THE DANGER OF FLIES 727 



epidemic diarrhoea. He points out that the prevalence of 

 diarrhoea follows the earth's temperature, and does not follow 

 the temperature of the atmosphere. It is a well-known fact that 

 this illness is more prevalent in the houses of the poor than in 

 the mansions of the rich. As Dr. Newsholm, Medical Officer of 

 Health for Brighton, said : " The sugar used in sweetening milk 

 is often black with flies which have come from neighbouring 

 dust-bins or manure heaps ; often from the liquid stools of 

 diarrhoea patients in the neighbouring houses. Flies have to be 

 picked out of the half-emptied can of condensed milk before 

 it can be used for the next meal. When we remember the 

 personal uncleanliness of some mothers and that they often 

 prepare their infants' food with unwashed hands, the inoculation 

 of this food with virulent colon bacilli of human origin ceases to 

 be a matter of surprise." 



Compared with cow's milk, which nourishes a very numerous 

 progeny of bacteria, the bacterial content of Nestle's milk is 

 very low, according to Dr. Sandilands. In certain seasons the 

 cow's milk is exposed to temperatures which favour an enormous 

 multiplication of bacteria, and 3'et it is not then a frequent 

 source of diarrhoea, in fact mere numbers have little or no 

 influence on the incidence of the illness. The greater number 

 of cases are due to infection conveyed from some patient in the 

 near neighbourhood and conveyed mechanically by flies. 



The great attraction of the sweetened condensed milk for 

 flies to some extent explains the greater prevalence of infantile 

 diarrhoea among children fed on this preparation. 



As was stated above, one of the most remarkable features in 

 the prevalence of infantile diarrhoea is that it follows the rise 

 and fall of the earth's temperature, and not that of the air. In 

 the same way the number of house-flies does not reach its 

 maximum with the first burst of hot weather. The prevalence 

 of these insects follows rather than coincides with periods of 

 great heat. The flies, in fact, lag behind the air temperature 

 and persist for a time after the hot weather has ceased. In 

 other words, the meteorological conditions associated with an 

 increase or a diminution of the prevalence of diarrhoea exercise 

 a similar influence on the prevalence of flies. 



The transference of the Filaria bancrofti, whose presence in 

 the human body in the adult stage is associated with various 

 diseases of the lymphatics, the most pronounced of which is the 



