270 
CHARLES F. DAWSON. 
which lives at the expense of the red blood-cells, finally destroy¬ 
ing them. 
In a paper entitled “The Etiology of Yellow Fever,” read 
before the Pan-American Medical Congress in Havana, Cuba, 
February 4-7, 1901, Drs. Reed, Carroll and Agramonte, sur¬ 
geons U. S. A., show quite conclusively that yellow fever is an 
insect-borne disease. While they were able to produce it, by 
subjecting willing patients to the bites of the mosquito (culex 
fasciatus ), they failed to discover the identity of the causative 
organism. They conclude that B. icteroides of Sanarelli stands 
in no causative relation to the disease, but merely fills the role 
of a secondary invader. That mosquitoes serve as the inter¬ 
mediate host of the parasite of yellow fever, and are absolutely 
necessary for the ordinary spread of that disease. However, the 
disease may be produced experimentally by the inoculation of 
blood from an infected person. That a house may be said to be 
infected, only when there are present in it mosquitoes which have 
bitten persons suffering from the disease, and that the disinfec¬ 
tion of clothing, bedding and merchandise supposedly contami¬ 
nated by contact with the disease, is unnecessary. These observa¬ 
tions are of immense scientific and economic importance. They 
agree closely with the facts, as we now know them, thanks to the 
brilliant researches of Theobald Smith, concerning the etiology 
of Texas cattle fever. Possibly, in the near future, it will be 
shown that, as in Texas fever, the parasite of yellow fever is 
either a protozoan and, therefore, at present, uncultivatable by 
our primitive methods, or that it is a bacterium having such 
strict parasitic characters that it cannot be cultivated artificially ; 
or that it is, like the organism of bovine contagious pleuro¬ 
pneumonia, invisible because of its extreme minute¬ 
ness. 
In order to show that disease agents may be carried by in¬ 
sects to the animal kingdom, and especially by flies, I captured 
one with a pair of sterilized forceps from the exposed abdominal 
viscera of an experimental guinea-pig which had died of symp¬ 
tomatic anthrax. The fly was placed under the skin of a healthy 
