592 MICROBIOLOGY OF FOODS 



THE CHEMICAL NATURE OF FOOD POISONS 



The poisonous substances in foods are for the most part of the same 

 nature as the poisons of the pathogenic bacteria. The simplest in 

 structure of these poisons belong to the alkaloidal substances, substi- 

 tuted ammonia and ammonium compounds, called ptomains (page 241). 

 Several of these have been prepared in a pure state, for example, my tilo- 

 toxin (CeHisNC^) from poisonous shell-fish and neurin (C 2 H 3 -N- 

 (CH 3 ) 3 OH) from putrefied horse, beef, and human flesh. Although 

 ptomains undoubtedly occur at times in poisonous foods, they are not 

 now considered of so much importance in food poisoning -as formerly, 

 for in the majority of samples of poisonous food the search for ptomains 

 has been in vain. The poisonous effects are believed rather to be due 

 for the most part to much more complex bodies resulting from the 

 earliest analytic changes in the food protein, or else to bodies built up 

 by actual synthesis by the bacteria. Such substances are classed with 

 the toxic proteins and the true toxins. Their chemical composition 

 and structure are not definitely known. 



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