172 SUMMER DIARRHCEA 



material become infected. Morgan and Ledingham (1909, p. 142) 

 isolated Morgan's bacillus once from fresh cows' faeces (18 animals 

 examined) but not from the faeces of the horse (13 animals 

 examined). Lewis (191 2) isolated this bacillus from the faeces 

 of five out of twenty healthy mice. Possibly more extended 

 observations will reveal that this type of bacillus is commonly 

 present in certain materials which attract flies and to which they 

 have access. It must be remembered however that all organisms 

 giving the cultural reactions of Morgan's bacillus do not 

 necessarily belong to one species since Lewis (19 12, p. 276) has 

 shown that bacilli of this type maj^ be separated into groups by 

 means of agglutination tests. 



Summary. 



Recent epidemiological investigations strongly suggest that 

 house-flies play a not unimportant part in the dissemination of 

 summer diarrhoea. More extended observations on the corre- 

 spondence between the numbers of flies and the numbers of 

 cases of diarrhoea occurring in several districts, and on the 

 effects of exterminating flies in limited areas, ma)' aid in deciding 

 the exact part played by flies. 



The bacteriological investigations made up to the present 

 show that flies can obtain and carry in their intestines most of the 

 bacteria of the non-lactose fermenting types found in the faeces 

 of children suffering from summer diarrhcea, and probably infect 

 articles of food with them. Whether Morgan's bacillus is a 

 causative agent in this disease or not, the facts relating to its 

 presence in flies well illustrate the powers of these insects of 

 acquiring and carrying organisms of this type, for in outbreaks 

 associated with the presence of Morgan's bacillus in the stools of 

 infants this bacillus is often found in flies caught in houses in 

 which cases have occurred, but it is rarely present in flies from 

 other situations. 



The epidemiological and bacteriological evidence is so 

 suggestive, and the disease is of such importance, that an 

 attempt to definitely settle the connection between flies and 

 sunnner diarrhoea by preventive measures against flies in a 

 selected area seems now justifiable. 



