32 BACTERIOLOGY OF THE OYSTER. 



^/^oo c.c. of the shell liquor. Gas appearing in these respective 

 dilutions would indicate two, twenty and two hundred B. coli per cubic 

 centimeter instead of one, ten and one hundred as in the procedure 

 of " Standard Methods. " 



The last column gives the combined score, in other words, the score 

 based upon the number of B. coli in both the shell liquor and in the 

 washings. The number of B. coli in each is added together and 

 divided by the number of cubic centimeters of shell liquor. This 

 method makes no allowance for the amount of mucus present on the 

 body of the oyster. This quantity would not exceed one cubic 

 centimeter on the average, for many of the oysters were small. It is 

 more convenient and just as accurate for comparative purposes to 

 ignore this quantity, while it is much more convenient in dividing the 

 total number of B. coli found in the oyster by the quantity of shell 

 liquor. It avoids fractions much more often than would be the case 

 if we added one to the number of cubic centimeters of shell liquor. 

 Occasionally, however, in the combined score, the quotient is not an 

 even number and so the score is made the whole number next above 

 or below depending whether the fraction was less than or more than 

 one-half. Thus if the score came 20.4 it would be called 20; if the 

 fraciton were .5 or more it would be called 21. 



It would seem from these experiments that there is no question that 

 the shell liquor contains many more bacteria than are left on the body 

 of the oyster and that in analysis we could ignore entirely the bacteria 

 left on the body of the oyster. 



These results did not equal the writer's expectation and it was 

 thought that perhaps the treatment of the oyster's body was not suf- 

 ficient to remove all the mucus and bacteria present. Accordingly the 

 following method of analysis was adopted for the subsequent experi- 

 ments : The oyster liquor was collected and diluted in the same manner 

 as before. It was shaken vigorously one hundred times before inocu- 

 lating into agar and bile. The body of the oyster after draining was 

 transferred to a sterile large mouthed, glass stoppered bottle and 

 covered with twenty cubic centimeters of one per cent. NaCl solution. 

 The oyster and salt solution were shaken fairly vigorously one hundred 

 times and the solution of salt and mucus was removed by the pipette 

 or poured into a smaller glass bottle and again shaken vigorously 

 one hundred times. This mixture was then inoculated into the bile 

 tubes and the agar plates. At first one per cent, sodium carbonate 



