SEWAGE CONTAMINATION OF OYSTER BEDS. 235 
ANALYSIS OF OYSTERS FROM UNPOLLUTED SOURCES WHICH HAVE BEEN 
PLACED FOR A TIME IN POLLUTED WATER. 
In connection with the above work, 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 oyster companies controlling beds in the lower river 
and bay 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 water 
in the vicinity of these wharves is filled with all sorts of organic 
refuse, which passes down the river in a slow stream by the docks. 
After the oysters have been dredged in the river below, they are 
brought immediately to the city, and are very often dumped into 
shallow cars moored close by the oyster houses, where they 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 days, 
and thus have plenty of time to take in a good supply of sewage 
bacteria, even though they were 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 2. coli 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 
2or3 examined. The other batch was 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 days, however, this organism was readily isolated 
from the juice of all 5, though it was 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 which 
BL. coli is occasionally found. The tides and wind have considerable 
effect upon this section, since evidence of sewage pollution has been 
found only when samples were collected at very nearly low water. 
The waters of Providence River and Narragansett Bay from locali- 
ties more than 8 miles distant from the principal sewers that discharge 
into this basin do not contain sewage matters, and do not give positive 
tests for B. colt. 
