MALARIAL FEVERS 245 



falling sick with fever, as a result of " exposure to the 

 night air." What has already been said makes it ap- 

 pear extremely probable that the " night air/'/^r se, is 

 no more dangerous than the day air, but that the real 

 danger consists in the presence of infected mosquitoes 

 of a species which seeks its food at night. As pointed 

 out by King, in his paper already referred to, it has 

 repeatedly been claimed by travellers in malarious 

 regions that sleeping under a mosquito-bar is an 

 effectual method of prophylaxis against intermittent 

 fevers. 



An experiment on a larger scale has since been 

 made by some medical officers of the Japanese army 

 on the island of Formosa, where two companies of 

 soldiers were stationed in a very malarious locality. 

 The men of one company were carefully protected 

 from the bites of mosquitoes and did not suffer attacks 

 of malarial fever, while those of the other company, 

 who were not protected from mosquito bites, suffered 

 severely. 



The geographic distribution of the malarial fevers 

 is coextensive with the conditions favourable for the 

 development of the mosquito which serves as an inter- 

 mediate host of the parasites to which the disease is 

 due. Accordingly we find that these fevers prevail in 

 tropical regions, where there is abundant moisture, 

 in all parts of the world ; and in temperate regions, 



