Inoculations for Yellow Fever 

 By Means of Contaminated Mosquitoes X) 



At the time when my former article was written 1) I observed that 

 the figures there given were not considered by me, ' ' from a statistical point 

 of view, to afford any definite clew either in favor or against the 

 prophylactic value of my inoculations". In fact, neither the number of my 

 experiments nor the length of time during which the parties inoculated 

 had been under observation could at that time justify any scientific; 

 deductions. Now, however, the case is different ; I have on record a series 

 of sixty-seven persons, including all those whom, in collaboration with Dr. 

 Delgado, I have inoculated since 1881, by means of contaminated mosquit- 

 oes, in the manner explained in my previous article. All were Europeans, 

 with few exceptions natives of Spain, young adults recently arrived in 

 Cuba and presenting the usual conditions which imply liability to contract 

 yellow fever. Among the sixty-seven a considerable number, fifty-two, are 

 considered as acclimated, either from the fact that they have resided in 

 the infected quarters of the city of Havana (the old town) during periods 

 varying between three and seven years, or in consideration of their having 

 experienced fevers which are attributed to the yellow fever infection, 

 though of a mild type in the vast majority of the cases. Two parallel groups, 

 one of thirty-three inoculated persons and the other of thirty-two not 

 inoculated, both offering to all intents and purposes such similarity (as 

 to susceptibility and exposure) as can seldom be obtained, afford a reliable 

 foundation for a fair and unbiassed comparision. I consider, therefore, 

 that the time is now come when some practical inferences may be drawn, 

 and, as far as they go, I am happy to say that they agree with my former 

 expectations. 



The statistical method of demonstration is, at best, a tedious and a 

 slow process, but it can boast of great triumphs, such as are recorded in 

 the instances of Jenner and Pasteur, who have had to rely exclusively on 



1) The American Journal of the Medical Sciences, Sept. 1891. 



2) "Yellow Fever: Its Transmission by Means of the Culex Mosquito". The 

 American Journal of the Medical Sciences, October, 1886, p. 395. 



