36 MANUAL OF HUMAN PROTOZOA 



'^' 8) are more rounded than living ones. The cytoplasm is 

 finely reticulated. The nucleus located close to the anterior 

 margin is spherical or pyriform, and composed of a large 

 endosome and a sharply defined membrane. The four 

 flagella take their origin in the anterior border of the 

 nucleus. 



Cysts 



1. Living specimens. The cyst is a small ovoid body, sur- 

 rounded by a distinct cyst wall. Its cytoplasm is homo- 

 geneous, and contains small granules. There are 1, 2, or 4 

 nuclei which are not easily seen in life. The cyst measures 

 6-8m by 4-6m. 



2. Stained specimens. The cyst wall is recognizable in 

 stained specimens. The nuclei become clearly visible. 

 Young cysts contain 1 or 2 nuclei (Fig. 8, ^), but mature 

 cysts show 4 nuclei (Fig. 8, 10). The nuclei are spherical 

 or ellipsoidal and highly vesicular, each with an endosome. 

 The refractile granules seen in life are somewhat eosin- 

 ophile. 



Some authors hold that this flagellate is the same as 

 EntevGmonas hominis in which the fourth flagellum was 

 overlooked. 



4. Chiloinastix niesnili (Wenyoii 1910) 



This is a somewhat larger flagellate which inhabits the 

 lumen of the colon and caecum. Some hold that it also 

 inhabits the lower small intestine. Its solid food is exclu- 

 sively bacteria and other microorganisms, and the organ- 

 ism is considered a commensal. The trophozoites and cysts 

 occur in diarrhoeic faeces, and the formed faeces contains 

 cysts only. 



