TRANSMISSION OF YELLOW FEVER BY MOSQUITOES. 665 



In summing- up their results, at the eonehisio,. cf this report the 

 toUowing statement is niiide: 



Out of a total of IS noniu.nu.nes whon. we have inoculated with .outan.inated 

 mosquitoe. since we began thi.s line of investigation 8, or 44.4 per cent, have con- 

 tracted yellow fever. If we exclude those individual., bitten bv n.osc.uitoes that had 

 been kept less than twelve days aft«r contamination, and whi(,h were therefore 

 probably mcapaole of conveying the disease, we have to rwonl 8 positive and 2 

 negative results— 80 i>er cent. 



In a still later report (May, l!»ul) Doctor Keed savs: " We have 

 thus far succeeded in conveyinu- yellow fever to twelve individuals by 

 means of the bites of contaminated mosquitoes." 



The nonimmune individuals experimented upon were all fully 

 informed as to the nature of the experiiuent and its probable results, 

 and all gave their fidl consent. Fortunately no one of these brave 

 volunteers in the cause of science and hinnanity sutfered a fatal attack 

 of the disease, although several were very ill and gave great anxiety 

 to the members of the board, who fully appreciated the grave respon- 

 sibility which rested upon them. That these experiments were justifi- 

 able luider the circiunstances mentioned is, 1 believe, beyond (inestion. 

 In no other way could the fact established have been demonstrated, 

 and the knowledge gained is of inestimable value as a guide to reliable 

 measures of prevention. Already it is being applied in Cuba, and 

 without doubt innumerable lives will be saved as a result of these 

 experiments showing the precise method by which yellow fever is con- 

 tracted by those exposed in an ''infected locality." Some of these 

 volunteers were enlisted men of the United States Army and some 

 were Spanish immigrants who had recently arrived in Cuba. When 

 taken sick, they received the best possible care, and after their recov- 

 er^' they had the advantage of being '"immunes" who had nothing 

 further to fear from the disease which has caused the death of thou- 

 sands and tens of thousands of Spanish soldiers and inunigrants who 

 have come to Cul)a under the orclers of their Government or to seek 

 their fortunes. 



The experiments already referred to show in the most conclusive 

 manner that the blood of yellow fever patients contains tho infectious 

 agent or germ to which the disease is due, and this has ])een further 

 demonstrated by direct inoculations from man to man. This experi- 

 ment was made by Doctor Keed, at Camp Lazear, upon four individ- 

 uals, who freely consented to it, and in three of the four a typical 

 attack of yellow fever resulted from the blood injection. The blood 

 was taken from a vein at tlie bend of the elbow on the lirst or second 

 day of sickness and was injected subcutaneou.sly into the four non- 

 immune individuals, the amount l)eing in one positive case 2 c. c, in 

 one 1.5 c. c, and in one 0.5 c. c In the *'ase attended with a negative 

 result, a Spanish immigrant, a mosquito inoculation also proved to bo 

 SM 1900 46 



