196 The Philippine Journal of Science 1915 
and to protect the preparations against cockroaches or ants, 
which will eat the blood on exposed slides. As a rule, the 
slides reached the laboratory in time to be stained within three 
days after collection. 
At the laboratory the slides were labeled and stained, the 
data on the slips and the results of the examination were entered 
in a book, so that it was possible to compare the results obtained 
from a given individual with those made at a later examination. 
The names of children positive for malarial parasites were re- 
ported to the principal of schools in order that treatment might 
be given these cases. In staining, the thin portion of the slide 
was fixed in methy! alcohol and dried. Then, with no fixing 
or other treatment of the thick smear, the slide was immersed 
for about one hour in staining jars containing Giemsa-Ro- 
manowski stain 1 part to 40 parts of water. The stained pre- 
parations were rinsed in distilled water, dried, and examined 
under the oil immersion without a cover glass. 
In determining the presence of parasites, we depended largely 
on the thick film, although the thin was used where comparison 
or confirmatory evidence was needed. The examinations were 
nearly all made by Barber and Guzman, both of whom had had 
a long previous training in examining thin smears for malaria 
in the tropics and in comparing the appearance of parasites in 
the thick smears with that in the thin smears. 
In most of our preparations the hemoglobin was well laked 
out by the watery stain and the parasites stood out clearly against 
the bluish or purplish background between the leucocytes. As 
a rule, both the cytoplasm and the chromatin of the parasites 
stained fully as well in the thick as in the corresponding thin 
smear, or even better. We found that much depends on the char- 
acter of the water used in diluting the stain. Spring or tap 
water laked out the blood well, but the parasites sometimes failed 
to take a good stain. Distilled water without the addition of 
some alkali often stained the background too red. We got our 
best results with rain water or a mixture of rain water with 
distilled water. Bacteria in water, especially from the bottom 
of a container, sometimes occur in numbers sufficient to obscure 
the background, and sometimes animalcules breed in water which 
might possibly be confused with some blood parasites. To avoid 
these we usually autoclaved the fresh or comparatively bacteria- 
free rain or distilled water and kept it in bottles ready for use. 
Chromatin granules, or red chromatinlike granules, not associated 
with the blue cytoplasm were never counted as parasites. 
The thick-film method in the examination of blood for parasites, 
