10 



bacteria would soon die from desiccation on the appendages 

 of the insect, and at any rate the number so conveyed is 

 small compared to those contained in its crop and intestine. 

 Carriage within is certainly more lasting, for Graham Smith 

 (1910), to whom we are indebted for the most thorough 

 investigation of this subject, isolated typhoid and other 

 bacilli from the intestinal contents of flies six days after 

 feeding on material containing the organism under test. 

 The faeces ceased to afford growths after two days when 

 typhoid bacilli were the infecting organism used, but with a 

 more robust organism, such as anthrax, which can protect 

 itself from the effects of drying, the time was much longer. 



TABLE I. Showing the Longest Period after which Organisms 

 ners Recovered from Flies Fed on Cultures. 



The accompanying table (Table I.), taken from Dr. 

 Graham Smith's report, summarises the result of his experi- 

 ments on the length of time during which various bacilli can 

 be recovered from the outside and inside of flies fed on 

 infected material. As the author is careful to point out, 

 gross infection was produced in these experiments by 

 feeding upon pure cultures, and they do not do more than 

 indicate the duration of life of various pathogenic bacteria 

 \mder favourable conditions. 



Bacot (1911), Ledingham (1911), and Graham Smith (1911) 

 have further shown that in the case of larvae fed on material 

 infected with various organisms JB. pyocyaneus, B. typhosus, 

 and B. anthracis respectively the infection may be carried 

 through the chrysalis stage and recovered from the contents 

 of the intestine of the fly after emergence. Fortunately, 



