YELLOW FEVER AND MOSQUITOES. 233 



Nothing could point more forcibly to tlie source of this infection than the 

 order of the occurrence of events at this camp. Tlie precision with which the 

 infection of the individual followed the bite of the mosquito left nothing to be 

 desired in order to fuUlll the requirements of a scientific experiment. 



In summing up their results at the conclusion of this report the fol- 

 lowing statement is made : 



Out of a total of 18 non-immunes whom we have inoculated with contami- 

 nated mosquitoes, since we began this line of investigation, 8, or 44.4 per cent., 

 have contracted yellow fever. If we exclude those individuals bitten by mos- 

 quitoes that had been kept less than twelve days after contamination, and which 

 were therefore probably incapable of conveying the disease, we have to record 

 eight positive and two negative results — 80 per cent. 



In a still later report (May, 1901) Dr. Reed says: "We have thus far suc- 

 ceeded in conveying yellow fever to twelve individuals by means of the bites of 

 contaminated mosquitoes." 



The non-immune individuals experimented upon were all fully in- 

 formed as to the nature of the experiment and its probable results and 

 all gave their full consent. Fortunately no one of these brave volun- 

 teers in the cause of science and humanity suffered 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 responsibility 

 which rested upon them. That these experiments were justifiable under 

 the circumstances mentioned is, I believe, beyond question. In no other 

 way could the fact established have been demonstrated and the knowl- 

 edge 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 contracted 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 pos- 

 sible care and after their recovery they had the advantage of being 'im- 

 munes' who had nothing further to fear from the disease which has 

 caused the death of thousands and tens of thoiisands of Spanish soldiers 

 and immigrants who have come to Cuba under the orders of their Gov- 

 ernment or to seek their fortunes. 



The experiments already referred to show in the most conclusive 

 manner that the blood of yellow-fever patients contains the infectious 

 agent, or germ, to which the disease is due, and this has been further 

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

 ment was made by Dr. Eeed at 'Camp Lazear' upon four individuals, 

 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 the bend of the elbow on the first or second day of sick- 

 ness and was injected subcutaneously into the four non-immune in- 



