THE DETECTION AND DIFFERENTIAL DIAGNOSIS 
OF MALARIAL PARASITES IN THE SCHIZOG- 
ONOUS AND SPOROGONOUS CYCLES 
By AIMEE WILCOX 
NATIONAL INSTITUTE OF HEALTH, WASHINGTON, D. C. 
LUCILE LOGAN 
STATION FOR MALARIA RESEARCH, TALLAHASSEE, FLA. 
I. DETECTION OF PARASITES 
Schizogonous Cycle 
The microscopical detection of malarial 
parasites in stained blood films is the most 
reliable and accurate method of laboratory 
diagnosis thus far devised. For accurate 
results with either the thin or thick film 
techniques, special materials and pro¬ 
cedures have been found highly desirable, 
since the best efforts of a qualified micro- 
scopist may be frustrated by poor condition 
of the specimen. 
Slides. For the preparation of blood 
films new slides are preferable and these 
should be thoroughly cleaned. In order to 
avoid touching the surface of the clean slide 
in handling, it should be grasped by the 
edges. To prevent annoyance and loss of 
time in field surveys and to facilitate filing 
of slides in the laboratory, the slides should 
be of a length and thickness to fit easily into 
regular or special slide boxes (Barber and 
Komp 1929b). The slides used should be 
clear, unscratched, non-corrosive, and above 
all meticulously clean, i.e., free from grease, 
dust, acid or alkali, with measurements of 
75 mm x 25 mm x 1.25 mm. These require¬ 
ments are met in a slide the equivalent of 
No. 7030-B of A. H. Thomas Company. 
Other materials. For field work, in addi¬ 
tion to clean slides, the materials necessary 
are a supply of small gauze squares or a roll 
of absorbent cotton, alcohol for cleansing, a 
needle for pricking (preferably with a 
pyramidal point), wax pencils for number¬ 
ing the slides, a supply of wooden slide 
boxes with capacity of 25 each or special 
field boxes holding 100 slides horizontally, 
and record forms or cards (Komp 1933). 
An inverted “T” block, against which two 
of the small slide boxes may be held upright 
with a rubber band while blood smears are 
being made, is a great convenience in sup¬ 
porting and preventing the tipping of boxes 
of wet films. This block may be made of 
two pieces of soft wood 3\" wide and 1" 
thick; the upright 6" long fastened at right 
angles in the center of the horizontal piece 
which is about 8" long. A carrying kit for 
this equipment is convenient. 
Making smear. The skin surface to be 
pricked, preferably of the finger, should be 
well cleansed by a pledget of cotton or small 
piece of gauze moistened with alcohol to 
remove grease, perspiration or dirt, and 
then should be dried with a fresh piece of 
cotton or gauze so that residual alcohol will 
not mix with the blood drop. The puncture 
should be deep enough to allow a free flow 
of blood under gentle pressure. The first 
blood to exude should be wiped off. 
Thin smear. To make a thin film, a small 
drop of blood is collected on the face of a 
slide near one end. The end of a second, 
or “spreader,” slide (preferably with a 
narrower end), is lowered onto the face of 
the first, in an inclined position slightly in 
advance of the drop so as to make an angle 
of about 30°, and is then drawn back 
against the blood which spreads out at the 
line of contact. Then with a rapid even 
motion the film is made by pushing the 
spreader toward the other end of the slide. 
A good thin film should show the erythro¬ 
cytes well separated with no overlapping 
or massing. 
Thick film. The thick film was devised 
