296 The Philippine Journal of Science 1915 
Before proceeding to a summary of our data regarding the 
relation of malaria to topography, it may be well to examine 
the data on certain severe epidemics which have followed the 
introduction of large bodies of laborers into malarious regions 
in the Philippines. Three cases occurring in recent years are 
given in Table IX. 
All of these localities are in breeding places of Anopheles 
febrifer, and the epidemics occurred at seasons when the breed- 
ing of any stream species of anopheles was not materially inter- 
fered with by freshets or drought. In every case there were 
species of anopheles other than A. febrifer and A. maculatus 
present, but of these only A. rossi and A. barbirostris occurred 
in any numbers. 
The epidemic of malaria which occurred on the Manila—Baguio 
turnpike in Nueva Ecija during the construction of a bridge 
over Baliuag River merits a more detailed description. Mr. A. 
W. Austin, district engineer, who had charge of the work kindly _ 
gave us the following information. The epidemic occurred 
during the months of November and December, 1912, and of 
January, February, and March, 1913. Some thousands of ap- 
parently healthy men, many of them from nonmalarious regions, 
were brought into a camp on the banks of the river. Some 
lived in temporary grass huts on an area of dry gravel in the 
bed of the stream itself. Malaria was so severe that it was 
necessary to keep 2,400 men on the payroll in order to keep 
800 men at work. In one instance, of 300 men who turned out 
to work in the morning, only 18 were able to work until noon. 
The number of deaths is difficult to estimate, since many died 
after returning to their homes, but probably the number of fatal 
cases went into the hundreds. 
This locality was surveyed by Barber on December 31, 1914. 
The river at this point flows through a plain mostly covered 
with grass, but with low trees especially near the river. There 
are no swamps of any kind near. The stream is small, being 
more like a brook than a river. The water is clear, and flows 
with alternate swifter and slower stretches. The bed of the 
stream is gravelly, and there is much flow in the gravel below the 
surface. There is some vegetation at the margin of the stream, 
but the banks are cleaner than in the case of many streams 
examined by us in the Philippines. In a number of places, how- 
ever, coarse grass extends from the margin into the water. At 
one such place at the former site of the camp A. febrifer was 
found in abundance, sometimes 8 or more larve would be brought 
up at one dip of the collecting pan. Anopheles febrifer was 
