662 TRANSMISSION OF YELLOW FEVER BY MOSQUITOES. 



twelve daj's or longer. In the third case — that of Doctor Lazear — the 

 facts are stated in the report of the board as follows: 



Case 3. — Dr. Jesse AV. Lazear, acting assistant surgeon. United States Army, a mem- 

 ber of this board, was bitten on August 16, 1900 (case 3, Table HI), by a mosquito 

 {Culex fasciaius), which ten days previously had been contaminated by biting a very 

 mild case of yellow fever (fifth day). No appreciable disturl)ance of health followed 

 this inoculation. 



On September 13, 1900 (forenoon), Doctor Lazear, while on a visit to Las Animas 

 Hospital, and while collecting blood from yellow-fever patients for study, was l)itten 

 by a Culex mosquito ( variety undetermined) . As Doctor 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 satisfie<l its hunger. 



On the evening of September 18, five days after the l)ite, Doctor Lazear complained 

 of feeling "out of sorts," and had a chill at 8 p. m. 



On September 19, 12 o'clock noon, his temperature was 102.4°; jnilse, 112. His 

 eyes were injected and his face suffused. At 3 p. m. temperature was 103.4°; pulse, 

 104; 6 p. m. temperature, 103.8°, and pulse, 106. Albumin api)eared in the urine. 

 Jaundice appeared on the third day. The sul)se«juent 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 a result of the ))ite by a mosquito ""while on a visit to 

 Las Animas Hospital," although Doctor Lazear himself was thor- 

 oughl}' convinced that this was the direct cause of his attack. 



The inference drawn l)y Doctor Keed and his associates from the 

 experiments thus far made was that yellow fever \\\&y 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 tilled itself with blood from a 3'ellow 

 fever patient in the earlier stages of the disease. In other words, that 

 a certain period of incu])ation is required in the bod}' of the insect 

 before the germ reaches its salivaiT glands, and consequently before 

 it is able to inoculate an individual with the germs of 3'ellow 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. AVhen a case is imported to one of our Southern 

 seapoi't cities from Havana, Vera Cruz, or some other endenjic focus 

 of the disease, an interval of two weeks or more occurs before second- 

 arv cases are developed as a result of such importation. In the light 

 of our present knowledge this is readih' understood. A certain num- 

 ber of mosquitoes, having filled themselves with blood from this first 

 case, after an interval of twelve days or more bite nonimmune individ- 

 uals living in the vicinit}', and these individuals, after a brief period 

 of incubation, fall sick with the disease; being bitten by other mos- 

 quitoes thej' serve to transmit the disease through the "intermediate 



