EXAMINATION OF SHELLFISH 255 



beds showed them to be heavily sewage polluted. In 

 December of the same year the analyses of the oysters 

 were strikingly different, although the condition of 

 the water was apparently unchanged. In the examina- 

 tion five oysters were selected in each case and the 

 average total number of bacteria per cubic centimeter 

 was determined and the presence of colon bacilli was 

 tested by the bile tube and subsequent isolation and 

 identification of the organisms. The table on page 256 

 shows the numbers of bacteria found, and the propor- 

 tion of the five oyster samples in which colon bacilli 

 were present in cubic centimeter amounts and also 

 in o.i and o.oi of a cubic centimeter. 



The conclusions arrived at by Gorham are that 

 during the cold weather the oysters assume a condition 

 of rest or hibernation, during which time ciliary move- 

 ment ceases and the process of feeding is suspended. 

 No organisms are therefore taken in from the outside 

 water and those inside the oyster are gradually elim- 

 inated, so that the total number of organisms is 

 reduced very considerably and the oyster becomes 

 practically free from colon bacilli. 



Standard Methods for the Examination of Shellfish. 

 The examination of shellfish for pollution is regarded 

 as of such importance by the American Public Health 

 Association (1912) that a committee was established 

 to report upon methods of examination and estima- 

 tion of the numbers of colon bacilli found. The 

 following abstract of the second report of this 

 committee gives the recommendations for standard 

 methods for bacteriological examination of shellfish 



