s whom we tried to infect by means of
fomites [cloth and other material generally capable of carrying
germs] under particularly favorable circumstances, we did not
succeed in a single instance."

It is evident that in view of our present knowledge relating to the mode
of transmission of yellow fever, the preventive measures which have
heretofore been considered most important, that is, isolation of the
sick, disinfection of clothing and bedding, and municipal sanitation,
are either of no avail or of comparatively little value. It is true that
yellow fever epidemics have resulted, as a rule, from the introduction
to a previously healthy locality of one or more persons suffering from
the disease. But we now know that its extension did not depend upon the
direct contact of the sick with the nonimmune individuals and that
isolation of the sick from such contact is unnecessary and without
avail. On the other hand, complete isolation from the agent which is
responsible for the propagation of the disease is all-important. In the
absence of a yellow fever patient from which to draw blood the mosquito
is harmless, and in the absence of the mosquito the yellow fever patient
is harmless--as the experimental evidence now stands. Yellow fever
epidemics are terminated by cold weather because the mosquitoes die or
become torpid. The sanitary condition of our southern seaport cities is
no better in winter than in summer, and if the infection attached to
clothing and bedding it is difficult to understand why the first frosts
of autumn should arrest the progress of an epidemic. But all this is
explained now that the mode of transmission has been demonstrated.

Insanitary local conditions may, however, have a certain influence in
the propagation of the disease, for it has been ascertained that the
species of mosquito which serves as an intermediate host for the yellow
fever germ may breed in cesspools and sewers, as well as in stagnant
pools of water. If, therefore, the streets of a city are unpaved and
ungraded and there are open spaces where water may accumulate in pools,
as well as open cesspools to serve as breeding places for _Culex
fasciatus_, the city will present conditions more favorable for the
propagation of yellow fever than it would if well paved and drained and
sewered.

The question whether yellow fever may be transmitted by any other
species of mosquito than _Culex fasciatus_ has not been determined.
Facts r