SHELLFISH 1 47 



the different samples and avoiding the mixing of the oysters with 

 the ice water of the packing ice. The samples must in all cases be 

 placed on ice or packed in ice if they cannot be examined inside of 

 36 hr. or if the outside temperature is above 50° F. It is, however, 

 not necessary to place the oysters in absolutely tight containers 

 provided the above conditions are maintained. 



4. Laboratory Procedure. — Record the date of receiving the 

 sample, condition of seals, of the sample oysters and the tem- 

 perature of the interior of the container at the time of opening. 

 The bacteriological examination should in all cases be started as 

 soon as possible after the receipt of the sample. 



Before beginning operations the hands must be thoroughly 

 scrubbed and all vessels to be used must be steriHzed. The shell 

 of the oyster may be opened by means of a sterilized oyster knife 

 or by drilling a hole through the shell near the hinge. The drill 

 must be sterilized and the area of the shell to be operated upon must 

 be cleaned, flamed before drilling and flamed at least once more 

 during the drilHng process. 



The simplest and quickest method for opening the oyster shells 

 is that employed by Stiles of the Bureau of Chemistry. By means 

 of a pair of sterilized wire nippers crush and break off enough of 

 the two valves so as to make the use of the oyster knife easy. 



Before opening the oysters see that they are thoroughly 

 scrubbed and then rinsed in boiled (sterile) water, and each 

 oyster is wiped quite dry and flamed before it is opened. 



5. Bacterial Counts. — Bacterial counts are made of the compos- 

 ite sample of each lot obtained by mixing the shell liquor of five 

 oysters. Agar shall be used for the culture medium and in general 

 the procedure shall be in accordance with the method recommended 

 for the examination of water. The water used for making the di- 

 lutions shall contain i per cent, of sodium chloride, in order to 

 approximate the natural salinity of the oyster liquor. The agar 

 plate cultures shall be incubated at 20° C. for 3 days and the col- 

 onies counted in the usual manner. 



