35 8 ENTOMOLOGICAL NEWS. [Oct. , '08 



mission from rat to man is due essentially to the introduction of 

 the intestinal evacuations into the bite of the flea. It is the 

 "rubbing it in" which is significant. 



In the first experiments performed by the British Indian 

 Plague Commission a technical oversight was suffered in their 

 premature conclusions concerning the infectivity of the sali- 

 vary glands. In this instance the investigators neglected to 

 provide control measures. A bacteriological determination of 

 the natural flora of the healthy flea's salivary glands should 

 have been first obtained. I have isolated from the body cavity 

 of this insect in the normal state numerous bipolar rod organ- 

 isms resembling the plague bacilli. 



Experimentally an insect like the Stom o.vys, the stable fly, 

 affords a good medium for transmission of Bacillus pcstis. In 

 the laboratory one can inoculate the stable fly by feeding plague 

 cadaver. In this respect the flea is not a good subject, as it 

 seems to prefer starvation to feeding on cadaverous tissue. 

 By keeping the plague meat moist with sterile broth the fly 

 is able to subsist for six to ten days. An examination of the 

 proboscis and intestinal tracts of a fly thus nourished reveals 

 innumerable plague-like organisms, proving also culturally 

 positive. The Stomo.vys which commonly bites man could 

 transmit Bacillus pestis directly through the proboscis from 

 the salivary glands. The intestinal discharges would be vastly 

 greater in volume of bacterial content than even those of the 

 flea, which is reputed to evacuate ten to one hundred thousand 

 bacilli per cc. Consequently, the rubbing process in the case 

 of the fly would have to be reckoned with. The question arises 

 in what environment, in nature, would the flies be exposed to 

 contamination by plague. We know that rats devour each 

 other ; that the weak and sick are at all times exposed to the 

 attacks of the stronger. Thompson, Journal of Hygiene (1906, 

 Vol. vi., 550) makes the statement that in Bombay at the 

 Plague Laboratory more than eight per cent, of the rat car- 

 cases brought in had been devoured by their fellows, and 

 sometimes so completely that nothing but head, paws, tail and 

 skin remained. The cadavers of plague rats, as we have seen 

 in San Francisco, are soon torn open, and the viscera exposed. 

 Many of these have been found in harbor front stables covered 

 with flies. The stable fly will feed on the plague tissue thus 



