200 GENERAL BIOLOGY OF MICRO-ORGANISMS 



is chilled in cool water, then ice water, and finally stored in the 

 refrigerator. Immediately before feeding it is warmed by partial 

 immersion in warm water. 



Other Foods. — Other foods, meats, fish, eggs, vegetables 

 and fruits, undergo decompositions due to more or less definite 

 types of micro-organisms, and the activities of these are delayed 

 or prevented by modern methods of preserving foods, in some 

 instances very successfully, and in otlier cases with hmited 

 success.^ Any food, and especially that eaten without cooking, 

 may serve as a passive carrier of pathogenic micro-organisms. 

 Salads, green vegetables and fresh fruits may undoubtedly act in 

 this way during epidemics. Oysters taken from sewage-polluted 

 beds have been found to convey typhoid fever. Meats derived 

 from mammals may contain specific germs causing disease in 

 both animals and man, such as tuberculosis, anthrax and foot- 

 and-mouth disease. The flesh of bovine animals suffering with 

 enteritis at the time of slaughter seems to be particularly liable 

 to develop poisonous properties, and the ill effects observed in 

 these instances may have been due to a specific infection. Para- 

 typhoid fever is sometimes traced to such meat as a cause. 



Meats and fish are rich in protein and their decomposition 

 by saprophytic bacteria may give rise to various poisonous sub- 

 stances, as has been mentioned on page 177. The usual course 

 of putrefaction, however, goes on without very strong poisons 

 being produced^ as we may judge from the habitual use of partly 

 decomposed foods of this sort. Virulent poisons are occasionally 

 encountered and some of these are due to the presence of specific 

 microbes, B. hotulinus of Van Ermengen, B. enteritidis of Gaertner 

 and the paratyphoid and paracolon bacilli. 



' For a discussion of the microbiology of foods and .of food preservation see 

 Marshall's Microbiology for agricultural and domestic science students, 1920. 



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