148 FOOD-POISONING 



" These experiments show that B. enteritidis may be present 

 in the contents of the crops and intestines of flies for a least 

 7 days after infection. Flies can infect plates over which they 

 walk for some days in spite of the fact that the organism can 

 seldom be isolated from their legs (once in 32 cultures). When 

 walking over plates flies constantly place their proboscides on 

 the medium and in most cases leave imprints on its surface. 

 The colonies develop round these marks. The infection of the 

 plate is therefore probably due, in large measure, to inoculation 

 by the fly's proboscis. 



" It is not improbable that by means of more careful and 

 extensive experiments B. enteritidis might be isolated for even 

 longer periods, since several of the plates in this series gave 

 negative results owing to being overgrown by B. coli-\\\s.& 

 organism." 



Faichnie's (1909) experiments on breeding larvae in the feeces 

 of a man suffering from paratyphoid fever {B. paratypJiosus A) 

 and similar experiments with cultivated strains have already 

 been quoted (p. 115). 



Torrey (191 2) isolated B. paratypJiosus A from three cultures 

 from ' wild ' flies caught in New York. He employed agglu- 

 tination and absorption tests with sera made from stock cultures 

 in identifying these organisms. " Inoculations into guinea-pigs 

 of these fly paratyphoid cultures disclosed approximately the 

 same degree of toxicity as the stock paratyphoid cultures. 

 Feeding experiments with white mice resulted negatively." 

 Nicoll (191 1, p. 383) isolated B. paratypJiosus B from two flies, 

 " from the external surface and intestine of one fly and from the 

 intestine of the second. The identity of the bacillus was 

 confirmed by Dr F. A. Bainbridge." 



The observations which have been quoted show that flies, if 

 suitable opportunities of visiting infected material occur, may 

 carry and distribute organisms of this type for several days. No 

 instances of infection by flies have yet been recorded. In the 

 identification of these bacilli serological tests are necessary, since 

 allied organisms frequently occur in the intestine of the fly. 



