CARRIAGE OF DISEASE 125 



Exact Proof 



From the laboratory point of view, a number of ex- 

 act experiments have been made, and we quote the fol- 

 lowing paragraphs from Nuttall and Jepson : 



''Celli (1888) fed flies with pure cultures of the 

 Bacillus typhosus and examined their contents and de- 

 jections microscopically and culturally. Inoculations 

 on animals were also made, proving, as he supposed, 

 that the bacilli which passed through flies were viru- 

 lent. (He made similar observations with the Spiril- 

 lum Finkler-Prior.) 



''As Ficker (1903, p. 274) properly points out, 

 Celli's statement has less value to-day, since at the time 

 he carried out his experiments no suitable means ex- 

 isted for properly differentiating B. typhosus from 

 other organisms of similar character. 



"Firth and Horrocks (1902) kept M. domestica 

 (also blue-bottles) in a large box measuring four by 

 three feet, with one side made of glass. They were 

 fed on material contaminated with cultures of B. 

 typhosus. Agar plates, litmus, glucose broth, and a 

 sheet of clean paper were at the same time exposed in 

 the box. After a few days the plates and broth were 

 removed and incubated with a positive result. The 

 flies' excreta on the paper yielded B. coli almost in pure 

 culture. In a second experiment some fresh typhoid 

 stool to which a typhoid culture had been added was 

 dusted with earth and served as the infective material; 

 colonies of B. typhosus appeared on the plates. In a 



