DETECTION OF MILK EPIDEMICS. 



125 



when the relation of the milk of the three milkmen was 

 examined and tabulated by the graphic method shown in the 

 figure, it became evident that it was only one of these three 

 sources of milk that caused the infection. As can be seen 



s 



FIG. 23. 



li 



Graphic representation of a milk epidemic of scarlet fever. A, B and C are milk pro- 

 ducers, i and 2 are milk distributors. The circles represent households, the inclosed dots 

 cases of scarlet fever. Upon farm A there was a case of scarlet fever. The diagram shows 

 that milk from farm A gave rise to scarlet fever even when mixed with other milk. 



from the diagram the milk from the farm in question (shown 

 by the large circle A), not only produced cases of scarlet 

 fever where it was distributed directly from the dealer A, 

 but it also gave rise to the disease in the routes of the other 

 two milkmen where it was mixed with their milk and dis- 

 tributed to their own customers. The figure shows con- 



