255 



those of the yellow fever virus are brought into play in one and the same 

 operation, might it not happen that immunizing faculties would be deve- 

 loped in the leucocytes against yellow fever toxines of moderate intensity, 

 as well as against the mosquito venom? A summary account of the ex- 

 periments perfomed by myself (and some also by my friend Dr. Delgado) 

 during the last twelve years, will enable the reader to judge for himself. 

 The experiment has consisted in first applying a captive mosquito to a 

 yellow fever patient, allowing it to introduce its lance and to fill itself 

 with blood; next, after the lapse of two or more days, applying the same 

 mosquito to the skin of a person who is considered susceptible to yellow 

 fever; and finally, observing the effects, not only during the first few 

 weeks, hut during periods of several years, so as to appreciate the amount 

 of immunity that should follow. 



Between the 30th of June 1881 and the 2d of December 1893, eighty- 

 eight persons have been so inoculated. All were white adults, uniting the 

 conditions which justify the assumption that they were susceptible to 

 yellow fever. Only three were women. The chronological distribution of 

 the inoculations was as follows : 



Seven in 1881, ten in 1883, nine in 1885, three in 1886, twelve in 1887, 

 nine in 1888, seven in 1889, ten in 1890, eight in 1891, three in 1892, and 

 ten in 1893. The following table will show the length of time during 

 which the "inoculated" resided in Havana (as also some ten or twelve who 

 resided most of the time in Cienfuegos). During this time the inoculated 

 were under observation, so far, at least, as to obtain information about any 

 attack of yellow fever that was suffered by them (with the exception of 

 only one case, that of a youth who was lost sight of after the inoculation.) 



Result unknown in. . . 1 case. Four years in 28 cases. 



Less than one year in. 11 cases. Five years in 2 „ 



One year in 3 „ Six years in 8 „ 



Two years in 12 „ Seven to 10 yrs. in. . . 9 „ 



Three years in 14 „ 



Total 87 cases. 



The yellow fever patients upon whom the mosquitoes were contaminat- 

 ed were, almost in every instance, well marked cases of the albuminuric 

 or melano-albuminuric forms, in the second, third, fourth, fifth, or sixth, 

 day of the disease. In some of the susceptible subjects, the inoculation was 

 reapeated when the source of contamination appeared uncertain. 



Among the eighty-seven who have been under observation, the follow- 

 ing results have been recorded : 



1. Within a term of days, varying between five and twenty-five after 

 the inoculation, one presented a mild albuminuric attack, and thirteen only 

 "acclimation fevers". 



19 



