110 INSECTS AND DISEASE 
was held by the great majority to be a contagious disease, 
communicated directly from the sick to the healthy. This 
was of course the belief of the general public, and a general 
dread of infection and fear of approaching the sick added 
much to the horrors of the epidemics. But many facts 
appeared to controvert this theory of direct contagion, 
and gradually the opinion that yellow fever was a non- 
contagious and non-communicable disease became prevalent 
among the profession. This theory, however, failed to 
explain all the facts, and after much controversy, a middle 
position became generally held—that while not directly 
communicable from the sick to the healthy, yellow fever’ 
was spread by emanations from the sick which required 
a suitable nidus in which to germinate and develop before 
they attacked the healthy, and that this nidus was furnished 
by clothing, furniture and various articles of merchandise 
to which collectively was appled the term fomites. 
This was the received theory in the year 1900. Many 
investigations had been made to discover the causal organism 
of the disease, but none had succeeded, though several 
observers had isolated organisms which were at first supposed 
to be those sought for. Meanwhile, the disinfection of 
fomites was the official weapon with which epidemics 
were combated. Dense ignorance prevailed as to the real 
mode of spread of the disease, and on this ignorance was 
based an official routine which was of small value for the 
purpose for which it was intended. 
In this year, 1900, yellow fever appeared among the 
American troups in the island of Cuba, and a commission 
of medical officers of the United States Army was appointed 
to investigate the etiology of the disease. The head of 
this commission was the late Walter Reed, a U.S. Army 
surgeon, and to him we owe our present knowledge of the pro- 
pagation of yellow fever. He was to some extent anticipated. 
Dr. Carlos Finlay, a physician of Havana, had promulgated 
the theory that yellow fever was spread by mosquitos, 
without, however, producing any cogent evidence in its 
favour, and he had few if any adherents. Nevertheless, 
some observations made by Reed on an epidemic in some 
barracks near Havana disposed him to believe that Finlay’s 
theory had much to commend it, and was at least worth 
