202 MOSQUITOES OF NORTH AMERICA 
single infected mosquito. They crushed it up and fed it to 25 new insects, and 
these latter, ground up in their turn, were distributed among 200 others. Of 
these, 25 were devoted to a fourth experiment, while the major part of the others 
were ground up in physiological water, and the liquid injected, after filtration 
through a metallic sieve, into the veins of a kid. The result was negative. Ten 
more were allowed to puncture a man, but without result. This lack of success 
did not discourage them. They continued the work, and repeated the injections 
into the kid, which thus received the extract of about two thousand mosquitoes. 
Serum from this kid, tried fifteen days after the last inoculation, was shown to 
be inactive. After the second passage the cultures were without doubt sterile, 
but unfortunately without the investigators having perceived it, and this is, in 
fact, the most serious obstacle to this kind of culture. With each passage it is 
necessary to experiment with a man in order to determine the success or non- 
success. 
Very great praise is due to the French investigators for the care, persistence 
and ingenuity of their experimental work. They made important discoveries, 
strengthened and helped to fix the belief of the advanced medical profession, and 
indicated important lines of work for future research. 
THE LAREDO OUTBREAK OF 1903. 
The establishment of the fact that yellow fever is transmitted by Aédes calopus 
was followed by admirable mosquito extermination work in the city of Havana 
by the United States Army authorities. The work was put in charge of Dr. W. 
C. Gorgas, of the Army, and quickly produced the most beneficial results. Some 
details concerning this work are given later in this volume among the examples 
of successful anti-mosquito work. 
In 1903 it became evident that yellow fever was epidemic in the town of 
Laredo, Texas, and in the city of Nuevo Laredo, Mexico, immediately across 
the Rio Grande from Laredo. It was not until the end of September that the 
disease was definitely ascertained to be yellow fever, having been reported up to 
that time to be dengue; but upon September 25 the public health officials took 
charge of the situation and immediately began work based upon anti-mosquito 
measures. From September 25 to November 30 there were 1050 cases of yellow 
fever, of which 691 were Mexicans and 359 Americans. The number of deaths 
was 103, 95 being Mexicans and 8 Americans. The measures adopted and at 
once put into effect were practically those which had been instituted in Cuba, 
and which consisted in isolation of patients, protection by mosquito bars, fumi- 
gation of houses, and the oiling of water receptacles. We mention this Laredo 
work as a demonstration additional to those of the mosquito results in Cuba and 
Brazil, and as nothing else. Some of the conclusions reached by Surgeon G. M. 
Guiteras in his report to Surgeon-General Wyman may be mentioned: 
“1. The results obtained through the efforts to combat the yellow fever epi- 
demic at Laredo go to demonstrate that the mosquito (Stegomyia fasciata) is 
the only means of transmitting yellow fever and that the efforts to destroy the 
same were productive of much good, greatly limiting the number of cases. 
