YELLOW FEVER 259 



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 

 then 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 mos- 

 quito 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 breed- 

 ing-places for Stegomyia fasciatus, that city will pre- 

 sent conditions more favourable for the propagation 

 of yellow fever than it would if well paved and 

 drained and sewered. 



It will be remembered that the malarial fevers are 

 contracted as a result of inoculation by mosquitoes 



