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by its victim, must vary in its chemical composition in different species 

 of gnats, thereby accounting for the difference in the sensations occasioned 

 by their sting. It is quite possible, therefore, that the presence of that 

 liquid may constitute in the sting of the culex mosquito au appropriate soil 

 for the development of the yellow fever germ, whereas the same germ 

 would remain sterile in the sting of other species of culex. 



Another objection of a clinical character was made to our considering 

 as cases of mild yellow fever attacks of nonalbuminuric fever observed 

 in our inoculated subjects, either within the plausible limits of incubation 

 or later on, with the result of rendering them immune against subsequent 

 attacks of albuminuric yellow fever. To this objection an answer is given 

 by the present statistics themselves, inasmuch as among fifty -six inoculated 

 and non-inoculated subjects mentioned therein and who resided during 

 periods varying between three and seven consecutive years in the city of 

 Havana, one-half have acquired their immunity exclusively through non- 

 albuminuric attacks suffered during the first three years after their 

 arrival here. If the objection turned out to be well grounded, it would only 

 prove that what we had considered as a partial immunity had been a 

 complete one in ninety per cent, of our inoculated subjects. 



I have distributed our sixty-seven inoculated subjcts into six groups : 



Group I. Fifteen whose observation is yet incomplete, not having 

 resided three years in Havana, nor experienced any form of yellow 

 fever. 



Group II. Twelve who experienced, within a period of days varying 

 between three and twenty-five, after the inoculation, an attack of fever 

 with or without albuminuria. 



Group III. Twelve who did not experience any pathogenic effects 

 within the twenty-five days following the inoculation, nor any other 

 febrile attack subsequently, that could be referred to the yellow fever 

 infection. 



Group IV. Twenty-four who did not experience pathogenic effects 

 within the twenty-five days, but subsequently had fevers of a mild type, 

 either non-albuminuric or with slight or transient albuminuria. 



Group V. Three who experienced no pathogenic effects after the 

 inoculation, but were subsequently attacked with regular albuminuric 

 yellow fever (severe in two cases), but recovered. 



Group VI. One who not having experienced pathogenic effects after 

 the inoculation, was attacked some months later, and after exposure to an 

 infection of unusual intensity, with fatal yellow fever. 



After excluding the fifteen incomplete observations of Group I., fifty- 

 two cases remain to be considered which may be conveniently arranged 

 under three heads : 



