1 66 SUMMER DIARRHtEA 



The resiilts of the ciiltiiral exaviiiiations of flies. 



"The results of these examinations are considered under three headings : (ij the 

 distribution in flies from different localities of lactose fermenting and non-lactose 

 fermenting bacilli ; (2) the distribution of varieties of bacilli which do not ferment 

 lactose and do not liquefy gelatin in flies from different localities, and (3) the relative 

 frequency of the occurrence of such varieties in flies and in the excreta of children." 



(l) TJie distribution iti flies from different loealities of 

 lactose fermenting and non-hictose fermenting bacilli. 



Out of the 642 flies from diarrhcea infected houses examined, 209 (32 "/n) were 

 infected with bacilli which do not ferment lactose or liquefy gelatin, 283 (44 "/o) with 

 lactose fermenting bacilli of the colon type, and 43 (7''/o) vvith non-lactose fermenting 

 bacilli which liquefy gelatin. Of the 600 flies examined from non-diarrhoea infected 

 houses, 125 (20 "/o) contained bacilli which do not ferment lactose or liquefy gelatin, 

 212 (35 "/o) bacilli of the colon type, and 9 (i"6"/q) non-lactose fermenting bacilli 

 which liquefy gelatin. From these figures it can be seen that all three classes 

 of bacilli are more often found in flies from diarrhcea infected houses. 



" Further analysis of the results shows that during the whole period (July [4th to 

 October i6th) covered by these examinations at least 20 "/o of flies from all sources 

 were infected with colon bacilli. The degree of infection with both colon bacilli and 

 non-lactose fermenters was greatest during August and the first three weeks of 

 September. In the series of flies from diarrhoea infected houses the greatest degree of 

 infection with non-lactose fermenters (51 **/o) was reached in the third week in August. 

 After the second week in September very few of the flies were found to be infected. 



"It is of interest and importance to note that the percentage of infection in flies 

 of separate batches obtained from one place on different occasions varied greatly. 

 For example, from one non-diarrhoea infected house (Series G) 1 1 batches of flies were 

 obtained. On two occasions only 5 o/^, were infected with non-lactose fermenting 

 bacilli, while on three occasions nearly 40 "/o were infected. Of the whole series 

 24 "/o were infected. In the same series the infection with colon bacilli varied from 

 25"/^ to 780/g (mean 44*Vo)- The degree of infection with non-lactose fermenting 

 bacilli in batches of flies (Series C) obtained from the diarrhoea infected farm house 

 near Cambridge varied from 5 "/o to 69%, with colon bacilli from 50 "/o to 93 %■ 



" Similar variations were seen in batches from different diarrhrea infected houses in 

 Birmingham (Series A). In this series the infection with non-lactose fermenting 

 bacilli varied from 0% to 86 "/o, and with colon bacilli from 0% to 87 "/o. 



" According to the writer's observations a high degree of infection with non-lactose 

 fermenting bacilli cannot be inferred from a high degree of infection with colon 

 bacilli." 



(2) The distribution of varieties of bacilli which do not ferment 

 lactose or liquefy gelatifi in flies from different localities. 



In Table 21 the varieties of non-lactose fermenting bacilli which occurred in the 

 flies of the different series are recorded. In many cases the percentage of flies infected 

 is given. 



