24 SHELLFISH CONTAMINATION FROM SEWAGE-POLLUTED WATERS. 
LABORATORY RESULTS ON FLOATED OYSTERS. 
Some results of laboratory experiments on the vitality of B. colt and 
B. typhosus in salt solutions of various strength are as follows: 
Saturated salt solution (c. p. sodium chlorid) inhibited growth of 
B. typhosus after three hours exposure, B. coli and M. aureus after 
six hours. 
A 25 per cent solution of salt was sufficient to retard development 
of the typhoid bacillus, B. coli, and M. aureus in nutrient beef broth. 
Growth occurred with lower dilutions. | 
From the investigations made it appears that oysters grow best to 
maturity in water containing from about 1 to 3percent seasalt. Above 
or below this amount they do not thrive so readily; in fact they perish 
Fic. 6.— Oyster floats located near a shucking establishment. The small building in the foreground is a 
privy used by 100 to 150 men. The drainage from this vault seeps through the loose soil and wooden wall 
into the water which bathes the fioats. Drainage from decaying shell heaps and the washings from 
these oysterhouses likewise flow into this same water. Analysis of this water and oysters on the floats 
showed contamination 
when kept for any length of time in waters showing an appreciable 
variation from these figures. On this poimt Nelson,* of the New 
Jersey experiment station, says that the period of viability is greatest 
in water having a saline content of about 2 per cent, but for old 
oysters the figure is higher. He further says that oystermen should 
not be required to freshen oysters, but that this should be done by 
the caterer just before cooking. 
There seems to be no objection to drinking oysters in waters of the 
same saline content as those in which they will grow to maturity, 
provided there is no possible source of contamination. 
One of the greatest dangers arising from the practice of floating 
oysters is the fact that they are often consumed raw, and if polluted, 
they become active factors of disease dissemination. As is shown in 
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