298 THE CARRIAGE OF VARIOUS MICRO-ORGANISMS 



The morphological characters and cultural reactions of 123 

 strains of bacteria were examined by the authors. Among those 

 identified were two Streptococci and several Staphylococci and 

 Sarcinae. One hundred and six were small gram-negative non- 

 spore-bearing bacilli ; these were grouped as follows : 



Chromogenic group : two sti'ains of B. pgocyaneus were 

 isolated from flies from a knackers' yard. 



Colon group : 41 colonies of this group were picked off 

 haphazard and classified according to McConkey as follows : 

 B. acicli lactici type ... 19'5 percent. 



B. coll communis type ... 122 ,, „ 

 B. neapolitanus type ... 19'5 „ ,, 



B. lactis aerogenes type ... 46'4 „ 

 Salmonella group: one bacillus gave identical reactions 

 to B. enteritidis Gaertner, except that the serological tests 

 were negative. 



Morgans Infantile Diarrhoea group : one identical to 

 Morgan's No. 1, and many others closely resembling it and 

 Morgan's Nos. 2 and 3 were obtained. 



Others were included in the proteolytic, acid lactose- 

 sucrose (saccharose), and miscellaneous groups. 

 The authors conclude : " It is clear that flies from the suburbs 

 where infantile diarrhoea is rare carry far less bacteria than those 

 in the city where it is common. It was, nevertheless, impossible 

 in the time at our disposal to correlate exactly the number or 

 varieties of bacteria carried by flies in the city with the number 

 of cases and deaths from infantile diarrhoea in individual sti'eets. 



" As the amount of dirt carried by flies in an}' particular 

 locality, measured in terms of bacteria, bears a definite relation to 

 the habits of the people and the state of the streets it demon- 

 strates the necessity of efficient municipal and domestic cleanliness 

 if the food of the inhabitants is to escape pollution, not only with 

 harmless but also with occasional pathogenic bacteria." 



In his study of the micro-organisms carried by flies under 

 normal conditions to which reference has already been made 

 (p. 245), Graham-Smith found that more than one-third of all 

 the flies examined were infected with lactose-fermenting bacilli of 

 the colon type. 



