26 
MALARIA 
matin masses begin to appear (Young, 
Stubbs and Coatney 1940), at which time 
the parasite practically fills the host cell. 
Occasionally precocious multiplication of 
chromatin occurs so that quite young para¬ 
sites show multiple masses. 
According to Schaudinn (1902), the 
chromatin masses of P. vivax increase by 
nuclear division of a mitotic type. In 
studying the growth stages of P. malariae, 
we have noticed several characteristics 
which are not compatible with the general 
idea of mitosis. When stained with the 
Giemsa polychromatic stains, the new bodies 
of chromatin do not resemble the original 
chromatin mass. The new chromatin 
masses are often at opposite sides of the 
parasite and are much smaller than the 
original chromatin body, which does not 
suggest mitotic division. Also, the new 
masses do not stain as deeply or distinctly 
as the original mass, which suggests that 
they do not arise by fragmentation. 
Coatney and Young (1939) found that 
colchicine, which arrests division at the 
metaphase in many types of cells, had no 
effect on the division of P. relictum in 
pigeons, which might suggest the absence of 
an achromatic figure. 
Pawan (1931) using a modification of the 
Feulgen nuclear reaction was unable to 
demonstrate thymonucleic acid in the nu¬ 
cleus of P. vivax and P. falciparum. He 
concluded that the nuclei of these malarias 
differ chemically from the nuclei of certain 
other protozoa. 
From these observations it seems that the 
chromatin of malaria differs in chemical 
composition and in method of formation 
from the ordinary nuclear structures. 
By the 65th hour the host cell is com¬ 
pletely filled. The principal change, dur¬ 
ing this period, is the increase in the number 
of chromatin masses to about five. The 
pigment may increase and remains scat¬ 
tered throughout the cell. 
Between the 65th and 72d hours the de¬ 
finitive number of chromatin masses is 
formed. With the appearance of the final 
number, the cytoplasm begins to divide so 
that in the end each chromatin mass is sur¬ 
rounded by a small amount of cytoplasm. 
These new bodies are known as merozoites. 
During this process of segmentation, the 
pigment is extruded to the cleavage lines 
between the daughter masses of cytoplasm 
so that it often appears segregated in a 
radial fashion, or it may be clumped in a 
mass which is often in the center of the cell, 
together with the residuum of the cleavage 
process. A central mass of clumped pig¬ 
ment, surrounded by symmetrically ar¬ 
ranged merozoites, gives rise to the “ro¬ 
sette” arrangement characteristic of this 
species. The number of merozoites formed 
may be any number from 6 to 12, with an 
average of about 8. 
Coincident with the maturity of the 
asexual parasite, at approximately 72 hours, 
the red cell ruptures, liberating the mero¬ 
zoites, pigment, residual solids and other 
metabolic products into the blood stream. 
This segmentation occurs in the U. S. Pub¬ 
lic Health Service strain of quartan ma¬ 
laria between 9:00 a.m. and 3:00 p.m. 
(Young et al. 1940). In a synchronous 
infection all the parasites segment in about 
6 hours. The period that the merozoites 
remain free in the blood stream seems to be 
very short, for smears taken at the height 
of sporulation seldom reveal free forms. 
According to Knowles and Das Gupta 
(1930) the free merozoite phase is one hour 
in length. In our opinion, this seems to be 
a liberal estimate. 
Immediately after segmentation, ring 
forms can be found in the red cells. Just 
how the parasite enters the erythrocyte has 
not been described for this species. As the 
ring forms are about the same size and 
shape as the merozoites, it seems probable 
that the ring forms are derived from them. 
Hegner (1938) found that merozoites of 
P. malariae invaded reticulocytes 9.5 times 
as frequently as mature red cells, supposing 
both types were equally available. On the 
other hand, Kitchen (1939a) found rings in 
mature erythrocytes in both greater abso¬ 
lute and relative numbers than in reticulo¬ 
cytes. 
As yet there are few reports of an exo- 
erythrocytie phase of P. malariae. Jerace 
