54 



of the patients have died). We must not, therefore, expect 

 to see malaria vanish, as if by magic, immediately after 

 our campaign against mosquitoes. Certainly bad out- 

 breaks, such as those which often occur amongst soldiers 

 and labourers, ought to cease fairly abruptly, provided that 

 the areas concerned have been properly dealt with ; but 

 old cases will still linger on, and old residents will continue 

 to suffer from their weekly or monthly " go of fever." Of 

 course, sceptics will point to this continuance of the disease 

 and will claim that it disproves the mosquito theory ; but 

 this will not be a fair argument, for the reasons just 

 given. 



On the other hand, as soon as the mosquitoes are 

 appreciably reduced in number, we may reasonably expect 

 a parallel reduction in the number of fresh infections. In 

 very malarious countries, almost all the resident adults 

 have been infected at one time or another ; so that the 

 appearance of fever in these is often due to relapses. 

 Hence, in such localities, we can only gauge the number of 

 fresh infections in people who arrive from non-malarious 

 countries, and in newly born children. The latter will 

 afford an excellent means of judging the decrease of 

 malaria by an accurate process. KOCH discovered that in 

 malarious places a very large percentage of the native 

 children possess the parasites of malaria in the blood, even 

 a few months after birth. If, then, we can show that this 

 percentage decreases after our operations against mos- 

 quitoes, we shall be able to prove the good effect of the 

 measure by an exact method. The method is one, how- 

 ever, which can only be employed by a well-instructed 

 medical man. 



