191 Ij The Ottawa Naturalist. 219 



resources of the human race." All who have followed the 

 recent progress of the war against those diseases which have 

 kept the tropics closed to civiHzation will perceive the truth of 

 Lord Robson's statement. In Canada, however, we have not 

 these dread diseases, but we have others serious enough. It is 

 to one onlv that reference will be made as it is one in 

 which the naturalist is concerned. Next to tuberculosis the most 

 serious of the preventable diseases is infantile diarrhoea. This 

 disease is responsible for a greater mortality among infants than 

 anv other preventable disease, and the importance therefore of 

 its prevention is apparent. The high rate of mortality among 

 children in Canada may be realized from the fact that for the 

 four years 1904-7 the average infantile mortality per 1 ,000 births 

 in Ontario was 149.53, compared with 130.75 in England and 

 Wales, where there is a far greater and more congested population. 

 The greatest factor responsible for the spread of this disease is the 

 house-fly. In my address before this Society twelve months ago 

 I considered at length the relation of house-flies to public health 

 and the means of controlling these insects. In consequence, I 

 shall refer but briefly to this subject which illustrates the bearing 

 entomological knowledge has upon this aspect of public health. 

 Careftil investigations by Niven and others have shown that 

 there is a close correspondence between the aggregate number 

 of house-flies in houses and the aggregate number of deaths from 

 diarrhoea week by week and that there is a closer correspondence 

 of diarrhoeal mortality with the number of flies than with any 

 other varying seasonal fact, and that these seasonal facts are 

 capable of interpretation in the number of house-flies. Observa- 

 tions also have shown that flies cluster especially about the 

 noses and mouths of infants suffering from diarrhoea, and their 

 predilection for milk and sugar is well-known. Even though the 

 specific cause of this disease which carries off the lives of thou- 

 sands of infants in Canada each year is not known, it is enough 

 to know that the house fly is the chief agent in the dissemination 

 of the disease. Milk is also a factor in the spread of the disease 

 and the infection of the milk with the disease germs is largely 

 due to the agency of flies, as it has been shown that the bacterial 

 infection of milk can be reduced about 50% by protecting it 

 from flies. The relation of flies to typhoid fever is now becoming 

 an accepted fact and the house-fly is regarded as one of the most 

 serious menaces to the health of the civilized communities; its 

 aboHtion and control is rightly coming to be considered a neces- 

 sary step in the improvement of the sanitary conditions of our 

 cities and towns. Legislation is needed to prevent the exposing 

 of fruit, confectionery and other food supplies to the contact of 

 flies; to ensure that they cannot breed in the usual breeding 



