SEWAGE CONTAMINATIOlSr OF OYSTER BEDS. 



227 



After inoculation tlic plates were allowed to develop three or four 

 daj^s at room temperature and then examined for growths of B. coli. 

 The oysters used were received in the laboratory twi<ie a week during 

 October, Noveml>er, and December of 1902, and the specimens were 

 opened within eight hours after they had been taken from the water. 

 The intestines of 200 oysters were examined in this manner. After a 

 week's growth all but 3 of the 200 plates remained sterile. The colo- 

 nies developing on these 3 were those of a large spore-forming aerobic 

 bacillus, which resembled B. vidgatus very closel}" in cultural features 

 and bore no resemblance to B. coll. Some time after these experi- 

 ments were carried on a series of control pLates (nutrient gelatin 

 containing 0.05 per cent carbolic acid) were inoculated with a known 

 culture of B. coU^ and it was found that this organism grew readily 

 in the carbol gelatin. 



The two remaining beds visited in the course of this work are situ- 

 ated, one in the entrance to Mount Hope Ba}' off Bristol Ferry, and 

 the other in the Kickemuit River. One examination was made in 

 October, 1902, of the oysters from the bed at the entrance to Mount 

 Hope Ba}". The results of this work are found in Table XV: 



B. coli was found in the juice of but two specimens and in the intes- 

 tines of a single one. The Kickemuit River beds are 4^ and the Bristol 

 Ferrj" beds 7 miles from Fall River. Neither ground is contaminated 

 by sewage from that cit}^, and the slight pollution found at Bristol 

 Ferry is due to local causes. Four batches of oysters were obtained 

 from Kickemuit River. In all, 20 oysters were examined, and it was 

 found that B. coll was not present in the intestines or juice of these 

 specimens. 



The foregoing anal3^ses demonstrate the following facts: 

 Oysters, clams, and mussels taken from the Providence River or its 

 shores within half a mile of the Fields Point sewer outlet contain B. 

 coli and other fecal bacteria within their shells. 



