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mental cases; and the rest may be studied, by a more humane plan, in 

 infected foci, with material obtained from natural cases of yellow fever. 

 In a locality such as Havana, where the question of destroying all the 

 mosquitoes of the Stegomyia species is very problematic, and which is only 

 just completing its first year of immunity from yellow fever, there is more 

 than the risk incurred by the inoculated person to be considered. There is 

 the possibility that, in spite of all precautions, a stray stegomyia may 

 reach the experimental case unperceived, and that a focus of yellow fever 

 may thereby be originated. I am therefore of opinion that in Cuba such 

 inoculation experiments upon human subjects must be strictly forbidden, 

 and that the handling of infected mosquitoes must only be permitted to 

 persons well acquainted with the dangers and familiar with the manner 

 of averting them. 



Reverting to the order of ideas in which my method for stamping out 

 yellow fever had been conceived, I shall now briefly enumerate the most 

 essential conculsions which had been reached by me and included in my 

 mosquito theory previous to 1898. Those conclusions were : 



1. That the germ of yellow fever is only pathogenic for human beings 

 when introduced by inoculation. 



2. That the regular process by which the inoculation of the germ is 

 accomplished in nature is through the bites of the Culex mosquito 

 (Stegomyia fasciata Theo.), the insect having previously become 

 contaminated through the act of biting yellow fever patients within the 

 first five or six days of their attack. 



3. That although the bites of a recently contaminated mosquito can 

 only produce a mild attack of yellow fever, or simply confer latent 

 immunity without eliciting any pathogenic reaction, the bites of the same 

 insect, when its contamination dates back several days or weeks, may be 

 expected to produce severe or fatal attacks of yellow fever. 



4. That the yellow fever mosquitoes, after they have once been 

 contaminated, retain the power of inoculating the disease during the rest 

 of their lives if they have chances of biting non-immunes. 



5. That the essential conditions for stamping out yellow fever from 

 an infected locality are : (a) to protect yellow fever patients from the bites 

 of the special yellow fever mosquitoes; (o) to destroy all the mosquitoes 

 which may have reached yellow fever patients; (c) not to allow non- 

 immunes to enter the infected zone until the last of the contaminated 

 insects may be supposed to have died; (d) to lessen the chances of 

 propagation by adopting adequate measures calculated to prevent the 

 multiplication of mosquitoes in general. 



6. In 1898, when I reckoned the longevity of the Stegomyia at thirty- 

 five to forty days, as a maximum, I had fancied that my theory would be 

 improved by including also the possibility that the infected insects might 



