DETECTION OF MILK EPIDEMICS. I2/ 



milk dealers, is quite impracticable in large cities. In a large 

 city, like New York or Boston, the milk is drawn from a 

 very wide territory, and is more or less mixed before it 

 reaches the consumer. Moreover, the large milk distributors 

 in such cities draw milk from so many different sources that 

 it rarely occurs that the same consumer will receive milk for 

 any considerable length of time from the same source and it 

 is, therefore, quite impossible to trace a milk epidemic to a 

 given milk supply. Indeed, up to the present, no such milk 

 epidemic has been traced to the general milk supply in large 

 cities. It is quite probable indeed almost certain that, in 

 the large communities, a part of the typhoid, scarlet fever 

 and diphtheria may be due to milk infection; but the wide 

 distribution of milk through the city will make it rare that 

 such a localized milk epidemic should occur as is found in 

 small communities, where a given milkman day after day 

 supplies the same set of customers with milk from his own 

 farm. In this respect, therefore, the milk supply of the 

 larger city is probably more reliable than that of the smaller 

 community. If the milk of a given farm becomes impreg- 

 nated with pathogenic bacteria this will be likely to occur 

 for a number of days. There is, therefore, a much greater 

 chance of infection where the same customers day after day 

 receive the milk than where the milk from any farm is 

 poured into a general supply, more or less mixed with that 

 from other farms and then distributed, a little of it to one set 

 of customers on one day and to another set on another day. 

 The intensity of the infection in a large city is slight, 

 although the possibility of infection extends over a wider 

 circle of customers. In the small community the intensity of 

 the infection is great, although the number of people affected 

 is comparatively small. 



The detection of the source of such a milk epidemic is 

 useful in two ways. In the first place, it is a means of satis- 

 faction to the community to know the source of the infec- 



