BACTERIOLOGY OF THE OYSTER. 85 



of theB. coli content of the oysters of any particular area. Smith/ 

 in the analysis of one hundred and twenty-five oysters in each of a 

 series of samples, came to the conclusion that not less than fifteen 

 oysters should be used. The use of too small a sample may account 

 in part for the wide variation in results obtained by different analysts 

 in the examination of the same oyster bed at approximately the same 

 time. In the writer's opinion twenty-five oysters is not too large a 

 sample to be used in any analysis. 



The changes which the writer would suggest in "Standard Methods 

 of Shellfish Examination," are as follows: 



The size of the sample should be at least twenty-five oysters. 

 After reaching the laboratory the oysters should be scrubbed 

 thoroughly with a stiff brush in water free from B. coli and dried. 

 When ready for examination the oyster should be held between the 

 thumb and the fore-finger and the lip of the shell flamed in the bunsen 

 burner or burned off with alcohol. The opening should be done with 

 an oyster knife which has previously been burned with alcohol. The 

 method of drilling a hole through the shell and pipetting out the 

 oyster juice should never be substituted as an alternative method. 



The shell liquor of the five oysters of each of the five composite 

 samples should be collected in sterile, graduated, glass-stoppered 

 bottles and the bodies of the five oysters should be placed in a wide- 

 mouth, glass-stoppered bottle. The amount of shell liquor should 

 be read off and an equal amount of sterile one per cent, salt solution or 

 sea water added to the bottle containing the bodies of the oysters. 

 The stopper should be replaced and the bottle shaken at least one 

 hundred times. (The writer's experience has been that, if the oysters 

 are opened carefully so as to avoid mutilation, the bodies of the oysters 

 are damaged but very little by this procedure unless the shaking is 

 especially vigorous.) The salt solution and mucus should then be 

 decanted into the bottle containing the shell liquor and the whole 

 shaken vigorously one hundred times to break up any clumps of 

 bacteria and to separate as far as possible the bacteria from the bits 

 of mucus. The five sets of oysters should be treated in this manner, 

 making five samples of five oysters each. If the operation is conducted 

 properly there should be an equal quantity of shell lifiuor and salt 

 solution in each of the five composite samples. 



^Size of the Sample Necessary for the Accurate Determination of the Sanitary Quality of Shell 

 Oysters, American Journal of Public Health, HI, 1913, 705. 



