34 
PROPHYLAXIS OF MALARIA. 
almost black in color, occurs in the form of minute rods, and is 
arranged in irregular masses near the periphery or in a wreath about 
the center of the organism. 
The tertian microgametocyte may be distinguished from the mac- 
rogametocyte , in stained specimens, by the pale blue staining of the 
cytoplasm as compared with the deep blue of the macrogametocyte , 
the larger amount of chromatin, collected in masses and surrounded 
by an achromatic zone, and the presence of several irregular masses 
of chromatin, situated near the periphery, when the organism is 
about the flagellate. In the young gametes it is impossible to dis¬ 
tinguish between the male and female forms, except by the stain¬ 
ing reaction of the cytoplasm, the male staining a very pale blue, 
while the female stains a deep blue. 
The gametes of Plasmodium malaria (the Quartan Plasmo¬ 
dium).—The gametes of Plasmodium malaria are very similar to 
those of Plasmodium vivax , which have just been described, and 
for this reason require no extended description. Allowing for the 
difference in the size of the two species, the staining reactions, and 
the differentiation of the male and the female forms are practically 
identical, and the description of one can be used for the other if it 
be remembered that the quartan gametes , at every stage of develop¬ 
ment, are much smaller than the tertian. 
The gametes of the estivo-autumnal plasmodia .—The sexual 
forms, or gametes , of Plasmodium falciparum and Plasmodium fal¬ 
ciparum quotidianum are commonly known as “ crescents,” and are 
easily distinguished from any other form of plasmodium. The 
presence of these crescents in the blood at once stamps the individual 
as a “ carrier ” of malaria, but the early stages of the estivo-autum- 
nal gametes are not crescentic in shape, and at this time it is im¬ 
possible to differentiate them from the quartan gametes , as they 
are similar in structure and in size. When fully developed the cres¬ 
cents are easilv recognized, and the male and female forms can be 
differentiated with little trouble. 
What has been said regarding the appearance of gametes of ter¬ 
tian malaria in the earlier stages of development is equally true of 
the gametes of the estivo-autumnal plasmodia, and it is only after 
they have assumed the crescentic shape that they can be said to 
differ in morphology from the tertian or quartan gametes , if we 
except their size, which is slightly smaller than the quartan and 
much smaller than the tertian gamete. It will not be necessary, 
then, to describe the early stages of development of these bodies, but 
only their morphology after the typical crescentic shape has been 
acquired. This occurs while the parasites are still within the in¬ 
fected red. corpuscle, and as the organism gradually enlarges the 
infected cell shrinks about it, forming an envelope, which is most 
