OYSTERS AND TYPHOID 259 



the acid secretion of its digestive glands, or the water circulating 

 through its pallia] cavity, may act inimically on the germs. Proof 

 can be produced in favour of the third and last-named mode by which 

 an oyster can cleanse itself of germs. So far, then, we have met with 

 no facts which make it impossible for oysters to contain for a lengthened 

 period the specific bacteria of disease. Let us now turn to their oppor- 

 tunity for acquiring such disease germs. It is afforded them during 

 the process of what is termed " fattening." By this process the body 

 of the oyster acquires a plumpness and weight which enhances its 

 commercial value. This desired condition is obtained by growing the 

 oyster in " brackish " water, for thus it becomes filled out and medhani- 

 cally distended with water. But if this water contain germs of disease, 

 what better opportunity could such germs have for multiplication than 

 within the body-cavity of an oyster ? " The contamination of sea- 

 water, therefore, in the neighbourhood of oyster-beds may undoubtedly 

 lead to the molluscs becoming infected with pathogenic organisms " 

 (Wood). Yet we have seen that, apart altogether from the individual 

 susceptibilities or otherwise of the consumer, there are in the series 

 of events necessary to infection many occasions when circumstances 

 would practically free the oysters from infection. This explains the 

 absence of uniformity in degree of contamination, and, coupled with 

 individual susceptibility and degree of cooking, the absence of 

 uniformity in causing outbreaks of disease. 



The sources of pollution of oysters are not the fattening beds 

 alone. The native beds also may afford opportunity for contamina- 

 tion. Then, in packing and transit, and in storage in shops and 

 warehouses, there is frequently abundant facility for putrefactive 

 bacteria to gain entrance to the shells of oysters. 



Dr Klein's researches into this question have been largely con- 

 firmatory of the facts elicited by Dr Cartwright Wood.* Despite 

 the tendency of the bacilli of cholera and typhoid to die out quickly 

 in crude sewage, the sewage is sufficiently altered or diluted at the 

 outfall for these organisms to exist there in a virulent state. We 

 may give Dr Klein's conclusions : 



1. That the cholera and typhoid bacilli are difficult of demonstra- 

 tion in sewage known to have received them. 



2. That both organisms may persist in sea-water tanks for two 

 or more weeks, the typhoid bacillus retaining its characteristics 

 unimpaired, the cholera bacillus tending to lose them. 



3. That oysters from sources free from sewage pollution con- 

 tained no bacteria of sewage (e.g. B. coli communis). Subsequently 

 to these experiments, Klein examined 172 oysters from various 

 layings to which no sewage gained access, and B. coli was absent 



* Special Report of the Medical Officer to the Local Government Board on Oyster 

 Culture, etc., 1896. 



