63 



section), viz., that oysters derived from " clean " layings, or 

 sea water taken many miles away from the shore, contained 

 large numbers of the true B. coli communis, are to me 

 perfectly unintelligible. I must confess I have not suc- 

 ceeded in verifying this. I have not found, for instance, 

 that oysters coming from layings which are miles away from 

 any source of sewage or manure pollution, e.g., some layings 

 in Halford Eiver, some layings in Hayling Island, " contain 

 1000 B. coli communis per oyster" (see Eeport of Sewage 

 Commission) ; in fact, I have not found anything approaching 

 such a condition even in oysters directly from sewage-bathed 

 ponds.* I have quite recently had the opportunity to examine 

 oysters which came from the mouth of Langston Harbour, only 

 600 yards distant from the principal sewer outfall of Ports- 

 mouth, and what I found was that of nine oysters examined 

 all contained B. coli communis. But in what numbers ? 

 Three were specially tested by Drigalski plates each made 

 with one-fiftieth part of the body, and they were found to 

 contain : one 200 but not 300 B. coli communis per 

 oyster, a second one 150 but not 200 B. coli communis 

 per oyster, and a third 50 only. A sample of oysters 

 derived from layings several miles away from the above 

 showed B. coli communis only in one out of nine oysters, 



* The culture tests for B. coli communis of faecal matter of man and of 

 ordinary domestic sewage are these : 



1. B. coli communis forms on Drigalski medium at 37 C., after 24-36 

 hours, colonies several millimetres in size, distinctly red, with distinct 

 red halo when viewed in transmitted light. 



2. In ordinary nutrient gelatine shake culture it forms colonies all 

 through the medium with numerous gas bubbles already in 24 hours 

 at 20 C. ; in gelatine streak it forms at 20 C. a rapidly spreading 

 dry band with irregular margin ; no liquefaction of gelatine at any 

 time. 



3. Neutral red broth at 37 C. is changed in 24-36 hours from cherry red 

 to greenish fluorescent. 



4. It turns MacConkey fluid (litmus, glucose, taurocholate of soda, pep- 

 tone) red, forming acid with numerous gas bubbles. 



5. It grows well in phenol broth at 37 C., making it turbid in 24 hours 

 with copious gas formation. 



6. It produces indol in nutrient broth at 37 C. in 3-5 days. 



7. It turns lactose peptone litmus in 24-36 hours at 37 G. red (acid 

 production) with copious gas formation. 



8. Litmus milk at 37 C. becomes red in 24 hours, due to acid production, 

 the milk becoming clotted in 1-3 days. 



