The reason for this is evident when one considers the conditions under 

 which fish are trawled. The longer the fish remain in the trawl net the 

 more do they become crowded together, while the motion of the net 

 through the water maintains a certain degree of compression. Respira- 

 tion is consequently impeded while the fish are struggling to respire and to 

 get freedom. Trawled fish are also subjected to considerable pressure 

 while the net is being brought on board. The result is that the tissues 

 are not sufficiently oxygenated, waste products accumulate, and the fish 

 become more and more exhausted the longer they remain in the trawl net. 

 Fishcurers frequently observe this condition in herrings which have been 



