PROPHYLAXIS OF MALARIA. 
23 
tion occurs; the pigment becomes collected near the center or to one 
side of the plasmodium in the form of a compact clump or clumps, 
and fine radial striations are observed extending from the center 
toward the periphery of the plasmodium, dividing it into several 
ovoid segments or spores. As a rule, these spores, in the tertian 
plasmodium, are arranged in two rows, one row surrounding the 
center of the plasmodium and another surrounding the first row; 
but often the spores are arranged irregularly and are always devoid 
of pigment. They vary in number from 12 to 24, or even more, but 
the average is from 16 to 20. The spores are known as merozoites 
and when free in the blood plasma measure from one-fifth to 2 mi¬ 
crons in diameter, are oval in shape, hyaline in appearance, and 
present a spherical, refractive center, and a less refractive mass of 
protoplasm surround it. The merozoites are capable of infecting the 
red blood corpuscles and thus the human life cycle of the plasmo¬ 
dium is continued. 
EXPLANATION OF PLATE 1. 
Figure 1.— Plasmodium , vivax. (Tertian plasmodium.) Young forms or tlie 
so-called “ring forms.” Wright’s stain. X 1200. 
Figure 2. —Plasmodium vivax. Quarter-grown parasite. Wright’s stain. X 1200. 
Figure 3.— Plasmodium -vivax. Half-grown parasite. Wright’s stain. X 1500. 
Figure 4.— Plasmodium vivax. Three-quarters-grown parasite. Wright’s stain. 
X 1S00. 
EXPLANATION OF PLATE 2. 
Figure 1.— Plasmodium vivax. (Tertian plasmodium.) Pre-sporulating para¬ 
site. Wright’s stain. X 1800. 
Figure 2.— Plasmodium vivax. Sporulating parasite. Wright’s stain. X 1200. 
Figure 3.— Plasmodium vivax. Sporulating parasite. Wright’s stain. X 1800. 
Figure 4.— Plasmodium vivax. Sporulating parasite. Wright’s stain. X 1800. 
EXPLANATION OF PLATE 3. 
Figure 1.— Plasmodium vivax. (Tertian plasmodium.) Free spores or mero¬ 
zoites. Wright’s stain. X 1200. 
Figure 2.— Plasmodium vivax. Fully developed macrogametocyte of Plasmo¬ 
dium vivax. X 1800. 
Figure 3. — Plasmodium vivax. Fully developed micro gametocyte of Plasmo¬ 
dium vivax. Wright’s stain. X 1800. 
Figure 4. —Plasmodium vivax. Atypical parasite, resembling the parthenoge- 
nctic macrogametes described by Schaudinn. Wright’s stain. 
X 1500. 
In preparations stained with Wright’s stain, the youngest form 
of Plasmodium vivax appears in the red cell as the so-called “ ring 
form*' consisting of a delicate ring of cytoplasm stained a robin’s- 
egg blue, at one portion of which is a ruby-red dot of chromatin, the 
ring inclosing an unstained area through which the salmon or pink 
of the corpuscle is visible. In those plasmodia in which ameboid 
