238 Arthropods as Essential Hosts of Pathogenic Protozoa 
showed that the so-called Brill’s disease, studied especially in New 
York City, is identical with the typhus fever of Mexico and of 
Europe. 
The conditions under which the disease occurs and under which 
it spreads most rapidly are such as to suggest that it is carried by 
some parasitic insect. On epidemiological grounds the insects most 
open to suspicion are the lice, bed-bugs and fleas. 
In 1909, Nicolle, Comte and Conseil, succeeded in transmitting 
typhus fever from infected to healthy monkeys by means of the 
body louse ( Pediculus corporis). Independently of this work, 
Anderson and Goldberger had undertaken work along this line in 
Mexico, and in 1910 reported two attempts to transmit the disease 
to monkeys by means of body lice. The first experiment resulted 
negatively, but the second resulted in a slight rise in temperature, 
and in view of later results it seems that this was due to infection 
with typhus. 
Shortly after, Ricketts and Wilder (1910) succeeded in transmitt¬ 
ing the disease to the monkey by the bite of body lice in two experi¬ 
ments, the lice in one instance deriving their infection from a man 
and in another from the monkey. Another monkey was infected 
by typhus through the introduction of the feces and abdominal 
contents of infested lice into small incisions. Experiments with 
fleas and bed-bugs resulted negatively. 
Subsequently, Goldberger and Anderson (19126) indicated that 
the head louse ( Pediculus humanus ) as well, may become infected 
with typhus. In an attempt to transmit typhus fever (Mexican 
virus) from man to monkey by subcutaneous injection of a saline 
suspension of crushed head lice, the monkeys developed a typical 
febrile reaction with subsequent resistance to an inoculation of 
virulent typhus (Mexican) blood. In one of the three experiments 
to transmit the disease from man to monkey by means of the bite 
of the head louse, the animal bitten by the presumably infected head 
lice proved resistant to two successive immunity tests with viru¬ 
lent typhus blood. 
In 1910, Ricketts and Wilder reported an experiment undertaken 
with a view to determining whether the young of infected lice were 
themselves infected. Young lice were reared to maturity on the 
bodies of typhus patients, so that if the eggs were susceptible to 
infection at any stage of their development, they would have every 
opportunity of being infected within the ovary. The eggs of these 
infected lice were obtained, they were incubated, and the young lice 
