RESULTS of a reinvestigation of the cleansing effect of changing sea water on contaminated oysters was reported in the March, 1926, issue of the JOURNAL. Two experiments were made-one in a tank, the other in natural waters.The tank experiment showed that there was a very miarked reduction in the number of B. typhosus on or in contaminated oysters after 3 changes of sea water. However, B. typhosus in small numbers could still be isolated after 18 changes of sea water covering a period of 24 days. This experiment was not wholly satisfactory for several reasons: First, apparently due to insufficient aeration, the oysters started to die after the 15th day and the experiment was terminated by the lack of further viable oysters. Second, although the temperature maintained was satisfactory for drinking, the volume of changing water was in no way comparable to the volume of change which tidal flow would give under natural conditions with resulting wash effect and dilution. These considerations made it seem that the rate of cleansing in tanks must be materially slower than in natural waters. We, therefore, looked for a place where contaminated oysters might be returned to their natural waters without creating a menace. The water was too cold at this time (December and January) to insure active drinking, but it seemed desirable while waiting for appropriate temperatures to determine the viability of B. typhosus on or in hibernating oysters.Oysters, native to the waters to be used, were accordingly contaminated by drinking them in sea water to which feces containing B. typhosus had been added. The contamination was light. The oysters were returned to their waters. After 24 hours B. typhosus could not be isolated from the shells. The liquors became negative between the 10th and 17th days. Enrichments of the pooled gills were still positive on the 5 1st day, when the supply of oysters was exhausted. With the onset of warmer weather we repeated the above previously reported experiment.[481
IN THE February issue of the JOUR-NAL, our experiments on the effect of chlorination on oysters contaminated with typhoid bacilli were reported. Through the exigencies of time and available JOURNAL space the collateral experiments on the effect of changing sea water alone were not presented. These as well as observations on the effect of dry storage were held for report at this time.When the increase of typhoid fever occurred during the latter part of 1924, it was noticed coincidently in inland as well as seaboard cities. When investigations showed that this increase of typhoid fever was attributable to contaminated oysters it indicated that B. typhosus must persist in dry, stored oysters for some time. Experiments were undertaken, therefore, to determine the time of survival of B. typhosus under storage conditions.Oysters for these observations were dredged at West Sayville, Long Island, and sent immediately to the laboratory. The water was obtained from Great South Bay, Long Island.Two lots of about 80 oysters were contaminated by suspending the oysters in wire crates in tanks containing about 8 gallons of contaminated sea water: Lot A, shown in Table I, in sea water contaminated by the addition of a suspension of feces containing B. tvlphosus; Lot B, shown in Table II, in water contaminated with freshlv isolated cultures of B.tvpShosus. The tanks were kept overnight at room temperature (18 to 22°C.).The oysters drank actively. Thev were then removed from the tank for storage. The storage conditions approximated in temperature that of the colder months (February and March) of the oyster season. The oysters were kept out-of-doors in a small shed on the north side of a building which was covered with snow.
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