INSECTS AND PLAGUE. 67 



of dissemination, whereas the injection of the or- 

 ganisms through the proboscis is one of inocula- 

 tion. The flea appears not to undergo a gen- 

 eralized infection with the plague bacillus. 



It is possible that rats may become infected 

 with plague also by the eating of fleas which con- 

 tain bacilli,, although this has not yet been demon- 

 strated. Experimentally the disease has been pro- 

 duced in rats by feeding them infected tissues or 

 cultures. 



Verjbitski also found that the bedbug behaves in The Bedim*. 

 a manner exactly similar to the flea in the case of 

 plague. In actual epidemics, however, it seems 

 probable that this insect would be concerned only 

 in the transmission of the disease from man to 

 man, and not from rat to man. 



With the exception of the last paragraph the 

 above concerns the mere dissemination of micro- 

 organisms by insects. As noted, the diseases con- 

 cerned are bacterial in nature rather than proto- 

 zoan. Pathogenic protozoa may be excreted by in- 

 sects, but, if so, the event appears to be without 

 practical significance, either because the organisms 

 are not viable when excreted, or are not in a stage 

 of development to render them infective, or, what 

 is more probable, that they find no infection 

 atrium when in this condition. Those protozoa 

 which are transmitted by insects usually require 

 actual inoculation in order that they may cause 

 infection. 



B. Transmission 



Our knowledge is by no means complete on 

 the subject of insect transmission, as a whole, al- 

 though the essential facts have been worked out 

 in a number of instances, as in Texas fever, some 



