202 
Arthropods as Hosts of Pathogenic Protozoa 
include the important circumstance that the faculty of transmitting 
the yellow fever germ need not be limited to the parent insect, 
directly contaminated by stinging a yellow fever patient (or per¬ 
haps by contact with or feeding from his discharges), but may be 
likewise inherited by the next generation of mosquitoes issued from 
the contaminated parent.” He believed that the bite of a single 
mosquito produced a light attack of the disease and was thus effec¬ 
tive in immunizing the patient. Throughout the period, many 
apparently successful attempts to transmit the disease by mosqui¬ 
toes were made. In the light of present day knowledge we must 
regard these as defective not only because possibility of other infec¬ 
tion was not absolutely excluded but because no account was taken 
of the incubation period within the body of the mosquito. 
In 1900, while the American army was stationed in Cuba there 
occurred an epidemic of yellow fever and an army medical board was 
appointed for‘‘the purpose of pursuing scientific investigations with 
reference to the acute infectious diseases prevalent on the island.” 
This was headed by Walter Reed and associated with him were James 
Carroll, Jesse W. Lazear and Aristides Agramonte, the latter a Cuban 
immune. For a detailed summary of this work the lay reader can¬ 
not do better than read Dr. Kelly’s fascinating biography ‘‘Walter 
Reed and Yellow Fever.” 
Arriving at the army barracks near Havana the Commission first 
took up the study of Bacillus icteroides, the organism which Sanarelli, 
an Italian physician, had declared the causative agent in yellow fever. 
They were unable to isolate this bacillus either from the blood during 
life or from the blood and organs of cadavers and therefore turned 
their attention to Finlay’s theory of the propagation of yellow fever 
by means of the mosquito. In this work they had the unselfish 
and enthusiastic support of Dr. Finlay himself, who not only consulted 
with them and placed his publications at their disposal, but furnished 
eggs from which their experimental mosquitoes were obtained. 
Inoculations of eleven non-immunes through the bite of infected 
mosquitoes were made, and of these, two gave positive results. The 
first of the two was Dr. Carroll who allowed himself to be bitten 
by a mosquito which had been caused to feed upon four cases of 
yellow fever, two of them severe and two mild. The first patient 
had been bitten twelve days before. 
Three days after being bitten, Dr. Carroll came down with a 
typical case of yellow fever. So severe was the attack that for three 
