174 



XIII. APPENDIX A. 



FURTHER OBSERVATIONS ON THE DISSEMINA- 

 TION OF BACTERIAL AND OTHER ORGANISMS 

 BY MUSCA DOMEST1CA. 



I. THE RELATION OF FLIES TO SUMMER DIARRHCEA OF 

 INFANTS. 



Nash, was one of the first medical observers to call 

 attention (in 1902) to the remarkable coincidence between 

 the abundance of flies and the prevalence of this serious 

 infantile disease. In the years 1902 and 1903 the summers 

 were wet and therefore unfavourable to the breeding and 

 activity of M . domestica, and in these years the diarrhceal 

 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 

 responsible for the spread of this disease and supported his 

 contention with a further instance, namely, that " in the 

 early part of September, 1902, flies became prevalent, and 

 co-incidentally diarrhoea, which had hitherto been conspi- 

 cuous 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 admir- 

 able breeding place for this insect. He has shown the actual 



