vii INFECTION OF ANIMALS WITH PLAGUE 199 



late this latter. But what I wish to insist on is, that such 

 an occurrence is not likely under natural conditions to be 

 anything but exceptional ; there is no direct evidence that 

 this has happened, and in cases where it might have been 

 expected to happen — e.g. in many experiments recorded 

 by me — it certainly did not do so. 



As already mentioned, Hankin (I.e.) does not favour 

 direct transmission of plague by fleas. He regards the 

 flea as a true host, a living body in which the B. pestis 

 multiplies and in which it acquires virulence, believing, it 

 would seem, that not until these further phases have been 

 accomplished is the flea capable of transmitting plague to 

 a new individual (rat or man). From what I have already 

 said in this chapter it is, however, clear that definite 

 support of proof for this view of Hankin's has yet to be 

 furnished. 



