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392 C. GORDON HEWITT. 



near the points found to be most insanitary. He shows, as 

 English investigators have also shown, how the curves of 

 fatal cases correspond with the temperature curves and with 

 the curves of the activity and prevalence of flies which were 

 obtained by actual counts. He also adduced bacteriological 



J O 



evidence, and it is stated that one fly was found to be carrying 

 over one hundred thousand faecal bacteria. 



Bacteriological evidence. In addition to the evidence 

 of Jackson, to which reference has been made, further proof 

 that flies are able to carry the typhoid bacillus has been 

 available for some years. Celli (1 888) recovered the Bacillus 

 typhi abdominalis from the dejections of flies which had 

 been fed on cultures of the same, and he was able to prove 

 that they passed through the alimentary tract in a virulent 

 state by subsequent inoculation experiments. Ficker (1903) 

 found that when flies were fed upon typhoid cultures they 

 could contaminate objects upon which they rested. The 

 typhoid bacilli were present in the head and on the wings 

 and legs of the fly five days after feeding, and in the alimen- 

 tary tract nine days after. Firth and Hor rocks (1902), in 

 their experiments, took a small dish containing a rich emul- 

 sion in sugar made from a twenty-four-hour agar slope of 

 Bacillus typhosus recently obtained from an enteric stool 

 and rubbed up with fine soil. This was introduced with some 

 infected honey into a cage of flies together with sterile litmus 

 agar plates and dishes containing sterile broth, which were 

 placed at a short distance from the infected soil and honey. 

 Flies were seen to settle on the infected matter and on the 

 agar and broth. The agar plates and broth were removed 

 after a few days, and after incubation at 37 C. for twenty- 

 four hours colonies of Bacillus typhosus were found on 

 the agar plates and the bacillus was recovered from the 

 broth. In a further experiment the infected material was 

 dusted over with fine earth to represent superficially buried 

 dejecta, and the bacillus was isolated from agar plates upon 

 which the flies had subsequently walked, as in the former 

 experiment. They also found the bacillus 011 the heads, wings, 



