358 ENTOMOLOGICAL NEWS. [Oct., ’o8 
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 Stomozxys, the stable fly, 
affords a good medium for transmission of Bacillus pestis. 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 Stomoxys 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 
