57 



Whereas in the oysters not kept in sea water the decrease, 

 though progressing, was distinctly slower ; after four days 

 dry the oyster still contained more B. coli communis (2625) 

 than the wet oyster after one day change in clean water. 



There can, then, be no question about the fact that the 

 oyster per se is capable of dealing with the B. coli communis 

 in the same manner as with the B. typhosus, mz. t that 

 also the B. coli communis does not multiply in the oyster ; 

 when taken in from the surroundings by oysters clean at 

 starting the number of B. coli communis decreases, and if 

 the oysters are kept in clean water the microbe rapidly 

 disappears. 



I consider this additional definite proof that the B. coli 

 communis is as foreign to the oyster as the B. typhosus, and 

 that therefore when B. coli communis is found in oysters it 

 is derived from the surroundings, and must be of fairly 

 recent importation. 



EXPERIMENT VIII. 



In order to obtain further confirmation, the next experi- 

 ment was made in the same manner, but this time with 

 native oysters of a different kind, viz., Colchester oysters. 



One of these oysters (1), immediately on receiving them, 

 was well brushed and cleaned on the outside and then used 

 in the usual manner for analysis, -j 1 - part of the body of the 

 oyster being used for a Drigalski plate. The others were 

 placed in sterile sea water in a fresh tub. No colonies of B. 

 coli came up in the plate of oyster (1). 



After 24 hours in clean sea water we took out a further 

 oyster (2), ^ part of the oyster body being used for a Drig- 

 alski plate. No colonies of B. coli came up in this plate. 



We now infected 2000 c.c. of sterile sea water with one 

 gram of fecal matter of a healthy person. By making a 

 Drigalski plate on the same plan of dilution as in Experi- 

 ment VII, it was ascertained that each c.c. of this water 

 contained 22,000 colonies of B. coli communis that is to 



