204 THE SEA FISHERIES 



with the results of oiir own investigations and local inquiries, we 

 are strongly ot opinion that the only way in which this evil can be 

 effectively dealt with is by placing tidal waters under the juris- 

 diction ot some competent authority, and conferring on that 

 authority power to prevent the taking of shellfish for human con- 

 sumption from any position in which they are liable to risk of 

 dangerous contamination, and to enforce restrictions as regards 

 waters, foreshores, pits, ponds, beds and layings in which shellfish 

 are fattened or stored as and when required." The fact that over 

 fourteen years have elapsed since this report was published, and 

 nothing has been done to carry out the recommendation, justifies 

 further consideration of the question. 



Bacteriological investigations which have been made from time 

 to time, notably by Klein and Johnstone, have proved that con- 

 taminated shellfish when placed in clean sea water are able to clean 

 themselves rapidly, and after a varying period, depending on the 

 degree of infection, the mollusc is found to be almost free from 

 bacteria. Klein 's'^ experiments were conducted with oysters more 

 particularly, and these bivalves were infected both with the bacillus 

 coli communis, which is normally present in sewage, and the bacillus 

 typhosus, the specific organism of typhoid or enteric fever ; in 

 both cases the self -cleansing was rapid and efficient. From this it 

 was concluded that the ordinary moUusca do not afford a nidus 

 for the growth and propagation of bacteria. As it seems well 

 established that moUusca from reasonably clean, not absolutely 

 sterile, sea water are quite innocuous, it is all the more remarkable 

 that consignments from beds which are known to be polluted can 

 be, and are, placed on the markets with impunity. 



Johnstone^ states that in the estuaries of the coasts of Wales 

 and Lancashire contamination of the shellfish only occurs at or 

 about low water. At this period of the tide the channels are usually 

 very narrow and shallow, and the extent to which the sewage is 

 diluted with sea water is small, while the sewage may float on the 

 surface and may flow over mussels which come dry at low water, 

 direct contamination resulting. The tidal currents are ™1 ^ so 

 strong that after a couple of hours' flood the sewage has become 

 diluted to an enormous extent, and the water may be regarded 

 as free from serious contamination. 



. Experiments and observations on the vit^ty "^ 'V^S^orl'inll^ioi 

 and of sewage microbes m °5^ters and ^ber sheM^^^^ Inv g 

 the Worshipful Company of ^^^^'^°^^^ffjJ^J,^u f^ the Lancashire and Western Sea 



. ^m Quarterly Report ^^^l-^f^J^cl {914. See^so, " The methods of 



^^^^^^^^^^^^^^^-^^^^'^^^ ^'''- """"• '" "'''■ 

 Lab., No. 23. V- 57. 1915- 



