EPIDEMIOLOGICAL EVIDENCE 253 



years 1902 and 1903 the summers were wet and therefore un- 

 favourable to the breeding and activity of M. domestica, and in 

 these years the diarrhoeal diseases were less prevalent and the 

 infantile mortality rate was considerably below the average. He 

 suggested (1903), in a paper read before the Epidemiological 

 Society of London in January, 1903, that flies carried the infective 

 material from all kinds of filth to the food supplies and were re- 

 sponsible for the spread of this disease and supported his contention 

 with a further instance, namely, that " in the early part of Sep- 

 tember, 1902, flies became prevalent, and co-incidentally diarrhoea, 

 which had hitherto been conspicuous by its absence, caused 

 thirteen deaths in Southend. Then came a spell of cold weather ; 

 the flies rapidly diminished in number, and no further deaths from 

 diarrhoea were recorded " (1905). In 1904, by means of a " spot 

 map " he found that the great majority of deaths from diarrhoea 

 occurred in the proximity of brick fields in which were daily 

 deposited some thirty tons of house refuse, an admirable breeding 

 place for this insect. He has shown the actual danger which exists 

 in flies carrying bacterial organisms to milk as many other in- 

 vestigators have shown, and the danger resulting from the co- 

 incident occurrence of uncovered milk and infected flies is too 

 obvious to need emphasis. 



Newsholme (1903) discussed the possibility of food infection 

 by flies in the houses of the poor. He states : " The sugar used 

 in sweetening the milk is often black with flies which may have 

 come from a neighbouring dustbin or manure heap, or from the 

 liquid stools of a diarrhoeal patient in a neighbouring house. 

 Flies have to be picked out of the half-empty can of condensed 

 milk before its remaining contents can be used for the next meal." 

 The observations of Copeman (p. 241) have already been mentioned 

 and similar instances of the relation between flies and the incidence 

 of summer diaiThoea have been referred to by Snell (1906) and 

 other medical oflicers of health in their reports. Sandilands 

 (1906) states that there are "good grounds for the supposition 

 that in this disease, which in some respects is analogous to typhoid 

 fever and cholera, flies may be carrying agents of the first im- 

 portance." He observes that the meteorological conditions which 

 influence the prevalence of diarrhoea exercise a precisely similar 



