Dr. Lazear had been previously bitten by a contaminated insect without
after effects, he deliberately allowed this particular mosquito, which
had settled on the back of his hand, to remain until it had satisfied
its hunger.

On the evening of September 18, five days after the bite, Dr. Lazear
complained of feeling "out of sorts," and had a chill at 8 P.M.

On September 19, twelve o'clock noon, his temperature was 102.4 deg., pulse
112; his eyes were injected and his face suffused; at 3 P.M. temperature
was 103.4 deg., pulse 104; 6 P.M., temperature 103.8 deg. and pulse 106; albumin
appeared in the urine. Jaundice appeared on the third day. The
subsequent history of this case was one of progressive and fatal yellow
fever, the death of our much-lamented colleague having occurred on the
evening of September 25, 1900.

Evidently in this case the evidence is not satisfactory as to the fatal
attack being the result of the bite by a mosquito "while on a visit to
Las Animas Hospital," although Dr. Lazear himself was thoroughly
convinced that this was the direct cause of his attack.

The inference by Dr. Reed and his associates, from the experiments thus
far made, was that yellow fever may be; transmitted by mosquitoes of the
genus _Culex_, but that in order to convey the infection to a nonimmune
individual the insect must be kept for twelve days or longer after it
has filled itself with blood from a yellow fever patient in the earlier
stages of the disease. In other words, that a certain period of
incubation is required in the body of the insect before the germ reaches
its salivary glands, and consequently before it is able to inoculate any
individual with the germs of yellow fever. This inference, based upon
experimental data, received support from other observations, which have
been repeatedly made, with reference to the introduction and spread of
yellow fever in localities favorable to its propagation. When a case is
imported to one of our southern seaport cities, from Havana, Vera Cruz,
or some other endemic focus of the disease, an interval of two weeks or
more occurs before secondary cases are developed as a result of such
importation. In the light of our present knowledge this is readily
understood. A certain number of mosquitoes having filled themselves with
blood from this first case after an interval of twelve days or more bite
nonimmune individuals living in the vicinity, and these individuals
after a brief peri