I06 DISTRIBUTION OF BACTERIA 



TABLE 15. Shoiuiug the results of cultures made from the 

 remaijis of syrup and milk ou which blow-flies infected with 

 B. pyocyaneus and B. prodigiosus had been allozved to feed 

 tJirougJi perforated zinc trays. 



Infection with B. pyocyaneus Infection with B. prodigiosus 



23 

 24 



4- { I colony) 



4- (i colon)) 



29 ,, o o + o 



30 ,, o o o o 



31 ,, o o -t- (i colony) o 

 33 ,, o o o o 



These experiments show that blow-flies infected with non- 

 spore bearing micro-organisms are capable of seriously con- 

 taminating both syrup and milk for at least a week by feeding 

 on them. Blow-flies originally fed on an emulsion oi B. pyocyaneus 

 constantly produced some degree of infection in both s}-rup and 

 milk for 16 days, and at even later periods occasional colonies 

 of B. pyocyaneus could be cultivated from their food. Milk was 

 apparently not infected after the 26th day, or syrup after the 

 28th day. Blow-flies which had been fed on B. prodigiosus 



