217 
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. 
