THE MORPHOLOGY, LIFE CYCLE AND PHYSI¬ 
OLOGY OF PLASMODIUM FALCIPARUM 
By S. F. KITCHEN 
INTEENATIONAL HEALTH DIVISION, ROCKEFELLER FOUNDATION, TALLAHASSEE, FLA. 
Morphology 
The schizogonous and sporogonous cycles 
of this parasite are depicted in Fig. 1. 
Reproduction of this parasite is accom¬ 
plished in two ways, either by an asexual 
or by a sexual process. There i§ no accepta¬ 
ble proof of the occurrence of binary fission 
or parthenogenesis among the malaria plas- 
modia. 
Schizogonous Cycle 
Asexual reproduction of the plasmodium 
occurs through schizogony in the intermedi¬ 
ate host, man. This type of multiplication 
involves repeated division of the nucleus, 
with division of the cytoplasm about each 
daughter nucleus. Following release of the 
merozoites, or daughter cells, those which 
survive attach themselves to erythrocytes 
and develop in the peripheral circulation 
until they are somewhat more than half 
grown. They then accumulate in the capil¬ 
laries of the viscera, and here undergo schi¬ 
zogony. Thus, less than half of the schi¬ 
zogonous cycle is spent in the peripheral 
circulation and the parasite may go through 
an indefinite number of such asexual cycles. 
Trophozoites. The merozoites, the young¬ 
est forms of this series, seldom in our ex¬ 
perience, find their way into the peripheral 
circulation. They are smaller than in the 
other species and usually exhibit no vacu¬ 
ole ; their diameter hardly ever exceeds one 
micron and generally it is less than that. 
Young “ring forms” are usually the first 
to be found, and it is these that are fre¬ 
quently characteristic of this species of plas¬ 
modium. They are often quite delicate in 
appearance, the cytoplasm consisting of a 
slender circle of blue cytoplasm (Wright or 
Giemsa stain), sometimes so fine that it can 
barely be seen, enclosing a vacuole. The 
chromatin, too, is commonly characteristic. 
It may be present as a small red dot which 
appears to be placed upon the outer surface 
of the ring. On the other hand it may take 
the shape of a small red bar, bent or 
straight, the thickness of which is greater 
than that of the thread-like cytoplasm. Not 
infrequently the size of the dot, however, 
appears quite out of proportion to the slen¬ 
derness of the band of cytoplasm. Often 
(and practically diagnostic of this species 
when present) the chromatin is multiply 
represented by two or more small dots 
which may lie closely together or on oppo¬ 
site sides of the small, fine cytoplasmic ring. 
Characteristically, too, is the common obser¬ 
vation of two or more, possibly as many as 
five or six, rings in one erythrocyte. Not 
infrequently these young forms are found, 
as it seems, ‘ ‘ applied ’ ’ to the circumference 
of the erythrocyte so that one may see in the 
stained smears only a short, thin streak of 
blue cytoplasm seemingly lying on the 
periphery of the red cell and surmounted 
by a red dot of chromatin, hence the terms, 
“accole” or “applique.” Occasionally the 
thread of cytoplasm will be seen to be looped 
over an indentation in the outline of the 
erythrocyte. Such appearances naturally 
raise the perplexing question (a long stand¬ 
ing but still unsettled one) as to whether 
the young parasites are intra- or extra- 
corpuscular. A vacuole is not evident in 
these forms. As the parasite grows, one 
notices a thickening of the cytoplasm, which 
usually takes place first almost opposite the 
position of the chromatin dot. With the 
increase in size of the parasite, the amount 
of cytoplasm increases and the whole ring 
gradually thickens, though not necessarily 
symmetrically. Too, with the increase in 
amount of cytoplasm, irregularities in the 
shape of the parasite become apparent. 
The originally almost perfectly spherical 
