YELLOW FEVER AND MOSQUITOES. 231 



through the 'intermediate host' to still others. Thus the epidemic ex- 

 tends, at first slowly as from house to house, then more rapidly, as by 

 geometrical progression. 



It will be seen that the essential difference between the successful ex- 

 periments of the board of which Dr. Eeed is president and the unsuc- 

 cessful experiments of Finlay consists of the length of time during which 

 the mosquitoes were kept after filling themselves with blood from a yel- 

 low-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 ex- 

 periments of Eeed and his associates the result was invariably negative 

 when the insect had been kept for less than eight days (7 cases). 



Having obtained what they considered satisfactory evidence that 

 yellow fever is transmitted by mosquitoes, Dr. Eeed and his associates 

 proceeded to extend their experiments for the purpose of establishing 

 the fact in such a positive manner that the medical 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 experi- 

 ments were stated in their 'Preliminary Note' as follows: 



1. Bacillus icteroides (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 Kote' read at the Pan-American Medical Con- 

 gress held in Havana, Cuba, February 4-7, 1901, a report is made of the 

 further experiments made up to that date. In order that the absolute 

 scientific value of these experiments may be fully appreciated I shall 

 quote quite freely 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 one mile from the tovvTi of Quemados, Cuba. Here an experimental sani- 

 tary station was established under the complete control of the senior member of 

 this Board. This station was named Camp Lazear, in honor of our late col- 

 league. Dr. Jesse W. Lazear, Acting Assistant Surgeon U. S. A., 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 U. S. A., an immune,' in immediate charge; Dr. 

 R. P. Cooke, Acting Assistant Surgeon U. S. A., non-immune; one acting hos- 

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

 immune, and one immune ambulance driver. 



