BACTERIA IN FOODS 233 



or three weeks, the typhoid bacillus retaining its character- 

 istics unimpaired, the cholera bacillus tending to lose them. 



3. Oysters from sources free of sewage contained no 

 bacteria of sewage, 



4. Oysters from sources exposed to risk of sewage con- 

 tamination did contain colon bacilli and other sewage 

 bacteria. 



5. In one case Eberth's typhoid bacillus was found in the 

 mingled body and liquor of the oyster. 



Nor do typhoid bacilli lose activity or virulence by passing 

 through an oyster. 



These researches once and for all established the fact that 

 oysters ordinarily grown on oyster-beds contaminated with 

 bacteria may, and do on occasion, contain the virulent 

 specific bacillus of typhoid, which can live both in sea-water 

 and within the shell of the oyster. This being so, it will 

 probably appear to the reader that the risk of infection of 

 typhoid by oysters is very serious indeed. Yet in actual 

 practice many conditions have to be fulfilled. For, in ad- 

 dition to the fact that the oysters must be consumed, as 

 is usual, uncooked, the following conditions must also be 

 present ; 



{a) Each infective oyster must contain infected sewage, 

 which presupposes that typhoid excreta from patients suffer- 

 ing from the disease have passed into that particular sewage 

 untreated and not disinfected. 



(U) The infective oyster must be fed upon infected sew- 

 age, and still contain the virus in its substance. 



{c) It has to be eaten by a susceptible person. 



(d) There must have been no period of natural cleansing 

 after " fattening.*' 



Even to this formidable list of conditions we must add the 

 further remark that, owing to the vitality of the body-cells 

 of the oyster, or to the lessened vitality of the bacilli of 

 cholera and typhoid, it is generally the case that the tend- 



