24 BACTERIOLOGY OF THE OYSTER. 



For this reason the mouth of the ordinary water sample bottle is not 

 large enough to collect all the juice and so in most laboratories a 

 sterile petri dish is used for the purpose. This would preclude the 

 possibility of shaking. Now if shaking of a water sample, which 

 to the eye is perfectly clear, is advisable to break up the clumps of 

 bacteria and give a more even distribution of bacteria, what can be 

 said of the juice of the oyster which has a decided milky appearance 

 and which usually contains strings and flakes of mucus large enough to 

 be seen several feet away? If one plates a cubic centimeter of this 

 mixture without shaking, the flakes will appear in the solid medium 

 as irregular, opaque particles. The probabilities are from the 

 writer's experience that the flakes of mucus carry a large number of 

 bacteria and we have a large confluent mass of colonies developing 

 around each mucus flake. Even if flakes are not present, laree 

 confluent masses of colonies from the size of a penny to the size of a 

 quarter develop, which render counting impossible. Usually, how- 

 ever, only bile tubes are used for the presumptive test for B. coli and 

 no plates made so that this clumping is not noticeable except where 

 bile tubes do not duplicate or where one gets a positive test in the 

 1-lOth c.c. or 1-lOOth c.c. dilution and not in the 1 c.c. or a positive 

 presumptive test in the 1-lOOth c.c. dilution and not in the 1 c.c. 

 or 1-lOth c.c. dilution. In a study of about 2,000 tubes in the pre- 

 sumptive test the writer found that they duplicated only about two- 

 thirds of the time and that in one set one might get a positive presump- 

 tive test in the 1-lOOth c.c. dilution and in the duplicate set only in the 

 1 c.c. dilution or not at all. 



Aside from the part played by the mucus in oyster juice the part 

 played by the mucus left upon the body of the oyster is, generally 

 speaking, much more important. Often much more mucus is left 

 upon the body of the oyster than is found in the oyster juice. As the 

 mucus is the part which catches the bacteria and holds them, it follows 

 that often more bacteria are left upon the oyster's body than are 

 found in the oyster juice. Hence, it follows that, if we only examine 

 the juice of the oyster we are only finding a fraction of the bacteria 

 really present in the oyster. These facts will be brought out more 

 clearly when the experimental work upon which these statements 

 are based, is taken up. 



The idea of comparing the number of bacteria found in the shell 

 liquor with the number that can be "washed" from the body of the 



