SUMMER DIARRHCEA I/I 



houses. Experiments previously quoted (p. 109) have demon- 

 strated that non-spore producing bacilH can survive for several 

 days in the intestines of flies, and that during that period the 

 flies can infect the materials on which they feed and on which 

 they settle. If the larvse are allowed to eat food contaminated 

 with Morgan's bacillus, this organism is sometimes present in 

 a small proportion of the flies which eventually emerge from 

 them (p. 121). 



Similar investigations, which will be published in the Report 

 of the Medical Officer to the Local Government Board, were 

 carried on by the writer during the summer of 191 2, which was 

 unusually cold and wet. Very few cases of summer diarrhea 

 occurred either in Cambridge or in Birmingham, and flies were 

 difficult to obtain. Though non-lactose fermenting bacilli of 

 various kinds and bacilli of the colon type were isolated from the 

 flies, not a single example of the Morgan type was met with. In 

 regard to the presence of Morgan's bacillus in flies obtained from 

 these two towns the contrast between the severe diarrhoea year, 

 191 1, and the non-diarrhoea year, 1912, is very striking and 

 suggestive. 



Morgan and Ledingham (1909, p. 142) examined batches of 

 flies from diarrhoea infected and non-infected houses, and obtained 

 Morgan's bacillus from nine (25 "/(,) out of 36 batches from infected 

 and from one (3 %) out of 32 batches from non-infected houses. 



Nicoll (x, 191 1) found that certain varieties of bacilli "seem 

 to be able to establish themselves in the fly's intestine, to the 

 exclusion sometimes of other forms, and to remain there for 

 a considerable time. Amongst these may be mentioned Morgan's 

 bacillus No. i." Orr (1911, p. 380) isolated non-lactose fer- 

 menting bacilli from 16 out of 74 batches of flies. Morgan's 

 bacillus was found twice. 



Before the exact part played by flies in the dissemination of 

 Morgan's bacillus can be finally decided the sources from which 

 they obtain the infection must be demonstrated. Up to the 

 present very little information on the possible sources of infection 

 has been obtained. In certain outbreaks the organism is present 

 in the excreta of a large proportion of children suffering from 

 epidemic diarrhoea, and no doubt flies which can settle on such 



