136 American Fisheries Society 



ing fish, require a certain amount of new protein to support 

 body activities which failing, the animal would immediately 

 perish. But the hazards in the existence of any animal often 

 make it obligatory to do without food for a shorter or longer 

 period. If the stomach became empty because of temporary 

 shortage of food or an injured mouth, the animal would die 

 unless special provision were made to supply protein from some 

 other source. But nature has kindly provided a means whereby 

 the proteins in the less important parts of the body can be 

 used, for the time being, to support the activities of the abso- 

 lutely necessary vital parts. The stored protein is within cells, 

 and could not possibly be carried by the blood stream to the 

 point of need unless it could get out. So there is in each cell 

 stored along with the protein some enzyme ready in case of 

 threatened starvation to break the protein down into simpler 

 substances which penetrate outward into the blood for trans- 

 portation to the point of need. The writer, in certain experi- 

 mental work, kept some pigfish (Orthopristis chrysopterus) for 

 three months absolutely without food. They lived at the 

 expense of their own bodies, the proteins apparently being 

 digested by autolytic enzymes. 



These enzymes, present in every part of the fish, while 

 almost an absolute necessity to the living fish, become the 

 greatest enemy of the dead fish, for they soften and liquefy 

 the cell contents, cause unpleasant tastes and odors, and permit 

 the contents to escape from the cell into brine. The proteins 

 could not escape as long as they were proteins, but when they 

 are broken down by autolysis into simpler substances the latter 

 rapidly diffuse into the brine and are lost. This, at least, is 

 the hypothesis supported by some facts. 



What factors promote autolysis, and what factors oppose it? 

 Warm temperatures promote it directly. A temperature suf- 

 ficiently high to destroy the enzyme stops it. Low temperatures 

 retard it directly. 



If cells are ruptured as they often are by rough handling of 

 the fish, autolysis rapidly decomposes the protein ; and for this 



