BACTERIOLOGICAL DATA. 



35 



they were well scrubbed, dipped quickly in boiling water, and opened 

 with sterile instruments, the liquor from each oyster being collected 

 in a separate sterile petri dish. Quantities of 1 cc, 0.1 cc, and 0.01 cc 

 of shell liquor were planted in lactose-peptone ox-bile fermentation 

 tubes, and incubated in the same manner as was observed in making 

 the water analysis. B. coli were also isolated and studied in pure 

 culture in the same manner as in the case of water. 



The method of scoring oysters was the same for all the samples 

 herein submitted, and is that recommended and known as "The 



MONTHLY 



O/V SHELL 



SCORE. 



32O 



230 



/4O 



50 



4/ 



32. 



23 



SO SAMPLES 



1 



V4f?/O(/S SOt/ffCES. 



SCORE. 



320 



230 



/4O 



SO 



23 



FIG. 7. Average monthly score on shell oysters from different sources. 



American Public Health Association Method of Scoring Oysters for 

 B. coli," summarized as follows: 



The presence of B. coli in each oyster of the five examined is to be given the following 

 values, which represent the reciprocals of the greatest dilutions in which the test for 

 B. coli is positive: 



If present in 1 cc but not in 0.1 cc, the value of 1. 



If present in 0.1 cc but not in 0.01 cc, the value of 10. 



If present in 0.01 ce but not in 0.001 cc, the value of 100, etc. 



The addition of these values for the five oysters would give the total numerical value 

 for the sample and this figure would be the score for B. coli. 



Monthly average scores for oysters from various sources and from Jamaica Bay are 

 shown on figure 7. 



