28 
PROPHYLAXIS OP MALARIA. 
collects in a small perfectly spherical mass at the center of the para¬ 
site, and radial striations may be detected dividing it into from 16 
to 18 very minute round or oval segments, or merozoites. While in 
infections with the tertian and quartan plasmodia it is often almost 
impossible to distinguish the remains of the red corpuscle when 
sporulation occurs, in this species it can be plainly seen that sporu- 
lation occurs before the corpuscle is entirely destroyed, as the sporu- 
lating organism occupies less than half of the cytoplasm of the red 
cell. 
In stained specimens this species presents the same staining reac¬ 
tions as the other malaria plasmodia, but differentiation is compara¬ 
tively easy owing to the minute size of this organism. 
The morphology of the various malaria parasites so far described 
is that peculiar to the forms that develop alone in man , but in every 
variety of malarial infection certain forms of the plasmodia are 
noted that are intended to complete their life cycle within the mos¬ 
quito, and which, so far as definite evidence now goes, never com- 
EXPLANATION OF PLATE 6. 
Figure 1.— Plasmodium falciparum. (Estivo-autumnal plasmodium.) Yovmg 
parasites. The so-called “ ring forms.” Wright’s stain. X 1200. 
Figure 2 .—Plasmodium falciparum. Speculating parasite and several young 
“ ring forms.” Wright’s stain. X 1800. 
Figure 3 .—Plasmodium falciparum. Speculating parasite. Wright’s stain. 
X 1800. 
Figure 4 .—Plasmodium falciparum. Free spores or merozoites. Wright’s stain. 
X 1500. 
plete a life cycle within man. These forms are known as gametes 
and probably develop from sporozoites in answer to certain influences 
produced upon the schizonts by life within man. While certain 
authorities believe that the gametes are introduced as such by the 
mosquitoes or develop from certain differentiated sporozoites , the 
great mass of evidence is in favor of their development within man 
from certain schizonts , for it is well known that they do not appear 
until an infection has lasted for several days, and never appear if the 
infection is properly treated. These forms will now be described, 
but before doing so it will be necessary to briefly sketch the life cycle 
of the malarial plasmodia within the mosquito in order to under¬ 
stand the names applied to the various stages during this cycle of 
development. 
Development of the malaria plasmodia within the mosquito 
(Sporogony or mosquito cycle). —In tertian and quartan infections 
certain of the plasmodia are observed that do not sporulate, but 
remain unchanged in the blood of man until they are removed, when 
changes occur that normally should occur in the stomach of the 
