112 INLAND FISHERIES. 



and are then shipped in specially constructed steamers. This 

 freezing of the fish does not immediately kill the bacteria present, 

 but prevents their reproduction for the time being, Koch has 

 found very many bacteria in fish that have been treated in this 

 way. Foster has found that certain germs increase in meat stored 

 at moderately low temperatures, though actual putrefaction is not 

 produced by them. Moreover, the researches of Frajnkel, Bordoin, 

 UjBfreduzzi, Prudden, and Heyroth show us that natural ice may 

 contain both putrefactive and pathogenic bacteria. This fact 

 alone should teach us to look with suspicion upon any meat that 

 has been brought in direct contact with ice, especially where the 

 ice is allowed to melt and the drip to permeate the flesh. 



It is worthy of note in this connection that poisonous ptomaines 

 do not begin to appear until about the seventh day of putrefac- 

 tion, and that they finally disappear, if putrefaction is allowed 

 to go on for a considerable time. The toxicity of the ptomaines 

 themselves is not afi"ected by cooking, no matter how thorough 

 this may be. There are two distinct kinds of poisoning that may 

 arise from the use of fish as food. The first is an intoxication 

 caused by the devouring of meat Avhich has become invaded 

 by ptomain-producing bacteria. The second is an intoxication 

 brought about by fish not necessarily infected with bacteria, but 

 in which the poisons are leucomames produced by the tissues of 

 the fish and their normal product, in the same way that certain 

 toad-stools are always poisonous. 



