PROPHYLAXIS OF MALARIA. 
29 
mosquito. These bodies are circular in shape when fully developed 
and can be differentiated in both the living condition and in stained 
preparations. Likewise, in the estivo-autumnal infections certain 
bodies are developed, of typical crescentic shape, the so-called “ cres¬ 
cents," that only undergo development within the mosquito. These 
bodies while in the blood of man are known as gametes and are 
sexually differentiated, the male being known as the microgame- 
tocyte and the female as the macrogametocyte. When they reach 
the stomach of the mosquito the male, or microgametocyte, liberates 
liagella, which are known as microgametes, and which serve to fer¬ 
tilize the female macro gametocyte , which, after certain maturation 
phenomena, is now known as the macrogamete. This process may 
rarely be observed in preparations of blood removed some time from 
the body if a little moisture be present on the slide and the tempera¬ 
ture be suitable. The fertilization of the macrogamete occurs nor¬ 
mally in the middle intestine of the mosquito and the result of the 
fertilization is known as the sporont. After a certain period of 
time the sporont elongates and becomes motile and is then known as 
the ookinete. The ookinete penetrates the wall of the middle intestine 
of the mosquito and eventually becomes situated between the adi¬ 
pose tissue and the muscular wall of the intestine. Here the organ¬ 
ism becomes circular in shape and forms a cyst known as the oocyst. 
At this stage the cytoplasm is reticular and granular in appearance, 
the pigment is reduced in amount, and the entire organism is inclosed 
in a well-defined capsule. The oocyst is formed at about the third or 
fourth day after infection of the mosquito. About the fifth or sixth 
day the oocyst enlarges and within it are formed spherical refractive 
bodies known as sporoblasts. At this stage the organism is so greatly 
increased in size that it projects from the intestinal wall and may be 
seen with a low-power objective. At the end of a week the sporo¬ 
blasts have produced a large number of delicate filaments having 
pointed extremities and containing a small amount of chromatin, 
which are called sporozoites. They are about 14 microns in length and 
are arranged in a ray-like formation about a central mass in the 
sporoblast , which may contain pigment. The sporozoites are finally 
liberated in the body-cavity of the mosquito by the rupture of the cyst 
and make their way to the tubules of the salivary glands. At this 
time, if the infected mosquito bites a man, the sporozoites will be 
inoculated, taken up by the blood stream, and penetrating the red 
blood corpuscles, develop into schizonts and thus begin the human 
life cycle of plasmodia. The entire life cycle in the mosquito varies 
from 10 to 14 days in duration. 
Having thus briefly reviewed the mosquito-cycle of the malaria 
plasmodia, we will now consider the morphology of those fonns 
