TRANSMISSION OF YELLOW FEVEE BY MOSQUITOES. 663 



ho«t" to .Still otber.s. Thius the epidemic extends, at first .slowlv as 

 from house to house, then more rapidly, as by geometricalpro- 

 gression. ^ 



It will be seen that the essential difference between the successful 

 experiments of the board of which Doctor Reed is president, and the 

 unsuccessful experiments of Finlay consist in the length of time dur- 

 ing which the mosquitoes were kept after filling themselves with l)lood 

 from a yellow-fever patient. In Finlay's experiments the interval 

 was usually short— from two to five or six days, and it will be noted 

 that in the experiments of Reed and his associates the result was inva- 

 riably negative when the insect had been kept for less than eight days 

 (seven cases). 



Having obtained what they considered satisfactory evidence that yel- 

 low fever is transmitted by mosquitoes. Doctor Reed and his associates 

 proceeded to extend their experiments for the purpose of establishing 

 the fact in such a positive manner that the luedical profession and the 

 scientific world generally might be convinced of the reliability of the 

 experimental evidence upon which their conclusions were based. 

 These conclusions, which have been fully justified by their subsequent 

 experiments, were stated in their "Preliminary note "as follows: 



1. Bacillus icteroidcs (Sanarelli) stands in no causative relation to yellow fever, 

 but, when present, should be considered as a secondary invader in this disease. 



2. The mosquito serves as the intermediate host for the parasite of yellow fever. 



In ''An additional note" read at the Pan-American ]\Iodical Con- 

 gress, held in Havana, Cuba, Februar}- 4-7, 1901, a report is made of 

 the further experiments made up to that date. In order that the abso- 

 lute scientific value of these experiments may be full}' appreciated, I 

 shall quote quite f reeh' from this report with reference to the methods 

 adopted for the purpose of excluding all sources of infection other 

 than the mosquito inoculation: 



In order to exercise perfect control over the movements of those individuals who 

 were to be subjected to experimentation, and to avoid any other possible source of 

 infection, a location was selected in an open and uncultivated field, about 1 mile from 

 the town of Quemados, Cuba. Here an experimental sanitary station was estab- 

 lished under the complete control of the senior member of this board. This station 

 was named Camp Lazear, in honor of our late colleague, Dr. Jesse W. Lazear, acting 

 assistant surgeon, United States Army, who died of yellow fever while courageously 

 investigating the causation of this disease. The site selected was well drained, freely 

 exposed to sunlight and winds, and from every point of view satisfactory for the 

 purposes intended. 



The personnel of this camp consisted of two medical officers. Dr. Roger P. Ames, 

 acting assistant surgeon. United States Army, an immune, in immediate charge; Dr. 

 E. P. Cooke, acting assistant surgeon. United States Army, nonimmime; one acting 

 hospital steward, an immune; nine privates of the hospital corps, one of whom was 

 immune, and one immune ambulance driver. 



For the quartering of this detachment, and of such nonimmune individuals as 

 should be received for experimentation, hospital tents, properly floored, were pro- 



