multiplication. The same authority states':— 



"The more we learn about these diseases, the less important in 

 its bearing on the geographical distribution, and as a direct 

 pathogenic agency, becomes the role of temperat ure j,,-,- xp, and the 

 more the influence of the tropical fauna." 



Malaria for instance is by far the most important disease 

 agency found in the tropics and sub-tropics, undermining 

 the health of multitudes and predisposing to other diseases, 

 and as to its source in native villages, Sir Patrick Manson 2 

 refers to the Anopheles mosquito which having bitten a 

 person with infected blood, then becomes affected by the 

 Plasmodium malar ice, and after biting other persons it 

 infects them also with the disease. He says :— 



"After some years, and after many re-inoculations by infected 

 mosquitoes, the surviving original inhabitants gradually acquire 

 immunity from malaria, and the parasite can no longer be found 

 in the blood. . . Children born in the village have no immunity, 

 and therefore, soon after birth, bein^ bitten by the infected Ano- 

 pheles, acquire the infection. In this way there is kept up in the 

 village a permanent stock of infected Anopheles." 



Dr. W. H. Deaderick says — 



" It is evident that if this cycle be broken at any point, infec- 

 tion rannot occur, and that if it were universally interrupted 

 during a sufficiently long period of time the disease would be 

 annihilated." 



The author also refers to the success attending efforts to 

 suppress the disease at Ismailia, where it was introduced 

 in 1877, and made great headway during the period 1885- 

 1902, but since 1903 the cases have fallen to 2°» only of 

 the annual average for 1885-1902. 



Sir Patrick Manson says also, 4 " That there is a protec- 

 tive power in the human body against the Plasmodium is 



1 "Tropical Diseases," p. xv. 2 Op. cit., p. 102. 



