EXPLANATION OF DIAGRAM IV. 
Each red dot represents a case of typhoid fever. 
A — Farm where original case occurred in September and was 
nursed by wife of farmer B. 
B — Dairy farm where wife nursed preceding case and prepared 
the milk for market. She and one son were ailing for some days but 
did not stop work until October 8. 
The dash-lines represent the course and distribution of the milk 
from farm B. All the cases of typhoid were on this milk route. 
C and D were farms selling milk to farmer B. Xo typhoid oc- 
curred on these 2 farms. 
E — Farm receiving a small amount of milk daily from B for use of 
girl staying at farm. This girl contracted typhoid. 
F, G, and H — The 3 other dairy farms supplying milk to Elkton. 
The solid lines represent their routes. Xo case of typhoid on these 
routes. 
Population of Elkton 2, 542 
Total cases 64 
Houses invaded 39 
Invaded houses using B’s milk 39 
Invaded houses using well water 18 
Invaded houses using town water 21 
The large square — “ TOWX ” — represents the town of Elkton. 
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