82 DISEASES DUE TO PROTOZOA 



development of the parasitic oocyst in the body of the mosquito. If 

 it is below i5°-i6° C. no further development is said to take place. 

 L. malarias is said to require the highest temperature, P. vivax the 

 lowest, and P. malarise will develop at low or medium temperatures. 

 These differences may account for the unequal distribution of the 

 parasites and for their lesser danger in sub-tropical and temperate 

 climates. 



For details of the habits, &c., of mosquitoes, see article at the end 

 of the present one. 



MAN. 



Man is the third essential factor for the spread of malaria ; without 

 him, as far as is known, malaria cannot exist. 



The native population in the tropics forms the great reservoir of 

 parasites, but Europeans may also carry large numbers of gametocytes. 



A new district should always be investigated with regard to malaria 

 and the following facts ascertained : — 



(i) The diagnosis of the causative parasite. 



(2) The population of the area under consideration. 



(3) The average number of infected persons, ascertained by the 

 spleen rate. 



(4) The average number of persons having gametocytes in the 

 blood. 



(5) The species of Anophelinse and their breeding places. 



(6) The species which carry the parasite. 



(7) The species in which the parasite is found. 



(8) The number of Anophelines in the infected area. 



DISTRIBUTION AND CLIMATOLOGY. 



Malaria is most prevalent in the region of the Equator, 63° N. — ■ 



Regions that were once deadly may become salubrious, e.g., 

 England, Germany, Austria-Hungary. On the contrary, countries 

 once free may become infected, e.g., Mauritius, which was said to be 

 infected during the sixties of last century by the introduction of carry- 

 ing mosquitoes (Ross). 



The West Coast of Africa, from Senegal to the Congo, is perhaps 

 the worst malarial country in the world. 



India is heavily infected, especially about the swampy lands at the 

 foot of the Himalayas. 



It is also found in the following countries : Borneo, Arabia, Syria, 

 Siam, China, Western Australia, New Guinea, Solomon Islands, 

 Bismarck Archipelago, Central America, West Indies, Mexican Gulf, 

 the north of South America, Brazil, Paraguay, Bolivia, Colombia, 



