22 SHELLFISH CONTAMINATION FROM SEWAGE-POLLUTED WATERS. 



This process of treating oysters in the shell is variously described 

 as " fattening," "feeding," "freshening," "floating," "bleaching," 

 "drinking," or "plumping." By careful observation one can see 

 oysters on these floats open and close their shells, especially at the 

 beginning of flood tide. The least sudden jar or visible shadow will 

 cause them to close their shells immediately. 



The method of floating oysters as ordinarily practiced is not a 

 true fattening process, but is only a means of increasing the bulk of 

 the oyster by adding to the water content and gives it a lighter color. 

 These changes are brought about by osmotic action caused by the 

 oyster being removed from comparatively salt water to a fresher 

 medium, and they will not occur when the oyster is floated in water 

 of the same saline content as that in which it was grown. Should 

 the water in which these floats are placed be polluted with sewage 



FIG. 4. Two oyster floats anchored in the rear of oysterhouses. Privy vaults are located in the rear of 

 these buildings, refuse being dumped directly into the river. It is a crime punishable by $100 fine to 

 float oysters in this river. An epidemic of typhoid occurred some years ago from oysters floated in 

 this place. 



it is easy to see how the oyster may also become contaminated. 

 Oysters may increase in bulk from 10 to 25 per cent or more when 

 floated or when washed sufficiently long in running fresh water after 

 shucking. This variable increase in bulk depends upon the salinity 

 of the water from which the oyster was previously removed, the 

 length of time that the floating or washing is continued, and the 

 character of the water in which they are floated or washed. Shucked 

 oysters from salt water increase in bulk the same as when in the shell 

 if soaked in a plentiful supply of fresh water. On the other hand, 

 plumped oysters, taken from '''brackish water," when placed in 

 comparatively salt water, will decrease in bulk according to the 

 saltiness of the water and previous treatment. 



In the course of this investigation many localities were visited 

 where oyster floats were in operation, and in only a very few instances 



