48 MANUAL OF HUMAN PROTOZOA 



ing such oocysts is kept in a covered container at room 

 temperature, the spore formation is completed within the 

 oocyst in about 48 hours. At the end of the first day, the 

 oocyst contents divide into two sporoblasts (Fig. 12, 3) 

 and by the end of another day each sporoblast develops 

 into a spore, measuring 10-16m long by 7-10m broad (Fig. 

 12, 4). Each spore contains four sporozoites and residual 



r\ /^, ^- 



^"^' 



Fig. 12. Isospora hominis, unstained. X 1150. (original) 



1. A young oocyst. 



2. An oocyst in whfch the protoplasmic mass has contracted. 



3. An oocyst with two sporoblasts, one of which shows the 



division of contents. 



4. A mature oocyst with two tetrazoic spores. 



masses. Further changes would take place when the oocyst 

 finds its way into the human intestine in contaminated food 

 or water. 



This coccidian has been observed in Europe, North and 

 South America, Africa, and Asia, but appears not to be 

 of common occurrence. It is a cytozoic parasite in the 

 intestinal epithelium and may be considered as pathogenic. 

 However, no definite information on the effect (coccidio- 

 sis) of this organism upon human host is available except 



