F. S. Wright U9 



in the human colon {Bacillus coli communis etc.), often in numbers too 

 great to be ignored. Mussels may also contain through inhibition of 

 contaminated water, ^^ Bacillus typhosus (producing enteric fever), and, 

 possibly B. enteritidis (producing Gaertner poisoning)." These last are, 

 luckily, much more rare in this connection. Even though we need not 

 place implicit trust in the findings of bacteriological science, which has 

 to rely upon indirect methods or reactions in its determinations of these 

 minute organisms, yet we see that the matter is serious enough. It is 

 probable that (admitting the validity of their identification), their 

 sojourn in the mussels' digestive tract, or in salt or brackish water, 

 may have so changed the character of the bacteria as to render them 

 generally harmless to man, or, at least, less harmful. 



It will be remembered that, in a previous paragraph, it was stated 

 that the water in the Cardigan Bay estuaries was never wholly changed 

 in any one tide. Thus, impurities washing about in the river bed may 

 remain there for a considerable tirne, and the significance of this factor 

 now becomes apparent. Under such conditions (which affect the areas 

 now being discussed), the occurrence of, for example, a single case of 

 enteric, could bring about an immediate cessation of the fishing in the 

 place aft'ected. Therefore, it becomes necessary to effect the purifica- 

 tion of the shellfish in order to safeguard the industry, no less than in 

 the interests of the public health. 



A crude method of '"purification" is sometimes practised by the 

 fishermen at certain places. After cleaning ("spinning") the mussels, 

 they are placed in bags, which are left to wash for a day or two in the 

 tide, where the water bathing them is known to be reasonably free from 

 contamination. This rough method cannot be said to have the desired 

 effect, for reasons now to be stated. According to recent views, any 

 bacteria which the mussel may harbour are present in the animal's 

 rectum ; that is, in the faecal matter not yet extruded by the animal. 

 Now, although mussels treated in the manner described above will 

 speedily excrete such waste products, these, being retained by the 

 closely woven fabric of the sacking, only serve to re-infect the shellfish. 



Mussel purification tanks are projected to be erected (one is already 

 in use at Barmouth), in connection with the Cardigan Bay mussel beds, 

 under the supervision of the Lancashire and Western Sea Fisheries 

 Committee. They are solidly built concrete structures, in several com- 

 partments, on the wooden grids on the floor of which the mussels are 

 placed, in layers not exceeding three deep. They are designed to fill 

 over the top at about high water of neap tides, when the mussels will 



