226 BACTERIA, YEASTS, AND MOLDS 



ably due to the development of toxic substances in some 

 food products, since almost any of the putrescible foods 

 which come upon our tables may, in warm weather and 

 under certain circumstances, undergo a type of putrefac- 

 tion which gives rise to these poisons. When this occurs, 

 "ptomaine poisoning" is quite likely to follow the use of 

 the foods. It is probable that a large part of the summer 

 diarrhcea so common in warm weather is due to poisonous 

 decomposition products developed in some of our foods. 



Unfortunately we know very little concerning the con- 

 ditions under which such poisonous materials appear. Not 

 all bacteria produce them, and it is only rarely that food is 

 thus rendered unwholesome by bacteria. We know that 

 strictly fresh foods never contain these poisons. We know 

 that their development is dependent in a measure upon 

 temperature, inasmuch as they do not develop in food that 

 is kept sufficiently cold. We know that decomposition 

 products are more likely to give rise to toxic substances in 

 the absence of oxygen than in its presence. We know, lastly, 

 that injurious substances are produced by bacteria ; but we 

 do not yet know the source of the bacteria, nor have we, 

 for this reason, discovered any methods for keeping them 

 from our foods other than those ordinarily adopted for 

 checking bacterial growth. Anything that will prevent 

 bacteria from growing will prevent "ptomaine poisoning." 

 Consequently low temperature, dr)dng of foods, and the 

 other devices already suggested are the only means we have 

 for guarding ourselves from such troubles. We may well 

 remember that such poisoning is most likely to occur in 

 foods that have been kept for some time in a moderately 

 warm temperature. 



