17 



nor less, as has a Manchester millowner residing at St. Annes, 

 if the latter also harbours Bacillus typhosus. This attitude 

 has its significance : any person who is suffering from typhoid 

 fever is a focus of infection ; the service is a public one, and its 

 result has been the preservation of the health of the individual. 

 And so, because of the existence of medical research, no one 

 cause of dissemination of enteric has, for any great length of 

 time, been over-estimated in value by the public health 

 administration ; on the other hand fishery authorities have 

 rather tended to become obsessed with the idea that mussels 

 are the way in which typhoid is carried. It has been said that 

 there still remains a persistent residue of the disease and that the 

 cause is polluted shellfish, but in view of the now generally 

 recognised fact that apparently healthy persons may be 

 " typhoid carriers " this view cannot be maintained. 



The evidence that Enteric Fever is conveyed by Shellfish. 



Without doubt the consumption of sewage-infected oysters, 

 mussels and cockles is a cause of enteric fever, but a candid 

 survey of all the available evidence does not convince one 

 that this is even a prominent cause. It must be remembered 

 that the role of shellfish in conveying the infection has only 

 been attentively studied since 1894, when the late Dr. H. T. 

 Rulstrode made his well-known investigation into '"oyster cul- 

 ture in relation to disease." Further, administrative measures 

 designed to prevent communication of typhoid by this means 

 cannot have been effectively applied until the first few years 

 of the present century, yet a glance at the table on p. 15 will 

 show that an enormous decrease in the mortality from the 

 disease characterised the last decades of the 18's. For this 

 decrease we must therefore look to other action than that 

 taken with respect to polluted shellfish, and the same kinds of 

 action have doubtless continued to be taken, and with the same 

 success, during the last dozen years or more. The statistics 



