88 THE FLEA [CH. 



stomachs bacilli identical with B. pestis. He suggested 

 that the bacillus was carried from rats to men ; and 

 he brought forward some evidence tending to show 

 that infected fleas could transmit infection by biting. 

 But Simond was not able to bring forward conclusive 

 proof. He pointed out a line of research to others 

 which has proved exceedingly fruitful. In the same 

 year (1898) Hankin suggested that some biting insect 

 might be the means of transmission from rats to man. 

 The bacillus of plague has now been identified in 

 ants, bugs, and flies as well as fleas. It seems likely 

 that any suctorial insect which feeds on a plague- 

 stricken rat will take numbers of the bacilli into its 

 stomach. 



The points which Simond wished to establish were 

 that plague-stricken rats with fleas are exceedingly 

 infective, that they cease to be infective when they 

 have been deserted by their fleas, and that fleas which 

 infest rats will transfer themselves to man. Since 

 1905 an elaborate series of observations and experi- 

 ments have been carried out. Post-mortems have 

 been made of countless rats. Numberless fleas have 

 been collected and dissected. But this summary 

 would be very incomplete if it did not mention the 

 work of Verjbitski, a Russian doctor at Cronstadt, 

 whose labours remained almost unnoticed although 

 he made his experiments as long ago as 1902-1903. 

 His thesis, written in Russian, was not published in 



