462 The Philippine Journal of Science 1921 
or possibly because of insufficient store of food supply. It was 
taken from the stool passed on March 16, that had been in the 
ice box at 10° C. for forty-eight hours and had then been sealed 
on a slide in physiological salt solution. Another cyst (Plate 3, 
fig. 8), also abnormal, was found in the same preparation. 
As I have said, most of the cysts found in freshly passed 
faeces are in early zygote stages, but sporoblast stages are not 
infrequently found. However, I have seen no later stages in 
the fresh material. In his monograph, Dobell(3) says: “Devel- 
opment of the spores takes place outside the host and requires 
s veral days for its completion.” This is more or less in 
harmony with the behavior of cysts of other species of Isospora, 
and probably is the general rule with this species ; but it is not 
by any means invariable, as I have found on studying this case. 
Certain factors may intervene to yield cysts in the infective stage 
at a much earlier period. The bacteriological and general chem- 
ical and physical conditions, as oxygen supply, in the fsecal mass 
probably play an important part, as may also a state of constipa- 
tion which delays the passage of the cysts. For instance: The 
stool passed at 8.45 a. m., on March 16, consisted of two distinct 
portions — a normal, formed, brown mass and another portion, 
passed after it, that was greenish brown and soft in consistence. 
It was immediately examined, and both portions were found to 
contain oocysts in an early stage of development. 
The stool was examined again the following day at 4.30 p. m., 
approximately thirty-two hours after its passage. The temper- 
ature during this time had varied between 28° C. and 30° C. The 
formed portion of the stool contained undeveloped zygotes, 
sporoblasts, sporocysts, and a number of fully developed cysts 
and some that were degenerated (Plate 2, fig. 7). The softer 
portion of the stool yielded no fully developed cysts. A few cysts 
were seen that had gone as far as sporoblast development, but 
there were many cysts that clearly were undergoing degener- 
ative changes. 
Of course, this is only an isolated case, but it does show that 
under certain conditions the cysts may become infective in con- 
siderably under two days, a fact that must be taken into consid- 
eration in the epidemiology of the disease. The preservation 
of the cysts in the formed portion of the stool was excellent. A 
specimen of the material was examined on April 2, after it had 
rested in a bottle on the laboratory shelf since it was passed, 
and was found to contain numerous, fully developed and healthy- 
looking cysts. 
