230 The Philippine Journal of Science 1915 
of the towns which show a high parasite index are situated in 
coconut regions. Such regions are by no means always ma- 
larious. Much of the coast of Cebu, where the bulk of the pop- 
ulation is found, is lined by coconut trees. Few of these towns 
have allowed the coconut groves to relapse into jungle. Factors 
which favor the dispersal and shelter of mature anopheles must 
be considered as well as the presence of breeding places; and 
given sufficient numbers of the proper mosquito carriers, jungle 
and other overgrowth favor the development of malaria in a 
community. 
In summarizing the results by type of locality, we find that 
as a rule low-lying coast towns in which the high tide extends 
into the streams well among or back of the houses show little 
or no malaria. Paranaque, Orion, and the swampier portions 
of Manila are good types of towns of this class. In or near 
these three localities A. rossii was found breeding in abundance, 
but no case of malaria was found in over 700 children examined. 
Cases of malaria contracted in Manila are few, if, indeed, they 
ever occur. We have questioned many physicians of the city, 
and have examined suspicious fever cases obtained in houses 
or in clinics and have found but few cases positive for malaria, 
and those almost always gave a history of residence in some 
other locality, usually a malarious one. The positive cases found 
in routine examination at the laboratory of the Philippine Gen- 
eral Hospital at Manila nearly always show a history of origin 
of the disease outside of the city. Large cities usually show 
a lower rate than rural communities. 
Bentley '§ states that even small towns of Bengal, India, al- 
though intensely malarious, may present areas in their centers 
nearly malaria free. With a fixed number of anopheles carriers 
the rate tends to fall as the population increases. However, the 
portions of Manila examined are for the most part immediately 
contiguous to swamps or ponds, and if A. rossi were a carrier we 
would expect at least a small positive spleen or parasite index. 
Mangarin in Mindoro and Limay in Bataan Province are ex- 
ceptions to the rule that low coast towns are malaria free. Man- 
garin, which shows a parasite index of 39.3, is situated on a flat 
swampy coast. In the dry season there is no fresh flowing 
water within a kilometer. From the nature of the country it 
is probable that fresh streams are found much nearer to the 
town in the wet season. Palangeran River flows into the sea 
*% Ind. Journ. Med. Res. (1914), 4, suppl. 78. 
