SHELLFISH 75 



This bacteriological investigation has been directed along 

 three lines: 



A. To enable bacteriology to be used to judge to what 

 extent any given batch of shellfish is dangerous to health. 



B. To enable judgment to be given as to the safety of any 

 given shellfish layings. 



C. To study the conditions under which dangerously con- 

 taminated shellfish can be rendered free from their bacteriological 

 pollution and made safe for human consumption. 



The shellfish chiefly concerned in the bacteriological trans- 

 mission of disease are oysters, mussels and cockles. 



In connection with this subject the general bacteriology of 

 sea water and the sea water of estuaries is of considerable import- 

 ance. 



The bacteriology of oysters in relation to sewage pollution. 



The general bacterial content is of but little significance and 

 the only recorded data of importance refer to the extent to which 

 oysters contain the organisms used as bacterial indicators of 

 sewage. The following examples from Houston's work 1 give an 

 excellent idea of this as regards oysters from different sources. 



(a) Deep sea oysters. Samples were examined from a num- 

 ber of different sources. A very few organisms partially resem- 

 bling B. coli were isolated. Houston concludes : " Judging from 

 these experiments as a whole, the conclusion seems inevitable 

 that in deep sea oysters derived from deep sea water remote 

 from sewage pollution B. coli and coli-like microbes and also the 

 spores of B. enteritidis sporogenes are either absent or, at all 

 events, seldom detectable. The same is true of the surface water 

 over such oysters." 



"B. coli and B. enteritidis sporogenes seemingly form no essential 

 part of the bacterial flora of pure sea water, and they have no 

 part in the economy of the oyster." 



(d) Oysters from estuaries not exposed to serious sewage con- 

 tamination. The Helford River traverses a sparsely-populated 



Royal Comtnission on Seiuage Disposal, Fourth Re for I, 1904, vol. in. 



