PRESERVATION OF FISH BY SALT. 21 



to insert a needle in the gill arch and with pressure completely irri- 

 gate the whole system of arteries and veins of a fish, removing abso- 

 lutely all the blood at one stroke without cutting the fish. 



CONCLUSIONS. 



The preservation of fish by means of salt is an excellent method, 

 even in the crude and inexact manner in which the art has hitherto 

 been practiced. The comparatively small amount of scientific re- 

 search that has been done on the problems and principles involved 

 has not only justified itself in practice but furnishes abundant 

 grounds for the expectation that a great deal more of valuable results 

 will follow further work. It is not mere guessing to say that when 

 advantage is taken of all that is known of improved salting methods 

 a fish nearly if not quite equal in edible qualities to fresh fish is ob- 

 tained, and in some cases the quality is decidedly improved by salting. 



There is every reason to expect a good future for the salt fish in- 

 dustr}^, but progress must be made. Preservation by this method is 

 eminently practicable, simple, and reliable for holding and transport- 

 ing our sea fislies to the inland population. 



SUMMARY. 



1. A discussion of the principles involved in the preservation of 

 fish by salt has been presented. 



2. Salt possesses no inherently peculiar preserving qualities, but 

 preserves food by extracting water. 



3. The principle by which salt (and other soluble substances) in 

 concentrated solution extracts water is called osmosis. Osmosis is 

 the passage or interchange of liquids and solutions through mem- 

 branes which are more or less permeable. The permeability of cell 

 membranes in fishes appears to be affected by high and low tem- 

 peratures. The presence in or absence from the salt of certain im- 

 purities, notably calcium and magnesium compounds, the treatment 

 of the fish, and the staleness of the fish, are factors which govern the 

 permeability and have an important bearing on the preservation of 

 fish by salt. 



4. Calcium and magnesium compounds in addition to retarding 

 penetration cause a whitening and hardening of the fish. There are 

 chemical reasons for looking upon this whitening and hardening by 

 these compounds as undesirable. 



5. The flavor of fish is often altered by the salting process. Cal- 

 cium salts retained in the tissue increase the salty taste and make 

 necessary a prolonged soaking out. Undesirable flavors of fishes 

 from muddy waters may sometimes be removed by salting the fish. 



6. Salt applied dry penetrates the fish more rapidly and effects a 

 quicker cure with less danger of spoilage in warm weather. 



7. There is a very material loss of protein material from fish 

 during the salting process. This material probably arises from the 

 decomposition products ordinarily unable to pass out of the cells but 

 which are digested by autolysis, an internal destructive process. 



8. Autolysis is increased by crushing, bruising, rough handling, 

 pewing, elevated temperatures, low temperatures followed by a rise, 

 and, in general by factors that increase cell permeability. It is 



