19 
circulation. In addition, there are parasites whose contour blends 
with the protoplasm of the leucocyte and appears to be unprovided 
with a cyst (ph ii). Free parasites, some of which are large and 
oval in shape (pi. ii), are also abundant. 
The multiplication of the parasite takes place in a liver cell. The 
earliest stage is a small spherical form 10 micra in diameter, with a 
large vesicular nucleus composed of chromatin granules in a fino- 
mesh work, and a large karyosome. It is embedded in the protoplasm 
of the liver cell, the nucleus of the latter being pushed to one side. 
The cavit}" formed in the liver cell is fidly occupied by the parasite. 
As development proceeds the parasite increases in size and the nucleus 
divides into two. This stage is known as schizogony and the para- 
site becomes a scliizont. Many small, round granules are found in 
the latter when viewed in the fresh condition. The two nuclei 
divide and subdivide until from 12 to 20 daughter nuclei are formed. 
The schizont increases in size and the liver cell becomes a mere shell, 
the nucleus of which, after undergoing the changes characteristic of 
degeneration, finally disappears. A delicate cyst wall is formed 
around the developing schizont, which, at maturity, is ovoid and 
measures, on the average, 25 b}^ 30 micra. Some, however, are larger 
and may measure 28 by 35 micra. 
The nuclei of the schizont are arranged at the two extremities, as 
shown in longitudinal sections (pi. iii). In fresh cysts studied at 
this stage the central mass of protoplasm is granular, with a clear 
area at the ends. At a later stage short rods of clear protoplasm, 
each containing a nucleus, are seen at the poles. These rods 
increase in length, the proximal extremities growing toward one 
another; the central granular mass diminishes in size. Eventually 
the clear rod-shaped bodies have become fully grown merozoites and 
occupy the entire cyst except for a small granular ‘‘rest” body. 
MTien the merozoites are fully grown, the cyst containing them 
becomes soft and gelatinous; later it ruptures and the merozoites 
escape, becoming free moving vermicules. The number of mero- 
zoites is from 12 to 20; the average 16. 
In scrapings made from the cut surface of a liver in which the 
schizonts and c^^sts are numerous, their structure and the ease with 
which they are ruptured is readily determined. In sections from 
tissue, fixed and embedded in the usual method, the contents of the 
cyst shrink to a greater degree than the liver tissue and artificial 
spaces are formed around the schizonts (pi. iii, fig. 1). 
In heavily infected livers the number of cysts is very large. Their 
presence is associated with extensive fatty changes in the liver 
parenchyma. '\Ahen a small piece of fresh liver tissue is spread 
out thinly between slide and cover slip and examined with the micro- 
scope on a warm stage, the contents of the ripe cysts are seen to be in 
