EXPLANATION OF DIAGRAM III. 
J H, RBN, ETT, OH, J M B, and C F J are the farmers pro- 
ducing milk. 
A is the milk dealer delivering milk in both Milton and Dorchester. 
B is the milk dealer delivering milk in Hyde Park. 
The lines connecting the producing farms and the milk dealers 
show to which dairy the farmer sold his milk. 
The large squares represent Milton, Dorchester, and Hyde Park. 
The dash-lines extending from AtoB into the towns represent the 
milk routes carrying the supposedly infectious milk. 
Each dot represents a case of diphtheria and is placed on the 
milk route from which it was supplied. 
C, D, E, F, G, and H represent the other dairies selling milk. The 
lines extending from them into the towns represent their routes and 
are inserted to show their freedom from diphtheria cases. 
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