328 SEWAGE AND ITS PURIFICATION 



sewage discharging therein, or even to ensure the non-coli 

 environment of the oyster beds themselves. Such steriHzation 

 is on the principle I have always advocated — that it should be 

 as near the consumer as possible, and should be confined to the 

 thing consumed. Actual details have to be worked out for the 

 particular industry. The similar removal and temporary storage 

 apart of the watercress required for market seems possible. It 

 is conceivable that sterilizing, with chlorine or other agent, the 

 beds where shellfish spat or young watercress is present might 

 have an injurious effect on the young growth, therefore that 

 treating the adult product would be preferable. 



4. Sterilizing by Cooking. — Where this can be done thoroughly 

 it is effective, and the Commission found that cockles and 

 mussels can be so thoroughly boiled as to bring about the 

 destruction of pathogenic organisms without rendering the 

 mollusc itself uneatable. An incidence of typhoid at Glasgow 

 in 1903 was due to raw cockles ; those who had eaten cooked 

 mussels and clams escaped injury.^ The heating is very often 

 imperfectly done : thus a number of enteric cases in South 

 London two years ago were due to cockles which were stated 

 to have been boiled for three minutes, but this had not sterilized 

 the interior. I have also quoted earlier an instance at Southend 

 (p. 171). When, as is frequently the practice, cockles are put 

 into the boiler in a bag, the centre portions may easily fail to 

 reach the temperature, a little above 60° C, necessary to 

 sterilize B. typhosus; hence it is better to put them in loose or 

 on a grating, and stir at first. The adoption of precautions 

 without injury to the trade is exemplified in Dr. Nash's report 

 to the Borough of Southend for 1904, in which he states that 

 the shellfish are now drawn from purer sources, and that 

 nearly every seller in the town subjects them to the action of 

 live steam under pressure for four or five minutes, the result 

 being that not a single case of typhoid due to cockles occurred 

 during the year.^ 



5. Sterilization by the Consumer, the last line of defence. — I 

 have suggested how this has been done instinctively, with a 

 measure of success, in the usual consumption of vinegar with 

 these foods, and have indicated how it may be more certainly 



^ Journ. R. San. Inst., vol. xxv,. part iii., 1904, p. 467. 



^ Local vigilance is, however, maintained, and I notice that at Southend on 

 Nov. 8, 1904, a fisherman was fined for selling mussels unfit for food. Dr. Klein 

 stated that 80 per cent, of these mussels contained a very large quantity of 

 sewage organisms, and the water from the spots at which they were taken was 

 polluted.— Public Health, Jan., 1905, p. 266. 



