48 
MALARIA 
by Ross (1903). It is placed near one end 
of the slide and may be made in either of 
two ways. The first method is to touch the 
under surface of the slide to a large, rotund 
drop of blood and, without losing contact 
with the drop or touching the slide to the 
finger, move the slide in narrow circles until 
the blood on the slide covers an area about 
the size of a dime. Such a smear holds an 
amount of blood contained in 3 to 5 average 
drops. The second method is to place sev¬ 
eral average drops of blood quite near each 
other and then, with the needle or the cor¬ 
ner of a clean slide, quickly puddle these 
into one fairly homogeneous drop about the 
size of a dime. Practice soon teaches one 
the amount of blood to take to assure suffi¬ 
cient thickness and yet prevent crackling 
and peeling of the blood when dry. A satis¬ 
factory thick film is several layers of 
erythrocytes thick in the middle and thins 
at the extreme edge to a one layer thickness. 
Thick and thin smears on the same slide. 
It is often and perhaps usually desirable to 
have a thick and a thin film on opposite 
ends of the same slide. This permits the 
number or identifying character to be writ¬ 
ten with pencil in a part of the thin film. 
If the thick only is taken, a wax pencil may 
be used to make the label on the end of the 
slide opposite the blood film. 
Drying. Thick films should always be 
dried in a horizontal position to assure even 
distribution of the blood. All blood films 
should be protected from dust and insects, 
especially house flies. Slides taken in the 
field should be placed film side down in a 
slide box (held vertically as previously de¬ 
scribed) to prevent dust from falling into 
the wet film. They should be sent as soon 
as visibly dry to the laboratory for staining, 
for age or summer heat will prevent perfect 
staining of thick films. If thick films are 
air-dried, several hours’ desiccation seems 
necessary to effect complete adherence of 
the smear to the slide. Drying may be 
hastened by placing in an incubator at 37° 
C for a short time, or by a blast of warm 
air from an electric hand hair dryer held 
not too close to the wet films (Young 1938). 
Direct heat must be avoided, for like alco¬ 
hol it “fixes” the red blood cells and pre¬ 
vents dehemoglobinization, so necessary in 
thick film staining. 
Stains. The most dependable stain, par¬ 
ticularly for thick films, is obtained with a 
good quality of Giemsa stain diluted with 
distilled water of a pH from 7.0 to 7.2. 
Grubler’s dyes have long given complete 
satisfaction in this work (Beck 1911). 
The imminence of a European war and then 
its actual existence gave rise recently to the 
study of American dyes in order to produce 
stains consistently satisfactory on malarial 
parasites, particularly in thick films. In 
this study, it was found that Azure B, not 
Azure A, is the principal ingredient of 
German Azure I. With this knowledge as 
a basis, formulae were devised for the com¬ 
pounding of satisfactory Giemsa solutions 
(formula “A” below) (Roe, Lillie and 
Wilcox 1940). To make these entirely reli¬ 
able, however, Azure B should be added to 
the list of certified dyes, with its dye con¬ 
tent determined. It is hoped and expected 
that this step will soon be taken. In the 
absence of certified Azure B, and in order 
to facilitate the manufacture of Giemsa 
stain from American dyes, another study 
was made to devise a Giemsa stain from the 
eosinates of Azure A, Azure B, and Methy¬ 
lene Blue, since the eosinates are easily 
made and are of uniform composition and 
dye content (Roe, Wilcox and Lillie, in 
Plate I— Phases of Malarial Parasites in the Mosquito Host 
1. P. vivax. Stomach of A. quadrimaculatus with heavy cyst infection. Cysts about 35 micra in diam¬ 
eter, 15 days old. 
2. P. vivax cyst about 4 micra in diameter, 3 days old. Pigment clearly discernible. 
3. P. vivax eysts 6 to 8 micra in diameter, 7 days old. Pigment clearly discernible. 
4. P. vivax cysts 13 days old. Sporoblast formation well advanced, some pigment still visible. 
5. P. vivax. Optical equatorial section of nearly mature cyst, showing developing sporozoites projecting 
from sporoblasts. Same specimen as Fig. 1. 
6. P. vivax. Nearly mature cyst in higher focus. Rosette arrangement of developing sporozoites char¬ 
acteristic. Same specimen as Fig. 1. 
