SHELLFISH 83 



B. Methods of sampling and dilution. These differ slightly 

 according to the shellfish. 



Oysters. The most thorough method for the bacteriological 

 examination of oysters is that used by Houston for his work 

 for the Royal Sewage Disposal Commission. The procedure is 

 briefly as follows: . 



1. The outside of the oyster-shells are well scrubbed with 

 soap and water, and cleaned as thoroughly as possible in running 

 tap-water, finally with sterile water. 



2. The hands of the investigator are thoroughly cleaned, 

 washed in I in 1000 corrosive sublimate solution, and finally with 

 sterile water. 



3. The oysters are opened by a sterile knife held in position 

 by a sterile cloth, and with the concave shell underneath. Great 

 care must be taken to avoid any loss of the liquor. The liquor in 

 the shell is poured into a sterile loooc.c. cylinder, and the oyster 

 and oyster liquor are added after the oyster has been cut into 

 small pieces by sterile scissors. 



4. Ten oysters are to be treated as above in each experi- 

 ment. 



5. The volume of oyster + oyster liquor is read off, and 

 usually varies between 80 and 1 20 c.c. For qualitative work 

 100 c.c. may therefore be taken as a fair average of the total 

 shell contents of ten oysters. 



Sterile water is then poured into the cylinder up to the 

 loooc.c. mark, and the whole well stirred with a sterile rod. 

 Each 100 c.c. of this liquor may be considered to contain the 

 bacteria in one oyster. 



10. Various amounts and fractions of this liquor are used 

 for the examination for B. coli, B. enteritidis sporogenes, and for 

 streptococci. 



Mussels. The most satisfactory method is one similar to the 

 above, the whole mussel being used. The mussels are thoroughly 

 cleaned, also the hands of the investigator, as for oyster examina- 

 tions, while the procedure is quite similar after the shellfish are 

 opened. 



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