PEESERVATION OF FISH BY SALT. 19 



Every species of bacteria is acclimated to some particular set of 

 conditions, some of them almost incredible for living things. These 

 red bacteria are accustomed to live and grow either on moist salt or 

 very strong salt solutions. If bacteria are particularly resistant to 

 some condition, as to strong salt in this case, it does not follow that 

 they are likewise resistant to all severe conditions. It is the bac- 

 teriologist's business, by studying all the habits and peculiarities of 

 the organism, to discover its weakest point where attack will destroy 

 it. The strongest resistance of these bacteria, that against salt, is 

 also the weakest, for it has been found that water less than 15 per 

 cent saturated destroys them. Thus, the present indications are that 

 the best and simplest remedy for the trouble is clean, fresh water 

 and i^lenty of it. There is some evidence that may support the view 

 that the usual impurities in salt, calcium and magnesium compounds, 

 are essential to the growth and multiplication of these bacteria. 

 The implication here is, of course, that pure salt itself would be a 

 poor supporter of the bacteria. Of course, it would be futile to try 

 to stop the reddening of cod as long as every shipment of salt brings 

 new infection, and the butts, floors, buildings, and the surroundings 

 at packing plants are heavily infected. Facts already given indi- 

 cate also that for other reasons salt free from impurity is better. 

 The results of the study of reddened cod only emphasize this advice. 



The research on reddening should not, however, end here. We are 

 again dealing with questions of permeability. The bacteria are ad- 

 justed to strong salt solutions, that is, the body fluid is of such con- 

 centration and their covering membrane is of such partial perme- 

 ability that when surrounded by strong salt solution they live nor- 

 mally, but when water or weak brine surrounds them these relations 

 are disturbed and they die. Probably water enters the cell in ex- 

 cessive quantity. It is known that the reddening does not attack 

 fat fish. Perhaps the fat acts directly on the membrane, or indi- 

 rectly by acting on the calcium and magnesium in the salt, to effect 

 the disturbance. 



RECOVERY OF BRINE. 



Even crude salt now costs considerably more than coal. Yet the 

 fish packers, who are usually very careful to economize in coal, are 

 prodigal in the use of salt. Every hundred pounds of brine that 

 goes overboard contain about 25 pounds of salt, to say nothing of the 

 valuable nitrogenous matter that the brine has extracted from the 

 fish. Considerable work has been done by the writer and his as- 

 sociates on the development of a process to reccver salt and other 

 substances of value from old pickle by precipitating the proteinace- 

 ous matter with sodium silicate. A trial plant was in use and under 

 observation at an important fish-pacldng establishment for over a 

 year but was not satisfactory under the circumstances. Brine pure 

 enough for use was recovered, while a substance very rich in 

 nitrogen was yielded as a by-product. This substance in the dry 

 condition is nearly white and friable and contains enough nitrogen 

 to command a handsome price as fertilizer if suitable for that pur- 

 pose, but it may be more valuable for other uses. The method re- 

 covered brine, and for this reason some other method that would pro- 



