22 



appeared from England. This would naturally reduce the 

 number of infected individuals and thus lessen the chance 

 of the Anopheles becoming infected. 



" (<r) It is possible that the use of quinine has reduced 

 the chances of infecting the Anoplieles through checking 

 the development of the parasites in the blood of subjects 

 affected with ague. 



" Of these, the first-mentioned cause seems to have been chiefly 

 operative. 



" 6. Since the geographical distribution of Anopheles in England 

 is wider than the former distribution of ague in this 

 countr\-, we are forced to conclude that it is not a matter 

 (if the geographical distribution of Anoplieles as much as 

 of their numerical distribution. 



" 7. Our observations having pro\ed the existence oi Anopheles 

 in non-malarious districts, we believe that they will explain 

 the occasional occurrence of ague in out-of-the-way 

 places, without making it necessary to assume that 

 malaria-bearing mosquitoes have been freshly-imported, 

 for, given suitable conditions of temperature and the 

 requisite number of Anopheles, i\ malarious subject coming 

 from other parts might well infect the local insects, which 

 in turn would spread the infection to healthy persons. 



