EXPERIMENTS IN TRANSMISSION 249 
inoculation of the existing mosquitoes. Finally, the importance of the experi- 
ments from the point of view of prophylaxis can not be disregarded.” 
This case is so extremely important that more space must be devoted to it. 
The year following the first announcement just quoted, fuller details were given 
in the Annals of the Pasteur Institute for January, 1906, in which the symptoms 
of the infected patient are carefully given, day by day, and the daily tempera- 
ture is charted, leaving the case fairly open to the inspection and possible criti- 
cism of yellow-fever experts. The investigators consider a light attack of 
yellow fever as perfectly proved, and state that the absence of albumen, the 
lowering of the temperature after forty-eight hours, and the rapidity of the 
convalescence particularly show the mildness of the case. They consider that the 
immunity to a subsequent attack, which they tested by later inoculations with 
infected mosquitoes, is also strong evidence of the validity of the first attack, 
and in fact confirms it rigorously. They call especial attention also to the fact 
that the interval between the time of the first infective bite, 4 o’clock in the after- 
noon on the 10th of March, and the appearance of the first symptoms of yellow 
fever at midday on the 14th of March, being three days and twenty hours, or 
ninety-two hours, is exactly the interval most commonly observed in experi- 
ments in the transmission of yellow fever by the bite of Aédes calopus. They 
point out that in the twenty-six experimental cases followed by positive results 
at Havana and in Brazil eighteen cases showed symptoms of the fever in the 
course of the fourth day following the bite. 
They considered the possibility whether, in spite of their careful watch over 
the subject, who as a matter of fact lived with one of them in the laboratory, 
some chance circumstance had perhaps exposed him to inoculation other than 
the experimental puncture of the hereditarily infected mosquito. But they 
think that there was no chance that this could have occurred under the precise 
conditions. 
In the article just cited the French writers admit that it is impossible to draw 
unassailable conclusions from an isolated case. However they elaborate upon 
the importance of this discovery as accounting for the return of recently stamped- 
out epidemics at a period which may be comparatively short but too long to 
permit of its direct carriage by adult mosquitoes infected before the epidemic 
was stamped out. They cite the return of the 1889 epidemic at Campinas as a 
possible example. Reverting again to the benignity of the case produced by the 
hereditarily infected mosquito, they ask if this was not due to an attenuation 
of the virus which had passed through the egg and larval stages of the insect. 
They state that among their experimental cases bitten by directly infected mos- 
quitoes they found a certain proportion which were benign, and concluded that, 
aside from individual resistance to the disease, there are conditions as yet un- 
known which bring about an increase or an attenuation of the virus in the mos- 
quito. They argued further that it is known that in countries where yellow 
fever occasionally exists there are false epidemics—an illness known under the 
name of inflammatory fever. It differs from yellow fever by the mildness of its 
attack and by the absence of mortalities. One of these writers studied in 1882 a 
