274 
MALARIA 
lected all lie between tbe Madden Dam and 
the eastern boundary of tbe Panama Canal 
Zone, and are situated on tbe banks or 
tributaries of tbe Chagres River. Tbe 
towns of Santa Rosa, Guayabalito and 
Gatuncillo are on tbe right (north) bank 
of tbe river; Las Guacas lies opposite Santa 
Rosa on tbe left bank, at tbe junction of tbe 
Cbagres and its Moja Polio tributary. This 
latter town is almost surrounded by water 
full of aquatic vegetation, making ideal con¬ 
ditions for anopheles mosquito breeding. 
In February, 1937, tbe town of Agua Clara 
was added to the number of towns under 
observation. This town dates from 1936, 
when a group of people who formerly lived 
on Gatun Lake cleared tbe jungle from 
several hilltops just across tbe eastern 
boundary of tbe Canal Zone at boundary 
marker No. 50. Tbe elevation of this town 
is about 100 feet, and tbe distance from 
Santa Rosa is about one and one-half miles. 
During these investigations, we used 
chiefly tbe population located along tbe 
Madden Highway, in tbe towns of Cbilibre, 
Aguas Buenas, and Buenos Aires as con¬ 
trols. These towns are located about 5 miles 
to tbe south of tbe left bank of tbe Cbagres 
River, and about 150 feet higher than tbe 
river towns. 
Tbe populations of just such rural areas 
as these in which our observations were 
made are tbe sources from which large 
business organizations must draw their 
labor forces. 
Survey Methods 
Blood parasite surveys made monthly in 
all villages during tbe ten-year period have 
been used to measure our results. Tbe 
thick-film technique of Barber and Komp 
(1929b) has been used throughout tbe 
period, and tbe staining and examination 
of tbe films has been done by experienced 
technicians, most of whom have been with 
us throughout tbe experiment. It was 
found that not all tbe inhabitants of tbe 
villages could be surveyed at any one sur¬ 
vey during tbe month, but during the days 
for tbe period of treatment and during in¬ 
spections, we were able to collect blood-films 
from all tbe permanent inhabitants. Tbe 
migratory habits of some of our people have 
been a source of much inconvenience to us. 
It was impossible to examine or treat indi¬ 
viduals adequately who did not reside per¬ 
manently in tbe towns, and such persons 
might be undiscovered carriers of sexual 
malarial parasites, capable of infecting 
mosquitoes. 
Treatment Methods 
During tbe first year of our observations 
(Sept. 1930-Aug. 1931) we used quinine 
sulphate in all villages. A native Pana¬ 
manian graduate nurse (assisted by school 
teachers and tbe corregidors (mayors) of 
tbe villages) was supplied with tbe list of 
names of those found positive in each 
monthly survey. Twenty grains (1.29 gm) 
of quinine sulphate to each positive per day 
for a period of 10 days constituted a course 
of treatment during tbe first year. 
During tbe second year (Sept. 1931-Aug. 
1932) quinine was used in tbe same manner, 
but in addition, plasmochin simplex in 
doses of 0.01 gm twice a week was given to 
all positives in all tbe villages under treat¬ 
ment except New San Juan. 
During the third year (Sept. 1932-Aug. 
1933) , quinine sulphate was used in tbe 
same dosage throughout the year in New 
San Juan, but in tbe four other villages 
under treatment we used quinine sulphate 
during tbe first 4 months, and atabrine 0.1 
gm three times a day for 5 days from Janu¬ 
ary 1933 to August 1933. 
During this latter period, one of us 
(W. H. W. K.) stayed a week during each 
month in the villages, and personally ad¬ 
ministered the atabrine to all those found 
positive in the preceding monthly surveys. 
It is only during this period that we are 
absolutely sure that the drug was adminis¬ 
tered according to schedule. It is well to 
mention that during this period blood-films 
were taken at the completion of treatment 
from all persons who received the drug; in 
every case but one these films were negative 
for asexual parasites at the end of the 5-day 
course of atabrine. Crescents, which are 
