SEWAGE CO]!TTAMIlSrATION OF OYSTER BEDS. 235 



ANAI;YSIS OF OYSTERS FROM UNPOLLUTED SOURCES WHICH HAVE BEEN 

 PLACED FOR A TIME IN POLLUTED WATER. 



Ill connection with the above Avork, it has been interesting to note 

 the effect produced on uncontaminated oysters by allowing- them to 

 stand for a time in water highly charged with sewage matters. A 

 number of the 03"ster companies controlling beds in the lower river 

 and ba}^ have docks and opening houses bordering on the Seekonk 

 River, in the neighborhood of the outlet of one of the small sewers 

 draining the east side of the city of Providence. At times the w^ater 

 in the vicinity of these wharves is filled with all sorts of organic 

 refuse, which passes down the river in a slow stream b}' the docks. 

 After the oysters have been dredged in the river below, they are 

 brought immediatel}' to the city, and are very often dumped into 

 shallow cars moored close bv the 03"ster houses, where the}- are allowed 

 to remain in the filthy river water until the openers are in need of new 

 material. They often remain in these cars from one to three daj^s, 

 and' thus have plenty of time to take in a good supply of sewage 

 bacteria, even though they w^ere not infected when first brought to 

 the city. 



Two batches of oysters that had lain in floats in the Seekonk River 

 for a time were subjected to the same tests used in this work on fresh 

 material. One batch of 5, dredged off Warwick Neck, had lain sixteen 

 hours in one of these floats. As has already been shown, Warwick 

 Neck oysters are not infected with B. coll or other sewage bacteria 

 when taken from the beds, but the juice of these 5 specimens gave 

 positive reactions for this organism; it was found in the intestines of 

 2 or 3 examined. The other batch w^as brought up from the Kicke- 

 muit River, whose beds also are free from sewage pollution and are 

 not infected with the colon bacillus. After these oysters had lain in 

 the car for two daj^s, however, this organism was readily isolated 

 from the juice of all 5, though it w^as not found in the intestines of 

 any of them. Water samples taken in these cars also contained 

 B, coli. 



CONCLUSIONS. 



The sewage-contaminated area of the Providence River extends 

 downstream from the outlet of the city sewer at^ Fields Point, a dis- 

 tance of about 5 miles. Below this area is a section about 2 miles 

 wide, extending from one side of the river to the other, in w4iich 

 B. coli is occasionally found. The tides and wind have considerable 

 effect upon this section, since evidence of sewage pollution has been 

 found onh^ when samples were collected at very nearly low water. 



The waters of Providence River and Narragansett Bay from locali- 

 ties more than S miles distant from the principal sewers that discharge 

 into this basin do not contain sewage matters, and do not give positive 

 tests for B. coli. 



