PROPHYLAXIS OF MALARIA. 
31 
but for convenience of description I shall refer to them as the male 
and female gamete respectively. 
While no true development of the gametes occurs within man, 
if blood containing them be removed from the body, the male gamete 
frequently undergoes flagellation and liberates the micro gametes, a 
process normallv occurring in the middle intestine of the mosquito. 
In very rare instances the fertilization of the female gamete by one 
of these microgametes may be observed in the blood after removal 
from the body, but this can only be regarded as an accidental occur¬ 
rence, as it normally occurs only within the infected mosquito. The 
differentiation of the sexual forms or gametes is not a very diffi¬ 
cult matter, although the opposite opinion appears to be generally 
prevalent. The estivo-autumnal gametes , because of their crescentic 
shape when fully developed, are easily recognized, even bv a novice 
in malarial parasitology, but the intracorpuscular stages in the de¬ 
velopment of the gametes of all of the species of plasmodia are more 
difficult of recognition, although with a clear knowledge of their 
morphology and a little practice all of the stages of development 
may be differentiated in stained preparations of blood. The fully 
developed gametes of Plasmodium vivax (the tertian plasmodium) 
and of Plasmodium malarias (the quartan plasmodium) are easily 
differentiated if one is acquainted with their morphology. 
In considering the morphology of the gametes it will be necessary 
to describe that of each species, as observed in both fresh and stained 
specimens of blood. The description given will include only the 
salient diagnostic points, and will be found true of the vast majority 
of organisms, although frequent deviations will be observed due to 
artefacts produced during the staining process or to developmental 
anomalies brought about by adverse conditions in the human host. 
(The stain used was Wright’s modification of the Romanowsky 
method, already described.) 
The gametes of Plasmodium vivax (the tertian plasmodium). 
Fresh preparations. —In fresh preparations it is practically impos¬ 
sible to distinguish the gametes of Plasmodium vivax from the 
forms of the human life cycle until they are fully developed. While 
individual gametes may contain a larger amount of pigment, which 
is coarser in structure, this distinction can not always be made. How¬ 
ever, when the gametes are fully developed they may be easily dis¬ 
tinguished, even when unstained, from the fully developed forms of 
the human cvcle, and the male and female forms can be readily dif- 
ferentiated. 
The male Gamete or Microgametocyte. —The living microgamet- 
ocyte of Plasmodium vivax , when fully developed, measures from 
8 to 10 microns in diameter, and almost fills the infected red cor¬ 
puscle; it is spherical in shape and is more or less filled with dark 
