north is comparatively trifling, while in the south and 

 the islands it is severe. 



Here the difference may be due to differences in 

 climate, but this explanation does not suffice in the 

 examples in India we have mentioned. 



Again, we have great irregularities in the dis- 

 tribution of the species of parasite. The quartan, 

 for instance, in the Duars (Bengal) is exceedingly 

 common amongst the native children, but in Lahore 

 it is rare. 



Similar differences have been noted in Algeria, 

 where over large areas the quartan parasite is extremely 

 rare, yet in a few localities it occurs in seventy per 

 cent, of cases (Billet). 



So in India, as a whole, we have certain small 

 areas where malaria is intense, e.g., the Duars, Jeypore 

 (Madras), and Kanara (Bombay) (Christy), where we 

 also find blackwater fever ; yet in others, as in the 

 Central Provinces, where apparently all the conditions 

 are favourable, we have only a moderate intensity. 



We require, then, to examine carefully the 

 endemic indices over large areas in order to get an 

 accurate idea of the variations in endemic malaria. 



Further, after having established these broad data, 

 it will be necessary to make a close survey of each 

 individual district in order to endeavour to explain 

 the factors at work. 



