APPENDIX A 176 



examination from infected and uninfected houses in 

 Paddington and from a country house situated many miles 

 from London, where no cases of diarrhoea had occurred, at 

 any rate within a radius of two miles. The flies were killed 

 with ether vapour and crushed with a sterile rod in peptone 

 broth. The result was that Morgan's bacillus was isolated 

 from nine of the thirty-six batches from infected houses and 

 from one of the thirty-two batches from uninfected houses. 

 It was also got in five out of twenty-four batches from the 

 country house." Dr. Morgan in the course of a letter to 

 me says : " I certainly think they are carriers of summer 

 diarrhoea, and the variety I especially suspect of doing this 

 is the Musca domestica." 



Hamer in his first report (1908) points out a difficulty in 

 the way of accepting this relation of flies to summer diar- 

 rhoea. He states : " It should be pointed out that there are 

 certain difficulties in the way of accepting the thesis that 

 the correspondence exhibited in the curves [he refers to the 

 fly curve and diarrhoea curve] affords reason for concluding 

 that flies and summer diarrhoea stand to one another in 

 relation of cause and effect. At the commencement of the 

 hot summer weeks, when the number of flies has begun to 

 show marked increase, the diarrhoea curve is rapidly rising. 

 After some weeks the number of flies reaches the maximum, 

 and then diminishes, and so, in almost precise correspon- 

 dence, does the amount of diarrhoea. A period is later 

 reached, towards the close of the hot weeks, at which the 

 number of flies is still as markedly excessive as at the 

 earlier period when the amount of diarrhoea was increasing, 

 but at the later period the amount of diarrhoea is declining; 

 it even anticipates decline in the number of flieS. If the fly 

 is to be regarded as the carrier of the organism which 

 causes diarrhoea, it might perhaps have been anticipated that 

 at the later period the number of flies still being excessive 

 and infective material being then presumably more widely 



