SEWAGE COlSTAMINATIOlSr OF OYSTER BEDS, 



227 



After inoculation the 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 laborator}^ twice 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. vul<faius very closely in cultural features 

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

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

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

 culture of B. coli^ and it was found that this organism grew readih' 

 in the carboi gelatin. 



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

 ated, one in the entrance to Mount Hope Bay off Bristol Ferry, and 

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

 October, 1902, of the oystei-s from the bed at the entrance to Mount 

 Hope Ba3^ The results of this work are found in Table XV: 



Table XV. — Analysis of oi/sters from Bristol Ferry. 



Specimens and date of collection. 



Dextrose 

 fermented. 



Red colo- 

 nies on 

 litmus lac- 

 tose agar. 



B. coli. 



other focal 

 bacteria. 



Oysters, October 30, 1902. 



1. Intestine 



2. Intestine 



3. Intestine 



4. Intestine 



5. Intestine 



6. Intestine 



7. Intestine 



8. Intestine 



9. Intestine 



10. Ift testine 



1. Juice 



2. Juice 



3. Juice 



4. Juice 



6. Juice 



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 

 Feriy beds 7 miles from Fall River. Neither ground is contaminated 

 by sewage from that citj^, 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 oj^sters 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. 



