84 BACTERIOLOGY OF THE OYSTER. 



It is said that the soft-shelled clam does not hibernate during the 

 winter. The second quotation from Mitchell's paper, namely, that 

 the oxygen requirement in the common clam is higher than in the 

 oyster may account for this phenomenon. The sooner the available 

 quantity of oxygen is used up, the more quickly will the mollusc open 

 to renew its supply. 



SUGGESTED CHANGES IN STANDARD METHODS OF 

 SHELLFISH EXAMINATION. 



The Second Progress Report of the Committee on Standard 

 Methods of Shellfish Examination recommends that "twelve oysters 

 of the average size of the lot under examination, with deep bowls, 

 short lips and shells tightly closed, shall be picked out by hand and 

 prepared for transportation to the laboratory." . . . 



"Bacterial counts shall be made of a composite sample of each lot 

 obtained by mixing the shell liquor of five oysters." . . . 



Under the heading of "Methods of Rating Oysters for B. coli," 

 the following statement is made: "The following values shall be 

 assigned to the presence of bacteria of the B. coli group in each of the 

 five oysters examined." Then follows a statement and illustration 

 of the method of scoring as adopted by the American Public Health 

 Association. It is clear at once that if we mixed the shell liquor of 

 the five oysters and examined it as a composite sample, it would be 

 impossible to assign values "to the presence of bacteria of the B. coli 

 group in each of the five oysters examined," for the composite sample 

 must be treated as the juice of a single oyster. It is evident that a 

 composite sample is not what is intended, but rather that each oyster 

 shall be examined separately. 



Some workers have based their analysis upon several composite 

 samples of five oysters each, while others have used five, t6n or fifteen 

 oysters separately. There is great variation in the bacterial content 

 of oysters from the same lot. In one oyster there may be one 

 hundred B. coh per cubic centimeter of the shell liquor, while in 

 another oyster from the same sample they may be entirely absent. 

 The important consideration in the examination of oysters is the 

 average number of B. coli in the oysters as a whole and not the number 

 in any individual oyster. For this reason the larger the sample, 

 within reasonable limits, the more accurate the results as an indication 



