146 BACTERIOLOGICAL METHODS 



disturbances which results from the eating of such flour, is the 

 proper warning. The presence of a limited number of colon bacilli 

 in foods and drinks is the danger mark and not the actual occur- 

 rence of cholera, of typhoid, of dysentery, due to the eating of 

 more highly contaminated foods. The danger signal must be 

 within the zone of safety and not beyond it. 



The methods for the bacteriological examination of shellfish 

 are but modifications of the methods used in the examination of 

 water supplies. As in the case of drinking water, the chief index 

 to the pollution of shellfish is the colon bacillus test. The examina- 

 tion of the water source above the oyster beds very frequently 

 gives inferential information as to the possibility of the contami- 

 nation of the shellfish which obtain their food supply from beds 

 flooded by such waters. The following is the method for the 

 bacteriological examination of shellfish adopted by the American 

 Health Association at the 191 2 meeting. 



1. Selection of Sample. — Twelve oysters of average size of the 

 lot to be examined, having deep bowls, short lips and shell tightly 

 closed, are picked out by hand or by means of a sterilized long- 

 handled spoon and prepared for immediate transportation to the 

 laboratory. 



2. Making a Record of the Sample.^ — This record should cover 

 the following points. The exact location of the bed from which the 

 sample was taken.- The depth of the water at the time the oysters 

 were gathered. Weather conditions, direction and velocity of 

 wind, state of tide, day and hour when the stock was taken from 

 the water, the conditions under which the stock had been kept 

 since removal from the water and up to the time when the sample 

 was taken, presence of abnormal odors, temperature of stock, and 

 the day and hour of taking the sample. 



3. Transportation of the Sample. — The sample oysters are to 

 be packed in a suitable metal or pasteboard container of the size 

 and shape convenient for shipping. The important points to bear 

 in mind are : the prevention of the mixing of the oyster liquors of 



