MORPHOLOGY, LIFE CYCLE AND PHYSIOLOGY OF P. VIVAX 
35 
Mitosis 
Another question which may be asked 
concerns the mechanism of division. Is it 
mitotic or otherwise? This is also still an 
unsettled problem, although Schaudinn 
many years ago (1902-03) described a 
modified mitosis in P. vivax. Several other 
authors ( e.g., Ivanic 1935, 1937) have made 
the same claim since. Unfortunately, how¬ 
ever, malarial parasites are difficult to 
stain with dyes such as haematoxylin, and 
the dyes ordinarily used do not give re¬ 
sults good enough for careful cytological 
study, particularly when the preparations 
have been made from air-dried smears. 
Obviously the very small size of malarial 
parasites (especially in sections) adds to 
the difficulty. In this connection reference 
may be made to studies on the Feulgen re¬ 
action of the malarial parasites, particu¬ 
larly those of Pawan (1931), Jirovec and 
Cerny (1932), Breindl and Jirovec (1932), 
and Ungo-Mugdan (1938). Pawan found 
that thymonucleic acid (nuclein) was ab¬ 
sent, thus differentiating the malarial para¬ 
sites from most other protozoa. Breindl 
and Jirovec demonstrated the presence of 
this form of nuclear chromatin in dividing 
forms (P. falciparum) and sporocysts 
and sporozoites (P. relictum), while Ungo- 
Mugdan found the reaction slightly 
positive in schizonts and strongly positive 
in exoerythrocytic stages of P. gallina- 
ceum. While these results do not agree, 
they do suggest that the nucleus of the ma¬ 
larial plasmodja may be different in nature 
from that of other protozoa during much, 
if not all, of the life-history, and perhaps 
the difficulty with which the parasites take 
ordinary stains is due to this fact. 
Effect of Parasites on Host-Cell 
There is also tiie matter of the way in 
which parasites of the species under con¬ 
sideration affect the host erythrocyte, and 
the question of whether the plasmodia are 
within or on the surface of the cell. It is 
now almost universally believed that they 
are intracellular, and all that is known of 
the behavior of the parasites is consistent 
with this view. Ratcliffe (1927) showed 
that when very thin sections were made of 
clots of parasitized blood the parasites gen¬ 
erally appeared within the cell boundaries, 
and this was true not only in the case of 
Plasmodium vivax but of P. falciparum 
and P. praecox (relictum ) also. Addi¬ 
tional evidence for this conclusion is the 
fact that the anti-malarial drugs of proved 
value seem to possess a favorable partition 
coefficient in all cases in which the problem 
has been studied (Hegner, Shaw and Man- 
well 1928; Shaw 1928). They are, in other 
words, substances which are capable of 
selective absorption by the red cell. 
The effect of the parasite on the cell 
which it invades is pronounced and very 
characteristic in the case of P. vivax. Even 
while the plasmodium is still small there 
often appear the well-known Schiiffner’s 
dots in the cytoplasm of the host cell (Fig. 
10). These are chromophilic particles 
which take a reddish tint when stained by 
Giemsa, or one of the other Romanowsky 
stains. What the nature of these dots is 
remains uncertain, but it has been sug¬ 
gested that they are of reticular origin, 
perhaps arising from basophil granules. 
In any case they are found only in vivax- 
infected erythrocytes, although they may 
be occasionally absent. It is said by some 
Explanation of Plate II 
16. Several oocysts on the gut wall of a mosquito. Magnification 1200 diameters. 
17. A multinucleated body found in a bone marrow smear of the sternum of a patient infected with 
Plasmodium vivax. This and the following figure are redrawn from Raffaele. jQ-937 ),. who 
interpreted them as pigment-free stages corresponding to those previously found in various 
species of avian malaria. He states that they occurred in cells of the reticulo-endothelial system. 
18. Two young trophozoites in a reticulo-endothelial cell. 
19. This schema shows the relationship of the five series of parasites belonging to the erythrocytic cycle, 
according to Boyd (1935b). The individual figures have been redrawn from those of Boyd, and 
indicate the various types of nuclei characterizing the parasites of the different series. The 
arrangement and the diagrammatic figures of schizonts are the author’s. 
