MTIOLOGY 



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faeces or the urine, and can infect food and drink directly or in- 

 directly through the agency of flies, and by means of this infected 

 food or infected hands the bacilli can gain entrance into another 

 human host, and set up the infection anew. Of the foods and drinks 

 which are of importance, the first and most important is milk, while 

 water, shellfish, fish, and dried fish, may also be mentioned as of 

 great importance. Attacks have also been traced to ice, and, 

 indeed, no food or cooking utensil can be considered free from 

 possible infection. Of great importance in the tropics are un- 

 cooked green vegetables, which are grown in gardens often manured 

 by means of human excrement. Faecally polluted dust and fsecally 

 polluted clothes must also be assigned a prominent place in connec- 

 tion with the spread of the disease. 



With regard to the epidemicity of enteric fever, it will be clearly 

 understood that the basis of the epidemic as the basis of the endemic 

 is the carrier, but the characters of the epidemic will largely depend 

 upon the means by which the bacilli are introduced into the new 

 non-immune hosts. Often this is by flies; hence the name ' autum- 

 nal fever ' sometimes applied to the disease, because the local epi- 

 demic takes place after the time of their greatest prevalence. 

 Epidemics due to milk will be found to agree with the distribution 

 of this food by, generally, one dairy. The present writers once, 

 during an outbreak of enteric fever and dysentery in a tropical 

 town, bought by chance a sample of milk which, on investigation, 

 was found to contain the B. coli — a sure proof of human faecal 

 contamination, which might have arisen from watering the milk, 

 because water is often added by the seller to the milk oiBos indicus, 

 and this escapes the notice of the buyer, because the milk is much 

 richer than that oiBos taurus, and therefore does not appear to be 

 diluted. As the water may have come from some polluted source — 

 e.g., a well or a roadside drain — this is very dangerous. Epidemics 

 due to oysters and other shellfish will agree with the seasonal use 

 of these shellfish, and may even be traced to certain breeding- 

 grounds which may be situate near the mouth of a sewer, or in 

 which the oyster-bed itself has become infected with bacilli. 

 Another good instance of the cause of small epidemics is the tracing 

 of the infection by Hamer to the fried-fish shops so common in 

 London. But the infection of food materials will not give rise to 

 the sudden widespread epidemic which will arise if the water-supply 

 is contaminated. Maidstone, in 1896, had 35,000 inhabitants, of 

 whom 1,900 persons suffered from enteric fever during the months 

 of September, October, and November, due to contamination of the 

 town's water-supply. In the tropics polluted wells are a prevalent 

 cause of endemic and epidemic enteric fever. The present writers 

 were acquainted with a town in which so-called ' remittent,' really 

 typhoid, fever was very prevalent, and where in a certain area the 

 wells and the cesspits, which always contained water, were only 

 separated by a wall one brick thick. 



The bacilli do not live when dried ; still, it is probable that they 



