362 



PROTOZOOLOGY 



precystic form, 8-20/i in diameter, resembles that of E. histolytica. 

 Separation of the two species of amoebae by this stage is ordinarily 

 impossible. 



The cyst is spherical or often ovoid, highly refractile; 10-30^ in 

 diameter; immature cyst contains 1, 2 or 4 nuclei, one or more large 

 glycogen bodies with distinct outlines, but comparatively small 

 number of acicular, filamentous or irregular chromatoid bodies with 





■-0, 



,© 



X 







Fig. 169. Entamoeba coli, X1150 (Kudo). 1, a living amoeba; 2-5, 

 stained trophozoites; 3, an amoeba infected by Sphaerita; 6, a precystic 

 amoeba; 7, a fresh cyst; 8, a stained young cyst with a large glycogen 

 vacuole; 9, a stained mature cyst. 



sharply pointed extremities; when mature the cyst contains 8 

 nuclei and a few or no chromatoid bodies. The trophozoites and 

 small number of cysts occur in diarrhoeic or semiformed faeces and 

 the formed faeces contain cysts only. 



This amoeba lives in the lumen of the colon and does not enter the 

 tissues of the wall. As noted above, it has been observed in a few 

 instances to ingest erythrocytes, but there is no evidence to show 

 that it takes them in from living tissues. This amoeba is therefore 

 considered as a commensal. The abundant occurrence of the tro- 

 phozoite in diarrhoeic faeces is to be looked upon as a result and not 

 the cause of the intestinal disturbance. This amoeba is of common 

 occurrence and widely distributed throughout the world. 



