BACTERIOLOGY OF THE OYSTER. 63 



The important conclusion to be drawn from this series of experi- 

 ments is that under the conditions of the experiment bacteria of the 

 B. coh group do not materially increase or decrease in oysters in the 

 shell during storage. 



CLEANSING OF POLLUTED OYSTERS. 



As soon as the etiological connection between oysters and certain 

 epidemics of typhoid and gastro-enteritis was firmly established, the 

 question at once arose as to how long a time it would take oysters 

 known to be polluted to free themselves from sewage organisms after 

 they had been removed to water free from sewage contamination. 



Klein^ put oysters into tanks in the laboratory and infected them 

 withB. typhosus. About one-third of the water was removed every 

 day and replaced with clean sea water. Oysters were removed at 

 various intervals and examined for B. typhosus. The experiments 

 were repeated several times and B. typhosus was isolated at the end 

 of the experiment in every case. The various experiments were con- 

 cluded on the seventh, ninth, fourteenth, sixteenth, seventeenth and 

 eighteenth day after infection. The bacilli were isolated from the 

 sea water twenty-one days after the beginning of the experiment. 

 Of course, these experiments did not approximate natural con- 

 ditions and so we can draw no definite conclusions from them regard- 

 ing the length of time necessary for oysters to rid themselves of these 

 bacteria when taken from polluted areas and re-layed in water free 

 from pollution. 



Herdmann and Boyce^ tried the experiment of infecting oysters 

 artifically with large numbers of B. typhosus and then subject- 

 ing them "to a running stream of pure clean sea water." 

 Eighteen oysters were infected and examined at different intervals 

 varying from one to seven days. Only the stomach contents were 

 examined and considerable allowance must be made for this, for the 

 writer has sho^vn in another part of this paper that the number of 

 bacteria contained in the stomach are quite insignificant compared 

 with the number in the shell liquor and on the body of the oyster. 



In three of the eighteen oysters examined which had washed for 

 three, five and seven days, respectfully, no typhoid bacilli were 

 found. In the other fifteen oysters examined B. typhosus was 



'Relation of Oysters and Disease, Supplement to the Report of the Medical Officer to the Local 

 Government Board, 1893. 

 ^Loc. cit. 



