66 BACTERIOLOGY OF THE OYSTER. 



for sometime, but not for indefinite periods. It also appears that 

 the closure of the shell is not due to cold rigor or loss of control of the 

 adductor muscle, for at a temperature of 1.5°C. the oyster can open 

 and close its shell with the same ease as at higher temperatures. 



In the following experiments only the shell liquor was used. The 

 method of examination of the oysters was the procedure recom- 

 mended by the Second Progress Report of the Committee on Standard 

 Methods of Shellfish Examination of the American Public Health 

 Association. The medium used was lactose-peptone bile and the 

 tubes were inoculated in duplicate. The tubes were examined every 

 twenty-four hours for three days. If ten per cent, or more of gas 

 appeared during this time, it was considered to show the presence of 

 intestinal bacteria. Unfortunately in the first experiment the 

 investigation had to be discontinued after November 29th, so that 

 we have only the results extending over 12 days. 



Experiment I. 



November 16, 1912, about a bushel of polluted oysters were taken 

 from the Providence River and the following day were transferred to 

 Wickford Harbor. They were laid upon clean sandy bottom on the 

 edge of the channel and were well separated to allow free access of 

 water. The temperature of the water at the time of taking the 

 oysters was 14°C. The average of the maximum and minimum 

 temperature at Wickford for November 16 and 17 was 6.5°C. 

 A sample of the oysters was taken at the time they were placed in 

 Wickford Harbor and the analysis showed a score on fifteen oysters of 

 870. Samples were shipped to the laboratory every day until 

 November 29th. These were analyzed immediately so that only 

 three or four hours elapsed between the time of collecting the sample 

 and the time of analysis. The following table shows the results of 

 the analysis of fifteen oysters on the different days. The temperature 

 is the average of the maximum and minimum temperature as recorded 

 at the lobster hatchery of the Inland Fish Commission which was 

 located nearby. 



