60 
MALARIA 
of 36 to 40 hours, (b) Stage seldom seen in 
peripheral blood. Very small, solid, with one small 
mass of chromatin; lightly staining, compact cyto¬ 
plasm; and with the very dark pigment usually 
collected in one small, dense block, (c) One mass 
of chromatin, often elongated, frequently less defi¬ 
nite in outline than that of vivax. Cytoplasm dense, 
compact with few irregularities of outline; in 
rounded, oblong or sometimes band shape. Pig¬ 
ment granules larger, darker than in vivax with 
great tendency toward peripheral arrangement. 
Fills or almost fills normal cell, (d) Resembles 
closely same stage of P. malariae, but is consider¬ 
ably larger. Pigment is lighter in color and less 
conspicuous. 
Presegmenting schisont. (a) Chromatin divided 
into a number of masses; cytoplasm shows varying 
degrees of separation into strands and particles; 
pigment shows tendency to collect in parts of the 
parasite, (b) When found in peripheral blood this 
stage resembles the same stage of P. malariae but 
is smaller and the pigment is likely to be completely 
clumped in one small dark mass, (c) Same as 
vivax except that the parasite is smaller and shows 
fewer divisions of chromatin, as it approaches seg¬ 
mentation. (d) About 25% of infected cells are 
definitely of oval shape. Usual picture is that of 
a round parasite in center of an oval cell. Many 
cells with indefinite fringed outline. Pigment 
lighter in color and less coarse than in P. malariae. 
Segmenting schisont. (a) 12 to 24 divisions or 
merozoites, composed of a dot of chromatin and a 
portion of cytoplasm. The pigment is in one or 
two clumps. Parasite practically fills enlarged cell, 
(b) 8 to 24 merozoites, which are very small com¬ 
pared to those of other species. Rarely found in 
peripheral blood. Fills about two-thirds of normal¬ 
sized cell, (c) 6 to 12, usually 8 or 10 merozoites 
in a rosette or irregular cluster. Practically fills 
normal-sized cell, (d) Usually 8 merozoites ar¬ 
ranged around a central block of pigment. 
Macrogametocyte. (a) Dark blue, homogeneous 
cytoplasm with no vacuoles; small, compact, dark 
red, usually eccentric chromatin; abundant dark 
brown pigment scattered through cytoplasm. When 
grown usually fills or nearly fills enlarged cell. The 
outline is circular or ovoid and regular, (b) Cyto¬ 
plasm possibly a deeper blue than in microgameto-. 
eyte. Usually single dark red chromatin mass near 
center associated with concentrated aggregation of 
pigment, darker than in microgametocyte. Cres¬ 
centic or sausage-shaped about 1| times diameter 
of erythrocyte in length, possibly longer and more 
slender than microgametocyte. (e) Cytoplasm and 
chromatin same as vivax. Pigment is abundant, 
dark brown, coarser than in vivax. When grown 
usually fills the normal-sized cell. Outline circular 
or ovoid, (d) Distinguished from P. malariae by 
size of infected cells and by Sehiiffner’s dots. Less 
easy to differentiate from vivax. Seldom or never 
contained in an oval erythrocyte. 
Microgametocyte. (a) Light blue, gray, pink or 
almost colorless cytoplasm; large diffuse light red 
or pink chromatin—usually centrally placed, often 
with vesicular area around chromatin mass. Abun¬ 
dant yellowish-brown pigment throughout cyto¬ 
plasm. When grown, about size of a normal cell. 
Usually circular in outline, (b) Often the cyto¬ 
plasm is paler than in macrogametocyte—grayish 
blue or pink. Loose, diffuse, light staining gran¬ 
ules or threads of chromatin scattered with 
numerous granules of pigment throughout central 
half or more of parasite. Parasite possibly 
broader, shorter, and with more rounded ends than 
those of macrogametocyte. (e) Same as vivax ex¬ 
cept in size. When grown, fills or almost fills 
normal-sized cell, (d) Distinguished from P. ma¬ 
lariae by size of infected cells and by Sehiiffner's 
dots. Less easy to differentiate from vivax. Sel¬ 
dom or never contained in oval erythrocyte. 
Stages in peripheral blood, (b) Usually ring 
form trophozoites and gametoeytes. Other stages 
rarely found except in severe cases. 
Remarks, (a) More stages of growth likely to 
be seen in one film than in other species. Gameto- 
cytes appear early in cycle, (b) Parasites fre¬ 
quently more numerous than in other infections. 
Unlike other species—growth of asexual forms, fol¬ 
lowing the ring stage, take place in internal organs, 
(e) Parasites are usually more compact and hence 
appear more intensely stained than those of other 
common species. Gametoeytes rarer than in other 
species, appear late. Least often found of 3 spe¬ 
cies in United States, (d) Species not found to 
date in United States. Differentiation not possible 
in thick films. 
In thick films, stained as recommended, 
the erythrocyte outlines are destroyed by 
lysis, leaving a background which varies 
from clear light blue to mottled gray-blue, 
often in anemic bloods clouded with nuclear 
and reticular remains of immature erythro¬ 
cytes. Against this background is seen the 
familiar purple or violet nuclei of the leuko¬ 
cytes, sometimes with ragged cytoplasm. 
The neutrophilic granules are indistinct or 
absent, eosinophilic granules are usually re¬ 
tained with characteristic color, and plate¬ 
lets appear singly or in groups with dis¬ 
tinctive texture and more or less hazy 
outline. White cells containing malarial 
pigment are much more easily found in the 
thick film than in the thin film. 
In the thick film, the parasite, minus the 
cell wall, has much the same appearance as 
in the thin film, except that it may seem 
smaller and more shrunken in the thicker 
portion of the smear. The thin edge of the 
thick film resembles the thin film so closely 
that it is very valuable to the technician 
