Juan Finlay (1833 - 1915)
twenty years of his professional life, renowned Cuban physician
and scientist Carlos J. Finlay stood at the center of a vigorously
debated medical controversy. The etiology of yellow fever -- its
causes and origins -- had puzzled medical practitioners since the
earliest recorded cases of the disease in the fifteenth and sixteenth
centuries. Periodic epidemics of yellow fever ravaged the population
of Finlay's native Cuba, particularly affecting the citizens of
Havana, where he set up a medical practice in 1864. Finlay was
intensely interested in epidemiology and public health, and his
initial work on cholera -- the result of a severe outbreak of the
disease in Havana in 1867 -- challenged the received wisdom of medical
His conclusion that
the disease was waterborne, though later verified, was rejected
by publishers at the time. Finlay soon afterwards began research
on yellow fever, publishing his first paper on it in 1872. Here
the same keen observations and logical deductions which informed
his analysis of cholera lead him to propose in 1881 that the Culex
mosquito be "hypothetically considered as the agent of transmission
of yellow fever."
 This time the paper was published, but the wide professional
circulation of The Annals of the Academy of Medical, Physical,
and Natural Sciences of Havana did not assure Finlay of widespread
support. Indeed, only one other Cuban physician, Claudio Delgado,
rallied to Finlay's side in those early years.
Finlay himself recognized
the difficulties inherent in his revolutionary proposal: "I
understand but too well," he concluded in the now famous 1881
paper, "that nothing less than an absolutely incontrovertible
demonstration will be required before the generality of my colleagues
accept a theory so entirely at variance with the ideas which have
until now prevailed about yellow-fever."
 From 1881 to 1900, Finlay pursued a campaign of 102 experimental
inoculations on human volunteers, with the aim of demonstrating
both the truth of his hypothesis and the possibility of inducing
immunity to the disease. Finlay did believe that he had produced
cases of yellow fever by mosquito inoculation, although the larger
public health community remained skeptical. George Miller Sternberg,
later to become Surgeon General of the United States Army, offered
an essential critique of Finlay's experiments: that the participants
were never sufficiently isolated from the general population to
eliminate the possibility of contracting fevers from sources other
than Finlay's mosquitoes. This and the inconsistency with which fevers developed in the
experimental participants kept the mosquito theory on the margins.
Nevertheless, Finlay's expertise gained a place for him among the
leading public health practitioners in Havana, and his advice and
experiences proved invaluable to the United
States Army Yellow Fever Commission. When the Commission decided
to test the mosquito theory, Finlay provided the mosquitoes, and
with the Commission's first scientifically valid success, Walter
Reed wrote triumphantly, "The case is a beautiful one,
and will be seen by the Board of Havana Experts, to-day, all of
whom, except Finlay, consider the theory a wild one!" The full run of experiments at
Camp Lazear vindicated Finlay's two-decade-long struggle. In the
glow of that early success, Reed acknowledged that "it was
Finlay's theory, & he deserves much for having suggested it."
 William Crawford Gorgas, who later applied the results
of the experiments to a public health campaign which made possible
the construction of the Panama Canal, characterized Finlay's contribution
in this way: "His reasoning for selecting the Stegomyia
as the bearer of yellow fever is the best piece of logical reasoning
that can be found in medicine anywhere."
Finlay concluded his career as the Chief Sanitary Officer of Cuba,
a position he held for eight years before retiring in 1909.
 Carlos J. Finlay, "El mosquito hipotéticamente
considerado como agent de transmision de la fiebre amarilla,"
Anales de la Real Academia de Ciencias Médicas Físicas y Naturales
de la Habana 18 (1881): 147-169, reprinted in: Medical
Classics 2 (February, 1938) 6: 590.
 Finlay, "El mosquito," Anales de la
Real Academia 18 (1881): 147-169, reprinted in: Medical
Classics 2 (February, 1938) 6: 610, 611.
 George Miller Sternberg, "Dr. Finlay's Mosquito
Inoculations," American Journal of the Medical Sciences
CII (1891) 6: 629, 630; George Miller Sternberg, "The Transmission
of Yellow Fever by Mosquitoes," The Popular Science Monthly
LIX (July, 1901) 3: 226-228.
 Letter from Walter Reed to Albert E. Truby, 10 December
1900, published in: Albert Ernest Truby, Memoir of Walter
Reed: the Yellow Fever Episode (New York: Paul B. Hoeber,
Inc., 1943), figure 26.
 Letter from Walter Reed to Emilie Lawrence Reed,
9 December 1900, Philip S. Hench Walter Reed Yellow Fever Collection,
Claude Moore Health Sciences Library, Department of Historical
Collections and Services, accession number: 02231001.
 Letter from William Crawford Gorgas to Walter Reed,
6 February 1902, Hench Reed Yellow Fever Collection, accession