cases the result was negative.  In considering the experimental evidence thus far obtained, the attention of the members of the board was attracted by the fact that in the nine inoculations with a negative result “the time elapsing between the biting of the mosquito and the inoculation of the healthy subject varied in seven cases from two to eight days, and in the remaining two from ten to thirteen days, whereas in two of the three successful cases the mosquito had been kept for twelve days or longer.”  In the third case, that of Dr. Lazear, the facts are stated in the report of the board as follows: 

Case 3.  Dr. Jesse W. Lazear, Acting Assistant Surgeon U.S.  Army, a member of this board, was bitten on August 16, 1900 (Case 3, Table III) by a mosquito (Culex fasciatus), which ten days previously had been contaminated by biting a very mild case of yellow fever (fifth day).  No appreciable disturbance of health followed this inoculation.

On September 13, 1900 (forenoon), Dr. Lazear, while on a visit to Las Animas Hospital, and while collecting blood from yellow fever patients for study, was bitten by a Culex mosquito (variety undetermined).  As 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