28 



Part III. — Twenty-sixth Annual Report 



From a large number of observations I came to the conclusion that the 

 kind of food in the stomach exercises some, but not an important, 

 influence on the time when decomposition sets in and the rate of its 

 progress. In the fish fed on carbo-hydrates, digestion of the wall of the 

 gut, when it did take place, was slower than in those fed on proteid 

 foods, and on the average decomposition was slower in appearing. Still, 

 it has to be kept in view that very few edible fish in their natural habitat 

 feed on carbo-hydrates, so that this observation does not possess much 

 practical value. 



Far more important, however, as regards the onset of decomposition, is 

 the time after feeding when the fish are killed. Invariably, in those 

 killed from 15 to 45 minutes after feeding, post-mortem digestion 

 appeared to be more active. Consequently, in a greater number of these, 

 digestion and solution of gut wall took place sooner than in those killed 

 at a later period of from one to two hours after feeding. This obser- 

 vation is in accordance with Pawlow's experimental work on gastric 

 secretion and digestion — that increase in quantity of food, and especially 

 proteid food, causes a more active secretion of gastric juice, and that the 

 secretion is more abundant in the earlier stage of digestion, or soon after 

 the ingestion of food. 



This part of the enquiry, however, must be studied in a wider and 

 more natural field than within the confines of the laboratory. Here the 

 environment is so different to that which obtains in nature, and to which 

 fish do not become readily acclimatised. I have often discussed this 

 question with intelligent and observant fisher people, who assure me that 

 the keeping, curing, and edible qualities of fish vary greatly with the 

 nature of the ground on which they have been living and feeding. So 

 much so is this the case that they associate soft ground with soft fish and 

 hard ground with hard fish, and map out large areas of fishing ground 

 accordingly. They are of opinion that the foodstuff obtained on the 

 soft ground consists chiefly of worms and small fish, while that obtained 

 on the hard ground consists largely of Crustacea, and this to a certain 

 extent agrees with my own observations. This statement is also in 

 agreement with the experience of many fishcurers, who tell us that soft 

 fish do not keep so long fresh and are more difficult to* cure. 



Then there are what is known as " spawny haddocks." These have 

 been feeding for some time on herring spawn at certain seasons of the 

 year. Now, fishermen and curers inform me that such fish are very 

 difficult to keep fresh, and show early signs of decomposition. Hence it 

 is possible that the food of fishes differs in kind and quality in different 

 parts of the sea and at different seasons of the year in such a way that it 

 has some influence in determining not only the earlier or slower onset of 

 decomposition, but also the quality of the flesh of the fish and its curing 

 and edible properties. 



As one would expect, temperature plays a very important part in all 

 processes of putrefaction and decomposition in fish. At freezing point, 

 it is supposed, these processes are, if not destroyed, at least inhibited. 

 But I find that fish ungutted and packed in ice, when removed from the 

 iced condition, always begin to exhibit commencing signs of decom- 

 position earlier than fish which have been gutted immediately on capture 

 and then packed in ice. Hence it is quite possible that the degree of 

 cold produced by icing fish, as it is generally carried out on board 

 trawlers, may not altogether inhibit fermentative changes taking place in 

 the gut. 



From these observations I conclude that the chief factors concerned in 

 determining the rapidity of post-mortem digestion and solution of the 



