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38o INVESTIGATION, ETC., OF MILK-BORNE EPIDEMICS 

 " Or taken together : — 



Eatio of attacks 

 to houses. 



56 houses were supplied . . . .1 ^^^^_ 



31 were attacked . . . . .j-'-^''^ 



114 cases resulted, or more than 2 cases per house. 



The inmates of these houses numbered 453, so that 25-1 per cent, 

 were attacked, or just a quarter of the whole number, 



" 2. Milkman Y started with a pure supply from Ashton in the 

 county of Somerset, but at Bower Ashton he met the X cart and 

 occasionally took a supplementary supply from the churn consigned 

 to Clifton ; after receiving which he supplied milk, yielding two 

 cases of typhoid, at Bower Ashton, proceeded to Leigh Woods, 

 where six more cases appeared in three houses supplied, and then 

 entered Clifton. 



" On his rounds in Clifton : — 



Batio of attacks 

 to houses. 



40 houses were supplied , . . . \ 



18 were attacked |45-o per cent. 



48 cases resulted, or more than i case per house. 



The inmates of these houses numbered 308, so that 15-5 per cent, 

 were attacked, or about one-sixth. 



" 3. The third and last supply known to be implicated (Z) came 

 from a farm at Westbury, and entered the city from the north, at 

 a point remote from the Suspension Bridge over which supplies X 

 and Y came. The milk from this farm is distributed in Clifton on 

 three rounds. Two of these rounds were entirely innocent of cases, 

 and the third round was (with one exception, a servant who lived 

 close to, and admits to frequently obtaining casual supplies from 

 the branch dairy to which unused X milk was returned) also inno- 

 cent of cases up to a certain point, but beyond this point cases 

 began to occur with marked frequency (see diagram). 



" On comparing the routes of the three dairymen, which we had 

 plotted upon a map, it was at once discovered that, at the very 

 corner where this change from freedom to infection occurred, Z's 

 round met that of the X supply, in charge of the man B ; and Z 

 admitted that he was in the habit, when running short, of obtain- 

 ing at this point supplementary supplies from B. After this, 

 cases commenced at the very next house he supplied, and con- 

 tinued with considerable frequency along his route : — 



Ratio of attacks 

 to houses. 



Before adding the X mi,k{-| S^-faZclir'"'!} 9° per cent. 

 I case resulted (obtaining casual supplies from X shop). 



Ar^ J J- ^1- V -11 ri6 houses were supplied! , . 



After adding the X milk .| g ^^^^ attacked .J 5°*° P^"^ ^^"^^ 



22 cases resulted. 



