98 Capt. L. Rogers — Malaria North of Calcutta. [July, 1900.] 



fear that Bengal will not have its malaria much reduced by Ross* 

 ingenious suggestions. If, too, all malaria is due to the bites of these 

 mosquitos and they are present in such great numbers in the minimal 

 fever season, how many will be found in the maximal fever period, and 

 how great will be the difficulty of destroying them ? 



It may be objected that possibly many of the anopheles found by 

 me in the tanks were varieties which do not carry malaria, but until 

 we know which are harmless and can easily distinguish them at a 

 glance, this will not lessen the' difficulty of destroying the really 

 dangerous ones, if indeed any of them are harmless. 



The importance of the action of a filtered water supply in greatly 

 reducing the amount of malaria, which has been demonstrated in this 

 paper, is enhanced by the great difficulty of destroying the malaria- 

 bearing mosquito, and also raises the question as to whether these 

 insects may not carry the infection from cases of fever back to the 

 water of tanks, etc., and the disease may not commonly be obtained by 

 drinking such infected water, which has for centuries been considered 

 to be a frequent medium through which the disease may be obtained. 

 This important question can only be settled by experiment, which I 

 hope shortly to be able to undertake. 



Lastly, many charts have been made showing the monthly number 

 of fever cases treated in the dispensaries of this area together with the 

 monthly rainfall. It appears from these that the conditio*.:? which in- 

 fluence the amount of fever in different years is a general one, for all the 

 dispensaries show very similar curves in the same year ( except when 

 the water supply has been materially altered as in the case of Garulia) 

 so that some general cause must have been in operation. On the other 

 hand, there is no definite relationship between low or heavy annual 

 rainfall and the amount of fever, as I have shown elsewhere is the 

 case on laterite soil witli rapid ground water variations. There does, 

 however, seem to be some relationship between the daily distribution 

 of the rain and the amount of fever, but my observations on this point 

 are not sufficiently advanced to allow of any definite statement on the 

 subject at present. 



The broad result of the present inquiry, then, is simply that 

 there is a very definite relationship between the drinking water and the 

 amount of malaria, as judged by the spleen rate in this alluvial area. 



